Cardioverter-Defibrillators
Number: 0585
Table Of Contents
PolicyApplicable CPT / HCPCS / ICD-10 Codes
Background
References
Policy
Scope of Policy
This Clinical Policy Bulletin addresses cardioverter-defibrillators.
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Medical Necessity
Aetna considers the following interventions medically necessary when the following criteria are met:
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Implantable Cardioverter-Defibrillators
FDA-approved implantable cardioverter-defibrillators (thoracotomy and non-thoracotomy systems) for any of the following groups of individuals, except where contraindicated:
- Members after one or more episodes of spontaneously occurring and inducible ventricular fibrillation (VF), or syncopal or hypotensive ventricular tachycardia (VT) that is not associated with acute myocardial infarction (AMI)]; and not due to a remediable cause (e.g., drug toxicity, electrolyte abnormalities, ischemia); or
- Members after spontaneously occurring but non-inducible documented syncopal or hypotensive VT that was not due to AMI; or
- Members after VT/VF cardiac arrest that was not associated with an inducible ventricular arrhythmia, and not due to AMI; or
- Members with structural heart disease (such as prior myocardial infarction (MI), congenital heart disease, and/or ventricular dysfunction) and spontaneous, sustained VT (greater than 30 seconds), whether hemodynamically stable or unstable; or
- Members with sustained VT (greater than 30 seconds) and normal or near-normal ventricular function; or
- Members after unexplained syncope, which by history and clinical circumstances was probably due to a ventricular tachyarrhythmia, with either of the following:
- The presence of reproducible inducible syncopal or hypotensive VT or VF that is not associated with AMI and not due to a remediable cause, and in whom antiarrhythmic medications are ineffective, not tolerated, or contraindicated, and where catheter ablation has failed or is not possible; or
- Significant left ventricular (LV) dysfunction (LV ejection fraction less than 50 %), and structural heart disease such as prior myocardial infarction (MI), congenital heart disease, and/or ventricular dysfunction; or
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Members with ischemic dilated cardiomyopathyFootnote1* with any one of the following:
- New York Heart Association (NYHA) Class II or III heart failure (see Appendix) with a LVEF less than or equal to 35 %, who are at least 40 days post MI, and are on optimal medical therapy, defined as 3 months of maximally titrated doses as tolerated of an ACE inhibitor, beta-blocker, and diuretic, and are at least 90 days post-revascularization (e.g., CABG, PCI with angioplasty and/or stenting); or
- NYHA Class I heart failure (see Appendix) with a LVEF less than or equal to 30 %, who are at least 40 days post MI, are on optimum medical therapy, and are at least 90 days post-revascularization (e.g., CABG, PCI with angioplasty and/or stenting); or
- Non-sustained VT due to prior MI, and LVEF less than or equal to 40 %, and inducible VF or sustained VT at EP study performed at least 96 hours after revascularization or MI; or
- Members with non-ischemic dilated cardiomyopathy, NYHA Class II or III heart failure (see Appendix), and a left ventricular ejection fraction (LVEF) less than or equal to 35 % who are on optimal medical therapy, defined as 3 months of maximally titrated doses as tolerated of an ACE inhibitor, beta-blocker, and diuretic; or
- Members with familial or inherited conditions with a high-risk of life-threatening ventricular tachyarrhythmias, including:
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Long QT syndrome with either of the following:
- Syncope and/or VT while receiving beta-blockers; or
- Asymptomatic with one or more of the following risk factors for sudden cardiac death:
- QTc greater than 500 msec, or
- LQT2 or LQT3; or
- Family history of sudden death
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Hypertrophic cardiomyopathy or arrhythmogenic right ventricular cardiomyopathy (ARVC) with one or more of the following risk factors for sudden cardiac death:
- Documented VT; or
- Family history of sudden cardiac death in at least one first-degree relative; or
- Left ventricular thickness of 3 cm or greater; or
- Hypotensive response to exercise treadmill testing (ETT); or
- At least one episode of unheralded syncope within the previous 12 months.
- Catecholaminergic polymorphic VT who have syncope and/or documented sustained VT while receiving beta-blockers.
- Brugada Syndrome who have had syncope or who have documented or inducible VT.
- LV non-compaction cardiomyopathy with either of the following:
- Positive family history of sudden cardiac death; or
- Impaired left ventricular ejection fraction (less than 50 %)
- Cardiac sarcoidosis, giant cell myocarditis, or Chagas disease, regardless of LV ejection fraction
- ICD implantation may be considered in affected members with a familial cardiomyopathy associated with sudden death.
Footnote1*Note: Ischemic cardiomyopathy is defined as left ventricular systolic dysfunction associated with marked stenosis (at least 75 % narrowing) of at least 1 of the 3 major coronary arteries, or a documented history of myocardial infarction.
Notes:
Aetna considers replacement of an implantable cardioverter defibrillator pulse generator and/or leads medically necessary when damaged, malfunctioning, when replacement is recommended according to the manufacturer's instructions in the product labeling, or due to a change in the member's medical condition.
Aetna considers implantable cardioverter-defibrillators experimental and investigational for other indications because its safety and effectiveness has not been established.
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Subcutaneous Cardioverter-Defibrillators
FDA-approved subcutaneous cardioverter-defibrillators for persons who meet medical necessity criteria for an implantable cardioverter defibrillator listed above and who do not have symptomatic bradycardia, incessant ventricular tachycardia, or spontaneous, frequently recurring ventricular tachycardia that is reliably terminated with anti-tachycardia pacing or who have previous endocarditis or infection associated with conventional implantable cardioverter-defibrillators.
Aetna considers subcutaneous cardioverter-defibrillators experimental and investigational for all other indications because their effectiveness and safety have not been established.
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Wearable and Non-Wearable Cardioverter-Defibrillators
Wearable cardioverter-defibrillators (WCDs) (automatic external cardioverter-defibrillators that are worn under the member's clothing) or nonwearable cardioverter-defibrillators as durable medical equipment (DME) only for members who meet any of the following criteria:
- A documented episode of VF or a sustained (lasting 30 seconds or longer) VT (these dysrhythmias may be either spontaneous or induced during an electrophysiologic (EP) study, but may not be due to a transient or reversible cause and not occur during the first 48 hours of an AMI); or
- A previously implanted defibrillator now requires explantation; or
- Member meets above-listed criteria for an ICD and is awaiting heart transplantation; or
- Member meets above-listed criteria for an ICD and has a systemic infectious process or other temporary condition that precludes ICD implantation; or
- Either documented prior myocardial infarction or dilated cardiomyopathy and a measured LVEF less than or equal to 35 %, in whom duration of decreased LVEF is less than 90 days, and recheck of LVEF is planned at 90 days. After the initial 90 day approval, an extension on a month-to-month basis may be obtained to bridge the time until automated implantable cardioverter defibrillator (AICD) implant or heart transplant, but the wearable device had no indication for extended usage if a destination therapy is not planned; or
- Familial or inherited conditions with a high risk of life-threatening VT such as long QT syndrome or hypertrophic cardiomyopathy; and
For non-wearable only, a caregiver will be present in the home and capable of operating the cardioverter-defibrillator.
Contraindications
Cardioverter-defibrillators are not considered medically necessary when other disease processes are present that clearly and severely limit the member's life expectancy.
Note: Electronic analysis of defibrillator systems is required for long-term routine follow-up care of cardioverter-defibrillators. Automatic defibrillator monitoring is considered medically necessary. Electrophysiologic assessment is a more complex evaluation of cardioverter-defibrillators, and is considered medically necessary.
Note: Intracardiac electrophysiological procedures performed before implantation of cardioverter-defibrillator may be done as an outpatient.
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Experimental and Investigational
Aetna considers the following interventions experimental and investigational because the effectiveness and safety of these approaches has not been established:
- ICDs with hemodynamic (fluid status) monitoring
- Use of implantable cardioverter-defibrillators in persons with left ventricular assist devices (LVADs)
- N-terminal pro-B type natriuretic peptide for assessing prognosis of cardioverter-defibrillator implantation.
- WCDs and non-wearable cardioverter-defibrillators for use after CABG or PTCA (in persons not meeting any of the above indications) or for all other indications.
- ICDs with hemodynamic (fluid status) monitoring
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Related Policies
Background
Cardiovascular mortality as a consequence of ventricular fibrillation (VF) or ventricular tachycardia (VT) continues to be a major health problem despite advances in the overall management of cardiovascular disease. Sudden cardiac death kills approximately 400,000 people per year. About 10 to 15 % of individuals who experience life threatening VT or VF recover, usually with an external cardiac defibrillator. These survivors have various therapeutic options such as anti-arrhythmic drugs, radiofrequency or surgical ablation of VT focus, or implantable cardioverter-defibrillators (ICDs).
Available literature indicates ICDs are now widely used for the secondary prevention of sudden cardiac death due to VF or VT. Ventricular tachycardia or VF can be secondary to a variety of conditions: progression in underlying pathology (i.e., deterioration of left ventricular [LV] function or worsening of coronary artery disease), autonomic imbalance, electrolyte abnormalities or even pharmacological intervention. The ICD is generally accepted as treatment for patients who have experienced an episode of VF not accompanied by an acute myocardial infarction or other transient or reversible causes (e.g., drug toxicity, electrolyte abnormalities, and ischemia). Additionally, accepted guidelines prefer this treatment in patients with sustained VT causing syncope or hemodynamic compromise. As primary prevention, the literature shows the ICD is superior to conventional anti-arrhythmic drug therapy in patients who have survived a myocardial infarction and who have spontaneous, non-sustained VT, a low ejection fraction, inducible VT at electrophysiological study, and whose VT is not suppressed by procainamide.
A number of well-designed studies have shown the effectiveness of the ICD in high-risk patients who have already experienced a myocardial infarction (MI). Schlapfer and colleagues (2002) compared the long-term survival rates of patients with sustained ventricular tachyarrhythmia after MI who were treated according to the results of EP study either with amiodarone or an ICD. They found that the long-term survival of patients with sustained ventricular tachyarrhythmias after MI, with depressed LV function, is significantly better with an ICD than with amiodarone therapy, even when stratified according to the results of the EP study. In a randomized controlled study (n = 1,232) to evaluate the effect of an implantable defibrillator on survival of patients with reduced LV function after MI, Moss et al (2002) concluded that in patients with a prior MI and advanced LV dysfunction, prophylactic implantation of a defibrillator improves survival and should be considered as a recommended therapy.
The Multi-center Autonomic Defibrillator Implantation Trial II (MADIT II) was stopped early because of a 30 % reduction in mortality in patients randomized to receive an ICD (Coats, 2002). The 4-year multi-center trial of 1,200 patients was terminated early after an independent board observed that the post-MI patients with impaired LV function receiving the implantable defibrillator had improved survival rates compared to those receiving conventional treatment.
- patients with ischemic dilated cardiomyopathy (IDCM), documented prior MI, and a measured left ventricular ejection fraction (LVEF) of less than or equal to 35 %;
- patients with non-ischemic dilated cardiomyopathy (NIDCM) greater than 9 months with a measured EF less than or equal to 35 %.
In addition, according to CMS, several additional criteria must be met. Patients must not have: New York Heart Association (NYHA) Class IV heart failure; cardiogenic shock or symptomatic hypotension while in a stable baseline rhythm; coronary artery bypass graft or percutaneous transluminal coronary angioplasty within the past 3 months; acute myocardial infarction (AMI) within the past month; clinical symptoms or findings that would make them a candidate for coronary revascularization; irreversible brain damage from pre-existing cerebral disease; or any disease, other than cardiac disease (e.g., cancer, uremia, liver failure) associated with a likelihood of survival less than 1 year.
The Center for Medicare and Medicaid Services expanded coverage of ICDs to persons with NIDCM, based primarily on the results of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), a prospective randomized trial to determine whether amiodarone or an ICD will improve survival compared to placebo in patients with NYHA Class II and Class III heart failure and reduced LVEF less than 35 %. The study included persons with NIDCM and patients with ischemic dilated cardiomyopathy. A total of 2,521 patients were enrolled, 847 of whom were assigned to placebo plus conventional heart failure therapy, 845 to amiodarone plus conventional heart failure therapy, and 829 to single lead ICD plus conventional heart failure therapy. There was a significant reduction in all-cause mortality in the ICD group compared to the placebo group (hazard ratio compared to control = 0.77; 97.5 % confidence intervals [CI]: 0.62 to 0.96, p = 0.007). For patients with ischemic dilated cardiomyopathy, there was a reduction in mortality hazard ratio compared to control but it was not statistically significant (hazard ratio 0.79; 97.5 % CI: 0.60 to 1.04). For patients with NIDCM, there was a reduction in the mortality hazard ratio for ICD therapy compared to control but it was also not statistically significant (hazard ratio 0.73; 97.5 % CI: 0.50 to1.07). CMS noted that the absolute reduction in mortality was modest for a trial with a median follow-up of 45.5 months.
Patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) are characterized by progressive degeneration of the right ventricular myocardium, ventricular arrhythmias, fibrous-fatty replacement, and increased risk of sudden death. Mutations in 6 genes, including 4 encoding desmosomal proteins (junctional plakoglobin, desmoplakin, plakophilin 2, and desmoglein 2), have been identified in patients with ARVD/C. The potential use of genetic screening for desmoglein 2 mutations is for identifying persons at increased risk of ARVD/C who are candidates for prophylactic ICD. Currently, there are no prospective studies of the use of desmoglein 2 genetic testing for selecting ICD candidates. About one-third of individuals with ARVD/C have been reported to have mutations in the desmoglein 2 gene or other associated mutations (Franz et al, 2001), and it is unknown what proportion of asymptomatic persons who have desmoglein 2 mutations go on to develop ARVD/C. Thus, the risks and benefits of prophylactic ICD implantation in persons with mutations of this gene are unknown.
Automated external defibrillators (AED) (e.g., the HeartSine Samaritan PAD, HeartSine Technologies, Inc., San Clemente, CA; and the HeartStart Home OTC Defibrillator, Philips Medical Systems, Seattle, WA) are portable electronic devices that allow minimally trained individuals to provide electric shock to prevent death due to sudden cardiac arrest. These devices monitor heart rhythm and can, if needed, deliver an electric shock to the chest wall much like a traditional (paddle) defibrillator in a hospital. Automatic external defibrillators by lay persons have not been proven to reduce mortality compared to implantable cardioverter defibrillators or cardiopulmonary resuscitation by first responders.
An assessment on automated external defibrillators for home use published by Canadian Coordinating Office for Health Technology Assessment (Murray and Steffensen, 2005) concluded that no prospective studies showed that the use of automated external defibrillators in the home by untrained individuals improves health outcomes. The assessment stated that more research is needed to ascertain the benefit and harm of the home use of automated external defibrillators. The assessment of AEDs for home use found: “No prospective studies demonstrate that the use of AEDs in the home by untrained persons improves health outcomes. Further investigation is needed to determine the benefit and harm of AEDs in the home."
An assessment by the Ontario Ministry of Health and Long-term Care (MAS, 2005; Sharieff et al, 2007) reached similar conclusions, stating that further research is needed to examine the benefit of in-home use of automated external defibrillators in patients at high risk of cardiac arrest.
Marenco et al (2001) conducted a systematic review of the literature on the use of automatic external defibrillators (AEDs). Most of the literature on AEDs discusses their use by emergency medical technician or ambulance staff. The authors summarized the literature on use of AEDs by non-medical persons in the home:
Because the majority of cardiac arrests occur at home, several studies have examined the use of AEDs by family members of high-risk patients. Although these studies demonstrated the feasibility of training laypersons (e.g., family members) to use an AED, researchers had difficulty with patient recruitment and obtained disappointing results. There is mounting evidence for the efficacy of ICDs in patients at increased risk for sudden cardiac death. This has limited enthusiasm for the placement of AEDs in the home of high-risk patients and primarily limited the role of the AED in the home to high-risk patients who either refuse an ICD or have a contraindication to ICD placement. However, these studies used earlier-generation AEDs and, given the lower costs and ease of use of the current devices, further study with the newer technology is warranted.
Because there are no prospective clinical studies demonstrating that use of AEDs by non-medical persons for home use improves health outcomes, Aetna considers wearable automatic external cardioverter defibrillators (wearable cardioverter-defibrillators or WCDs) medically necessary only on an exception basis for high-risk patients who meet the criteria for an ICD and who either refuse an ICD or have a contraindication to ICD placement.
Epstein et al (2013) described usage of the WCD during mandated waiting periods following MI for patients perceived to be at high-risk for sudden cardiac arrest (SCA). These researchers evaluated characteristics of and outcomes for patients who had a WCD prescribed in the first 3 months post-MI. The WCD medical order registry was searched for patients who were coded as having had a "recent MI with ejection fraction less than or equal to 35 %" or given an International Classification of Diseases, 9th Revision 410.xx diagnostic code (acute MI), and then matched to device-recorded data. Between September 2005 and July 2011, a total of 8,453 unique patients (age of 62.7 ± 12.7 years, 73 % male) matched study criteria. A total of 133 patients (1.6 %) received 309 appropriate shocks. Of these patients, 91 % were resuscitated from a ventricular arrhythmia. For shocked patients, the LVEF was less than or equal to 30 % in 106, 30 % to 35 % in 17, greater than 36 % in 8, and not reported in 2 patients. Of the 38 % of patients not re-vascularized, 84 % had a LVEF less than or equal to 30 %; of the 62 % of patients re-vascularized, 77 % had a LVEF less than or equal to 30 %. The median time from the index MI to WCD therapy was 16 days. Of the treated patients, 75 % received treatment in the first month, and 96 % within the first 3 months of use. Shock success resulting in survival was 84 % in non-re-vascularized and 95 % in re-vascularized patients. The authors concluded that during the 40-day and 3-month waiting periods in patients post-MI, the WCD successfully treated SCA in 1.4 %, and the risk was highest in the first month of WCD use. The WCD may benefit individual patients selected for high risk of SCA early post-MI. The main drawback of this observational study was the lack of a control group. Additionally, quality-of-life data, cost-effectiveness and survival were not available in this study.
In an accompanying editorial of the afore-mentioned study, Zei (2013) stated that “A major limitation to this study is the selection bias inherent in the database used …. Another important limitation of this study is the lack of data about potential arrhythmia under-detection with the WCD … [T]his study still does not quite answer the elusive question of how to best risk-stratify post-MI low-EF patients in the early days after infarction”.
In a review on “Wearable cardioverter-defibrillators”, Adler et al (2013) stated that “The wearable defibrillator was not subjected to such rigorous trials, and it is not clear whether this device will significantly decrease total mortality (and not merely arrhythmic death) in patients with recent MI …. [W]hen the prescription of a wearable defibrillator is being considered, it should be kept in mind that there are no randomized, controlled studies showing that it provides survival benefit”.
The first multi-center randomized controlled clinical study to examine the use of at-home AEDs found that the devices do not improve overall survival when compared to conventional resuscitation methods, such as cardiopulmonary resuscitation (CPR). Bardy et al (2008) randomly assigned 7,001 patients with previous anterior-wall MI who were not candidates for an ICD to receive 1 of 2 responses to sudden cardiac arrest occurring at home: either the control response (calling emergency medical services and performing CPR) or the use of an AED, followed by calling emergency medical services and performing CPR. The primary outcome was death from any cause. The median age of the patients was 62 years; 17 % were women. The median follow-up was 37.3 months. Overall, 450 patients died: 228 of 3,506 patients (6.5 %) in the control group and 222 of 3,495 patients (6.4 %) in the AED group (hazard ratio, 0.97; 95 % CI: 0.81 to 1.17; p = 0.77). Mortality did not differ significantly in major pre-specified subgroups. Only 160 deaths (35.6 %) were considered to be from sudden cardiac arrest from tachyarrhythmia. Of these deaths, 117 occurred at home; 58 at-home events were witnessed. Automatic external defibrillators were used in 32 patients. Of these patients, 14 received an appropriate shock, and 4 survived to hospital discharge. There were no documented inappropriate shocks. The authors concluded that for survivors of anterior-wall MI who were not candidates for ICD, access to a home AED did not significantly improve overall survival, as compared with reliance on conventional resuscitation methods.
Exner (2009) stated that most sudden cardiac death (SCD) events occur in patients with less severe LV dysfunction, yet past trials and guidelines focus on those with severe LV dysfunction. Given the large pool of patients with less severe LV dysfunction and a modest risk of SCD, methods to identify those who might benefit from an ICD are needed. Observational studies indicate that abnormal cardiac repolarization and impaired autonomic function, especially in combination, appear to identify patients with less severe LV dysfunction at risk of SCD. Extensive scarring also appears to identify patients at risk. Ongoing and planned studies will better define the role of using non-invasive tests to select patients for ICD therapy. The author concluded that non-invasive measures of cardiac structure, autonomic function and myocardial substrate appear to be promising in identifying patients with less severe LV dysfunction at risk of SCD. However, it is unclear if ICD therapy will improve survival in these patients. Until definitive data from prospective, randomized trials are available it is premature to recommend use of these tools to guide ICD therapy.
Tsai et al (2009) noted that SCD among orthotopic heart transplant recipients is an important mechanism of death after cardiac transplantation. The role for ICDs in this population is not well-established. These researchers examined if ICDs are effective in preventing SCD in high-risk heart transplant recipients. They retrospectively analyzed the records of all orthotopic heart transplant patients who had ICD implantation between January 1995 and December 2005 at 5 heart transplant centers. A total of 36 patients were included in this study. The mean age at orthotopic heart transplant was 44 +/- 14 years, the majority being male (n = 29). The mean age at ICD implantation was 52 +/- 14 years, whereas the average time from orthotopic heart transplant to ICD implant was 8 +/- 6 years. The main indications for ICD implantation were severe allograft vasculopathy (n = 12), unexplained syncope (n = 9), history of cardiac arrest (n = 8), and severe left ventricular dysfunction (n = 7). Twenty-two shocks were delivered to 10 patients (28 %), of whom 8 (80 %) received 12 appropriate shocks for either rapid VT or VF. The shocks were effective in terminating the ventricular arrhythmias in all cases. Three (8 %) patients received 10 inappropriate shocks. Underlying allograft vasculopathy was present in 100 % (8 of 8) of patients who received appropriate ICD therapy. The authors concluded that use of ICDs after heart transplantation may be appropriate in selected high-risk patients. They stated that more studies are needed to establish an appropriate prevention strategy in this population.
The U.S. Food and Drug Administration (FDA) has approved the Subcutaneous Implantable Defibrillator (S-ICD) System (Cameron Health, San Clemente, CA) "to provide defibrillation therapy for the treatment of life-threatening ventricular tachyarrhythmias in patients who do not have symptomatic bradycardia, incessant ventricular~tachycardia, or spontaneous, frequently recurring ventricular tachycardia that is reliably terminated with antitachycardia pacing." The Subcutaneous Implantable Defibrillator (S-ICD) System uses a lead that is implanted just under the skin along the bottom of the rib cage and breast bone. The S-ICD System consists of: a titanium case containing a battery and electronic circuitry that provides defibrillation therapy and pacing at a rate of 50 beats per minute up to 30 seconds after a shock; a subcutaneous electrode which has a proximal and distal ring electrode on each side of a 3 inch (8 cm) defibrillation coil electrode; and accessories include an electrode insertion tool, programmer, telemetry wand, magnet, suture sleeve, torque wrench, and memory card. The FDA approval was based upon the results of a 321-patient study in which 304 patients were successfully implanted with the S-ICD System. At the time of implantation, the investigator tested the effectiveness of the device by inducing heart arrhythmias. The S-ICD System was successful at converting all abnormal heart rhythms that it detected back to normal rhythms. Investigators followed these patients for six months following implantation, during which time the device detected and recorded 78 spontaneous arrhythmias in 21 patients; all arrhythmias were either successfully converted back to normal by the defibrillator or resolved on their own. The FDA noted that, because the S-ICD System memory stores data from only the 22 most recent arrhythmia episodes, there may have been other detected episodes that could not be analyzed by investigators. The FDA reviewed safety data based on the entire 321-patient study population to identify complications that can occur during and after implantation of the S-ICD System. The most common complications included inappropriate shocks, discomfort, system infection, and electrode movement, which required repositioning. The FDA reported that 8 patients died during the study; however, experts (who were not involved with the study) could not definitively attribute the deaths to the S-ICD System. Eleven patients required the removal of the device, and 18 had discomfort that was resolved without repositioning the device or surgery. At the end of six months, more than 90 percent of patients had no complications. As part of the approval, FDA is requiring the manufacturing company to conduct a postmarket study to assess the long-term safety and performance of the device and to assess differences in effectiveness across genders. The study will follow 1,616 patients for five years. There is currenty insufficient published evidence of the effectiveness and safety of this device (Bardy et al, 2010; Gold et al, 2012; Jarman et al, 2012; Kobe et al, 2012).
Jarman and Todd (2013) described the early phase United Kingdom (UK) clinical experience with the S-ICD. A questionnaire was sent to all UK hospitals implanting S-ICDs. Nineteen of 25 (76 %) hospitals responded with the details of 111 implanted patients (median 5/hospital [range of 1 to 18]). Mean duration of follow-up was 12.7 ± 7.1 months. Median patient age was 33 years (range of 10 to 87 years). Underlying pathology was primary electrical disease in 43 %, congenital heart disease 12 %, hypertrophic cardiomyopathy 20 %, ischemic cardiomyopathy 14 %, idiopathic dilated cardiomyopathy 5 %, and other cardiomyopathies 7 % patients. Nineteen (17 %) patients required 20 re-operations, including permanent device explantation in 10 (9 %). Twenty-four appropriate shocks were delivered in 13 (12 %) patients, including 10 for VF. One patient suffered arrhythmic death, but there were no failures to detect or terminate ventricular arrhythmias above the programmed detection rate. Fifty-one inappropriate shocks were delivered in 17 (15 %) patients; 41 (80 %) were for T-wave over-sensing and 1 (2 %) for atrial flutter-wave over-sensing. The 11 patients who received inappropriate shocks due to T-wave over-sensing were significantly younger than patients who did not (24 ± 10 versus 37 ± 19 years; p = 0.02). The authors concluded that the S-ICD is an important innovation in ICD technology. However, these data indicated that adverse event rates were significant during early clinical adoption. Important lessons in patient selection, implant technique, and device programming could be learnt from this experience.
In a prospective, non-randomized, multi-center trial, Weiss et al (2013) evaluated the safety and effectiveness of the S-ICD System for the treatment of life-threatening ventricular arrhythmias (VT/VF). Adult patients with a standard indication for an ICD, who neither required pacing nor had documented pace-terminable VT, were included in this study. The primary safety end-point was the 180-day S-ICD System complication-free rate compared with a pre-specified performance goal of 79 %. The primary effectiveness end-point was the induced VF conversion rate compared with a pre-specified performance goal of 88 %, with success defined as 2 consecutive VF conversions of 4 attempts. Detection and conversion of spontaneous episodes were also evaluated. Device implantation was attempted in 321 of 330 enrolled patients, and 314 patients underwent successful implantation. The cohort was followed for a mean duration of 11 months. The study population was 74 % male with a mean age of 52 ± 16 years and mean LVEF of 36 ± 16 %. A previous transvenous ICD (TV-ICD) had been implanted in 13 %. Both primary end-points were met: The 180-day system complication-free rate was 99 %, and sensitivity analysis of the acute VF conversion rate was greater than 90 % in the entire cohort. There were 38 discrete spontaneous episodes of VT/VF recorded in 21 patients (6.7 %), all of which successfully converted. Forty-one patients (13.1 %) received an inappropriate shock. The authors concluded that the findings of this study supported the safety and effectiveness of the S-ICD System for the treatment of life-threatening ventricular arrhythmias. The main drawbacks of this study were the lack of a control group and the short duration of the follow-up.
In an accompanying editorial of the afore-mentioned study, Saxon noted that “Over the follow-up interval reported in this study, the subcutaneous ICD terminated spontaneously occurring VT/VF in 6.5 % of the patients implanted (21 patients). There were a total of 22 episodes of spontaneously occurring monomorphic VT and 16 episodes of VF treated. First and second shock success rate was 92 % and 97 %, respectively. Two patients had multiple successful shocks for VT storm. Although these data are reassuring and comparable to TV-ICD success rates, the overall number of treated episodes is incredibly small in comparison with the data on transvenous defibrillator therapies delivered outside the hospital, over the life of the device, that are available for analysis in tens of thousands of patients. Without the ability to remotely collect episodes in all subcutaneous device recipients, it is difficult to know how the learning around spontaneous VT/VF episodes and treatment will occur, other than the old-fashioned way, through case reports and post-approval registries. This is a significant limitation from a clinical learning and safety advisory perspective …. Without remote monitoring capability, it will be difficult to track the occurrences of these episodes in the population of patients who receive the subcutaneous ICD. This is concerning, because the population enrolled in the subcutaneous ICD study were 10 to 20 years younger than the standard transvenous ICD recipient. The age of the subcutaneous ICD recipients indicates that they may be a more active and more prone to over-sensing owing to subcutaneous sensing challenges or T-wave double counting …. Although the subcutaneous ICD is de-featured and exists only to defibrillate, it does represent a major engineering feat for an entirely subcutaneous system. Yet, the most profound technology advances in the past decades, particularly in the case of devices, allow for an enhancement of capability (and complexity) to the backend architecture and a simplification of design features and user interface. The subcutaneous ICD does not encompass these features nearly as much as the transvenous device. In the best of all possible worlds, the subcutaneous ICD will grow and evolve into a device whose design supports the growth of features and capabilities that can evolve with the patient’s condition. This includes integrating wirelessly with other hardware- and software-based healthcare solutions that will enhance the device and the device recipient's overall medical condition. The enhancements will provide multiple reasons for subcutaneous ICD to exist”.
Akerstrom et al (2013) stated that the S-ICD has recently been approved for commercial use in Europe, New Zealand and the United States. It is comprised of a pulse generator, placed subcutaneously in a left lateral position, and a parasternal subcutaneous lead-electrode with 2 sensing electrodes separated by a shocking coil. Being an entirely subcutaneous system it avoids important peri-procedural and long-term complications associated with transvenous implantable cardioverter-defibrillator (TV-ICD) systems as well as the need for fluoroscopy during implant surgery. Suitable candidates include pediatric patients with congenital heart disease that limits intra-cavitary lead placements, those with obstructed venous access, chronic indwelling catheters or high infection risk, as well as young patients with electrical heart disease (e.g., Brugada Syndrome, long QT syndrome, and hypertrophic cardiomyopathy). Nevertheless, given the absence of intra-cavitary leads, the S-ICD is unable to offer pacing (apart from short-term post-shock pacing). It is therefore not suitable in patients with an indication for anti-bradycardia pacing or cardiac resynchronization therapy, or with a history of repetitive monomorphic VT that would benefit from anti-tachycardia pacing. Current data from initial clinical studies and post-commercialization "real-life" case series, including over 700 patients, have so far been promising and shown that the S-ICD successfully converts induced and spontaneous VT/VF episodes with associated complication and inappropriate shock rates similar to that of TV-ICDs. Furthermore, by using far-field electrograms better tachyarrhythmia discrimination when compared to TV-ICDs has been reported. The authors concluded that future results from ongoing clinical studies will determine the S-ICD system's long-term performance, and better define suitable patient profiles.
Pettit et al (2013) compared the performance of S-ICD and TV-ICD systems in children and teenagers. These researchers studied consecutive patients less than 20 years of age who received an ICD over a 4-year period in 2 Scottish centers. Baseline characteristics, complications, and ICD therapy were recorded. The primary outcome measure was survival. The secondary outcome measure was survival-free from inappropriate ICD therapy or system revision. A total of 9 S-ICD were implanted in 9 patients; 8 TV-ICD were implanted in 6 patients; 2 were redo procedures. Baseline characteristics were well-matched. Median duration of follow-up was lower for S-ICD (20 months) than for TV-CD (36 months, p = 0.0262). Survival was 100 % in both groups. Survival free of inappropriate therapy or system revision was 89 % for S-ICD and 25 % for TV-ICD systems (log-rank test, p = 0.0237). No S-ICD were extracted, but 3 TV- ICD were extracted due to infection (n = 1) and lead failure (n = 2). The authors concluded that in real-world use in children and teenagers, S-ICD may offer similar survival benefit to TV-CD, with a lower incidence of complications requiring reoperation. They stated that in the absence of randomized trials, S-ICD should be compared prospectively with TV-ICD in large multi-center registries with comparable periods of follow-up.
Majithia et al (2014) noted that randomized clinical trials support the use of implantable defibrillators for mortality reduction in specific populations at high-risk for sudden cardiac death. Conventional transvenous defibrillator systems are limited by implantation-associated complications, infection, and lead failure, which may lead to delivery of inappropriate shocks and diminish survival. The development of a fully subcutaneous defibrillator may represent a valuable addition to therapies targeted at sudden death prevention. The PubMed database was searched to identify all clinical reports of the subcutaneous defibrillator from 2000 to the present. These investigators reviewed all case series, cohort analyses, and randomized trials evaluating the safety and effectiveness of subcutaneous defibrillators. The subcutaneous defibrillator is a feasible development in sudden cardiac death therapy and may be useful particularly to extend defibrillator therapy to patients with complicated anatomy, limited vascular access, and congenital disease. The subcutaneous defibrillator should not be considered in patients with an indication for cardiac pacing or who have VT responsive to anti-tachycardia pacing. The authors concluded that further investigation is needed to compare long-term, head-to-head performance of subcutaneous defibrillators and conventional transvenous defibrillator systems.
Furthermore, the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines on “The management of ST-elevation myocardial infarction” (O’Gara et al, 2013) mentioned ICD therapy; but not subcutaneous ICD.
On February 15, 2018, the Centers for Medicare & Medicaid Services (CMS) decison memo for ICDs made minimal changes to the ICD NCD to (i) require patients who have severe non-ischemic dilated cardiomyopathy but no personal history of sustained ventricular tachyarrhythmia or cardiac arrest due to ventricular fibrillation to have been on optimal medical therapy (OMT) for at least 3 months, and (ii) require a patient shared decision making (SDM) interaction prior to ICD implantation for certain patients. CMS guidelines for ICD in severe ischemic dilated cardiomyopathy include that patients must not have had a CABG, or PCI with angioplasty and/or stenting, within the past 3 months, had an MI within the past 40 days, or clinical symptoms and findings that would make them a candidate for coronary revascularization.
The 2017 AHA/ACC/HRS Guideline for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death includes recommendation for ICD as primary prevention of SCD in patients with ischemic heart disease with LVEF of 35% or less and who are at least 40 days’ post-MI, at least 90 days postrevascularization, NYHA class II or III HF despite GDMT, and meaningful survival greater than 1 year is expected. (LOE: A). In patients with LVEF of 30% or less that is due to ischemic heart disease who are at least 40 days’ post-MI and at least 90 days postrevascularization, and with NYHA class I HF despite guideline-directed management and therapy (GDMT), an ICD is recommended if meaningful survival of greater than 1 year is expected.
Previous Endocarditis or Device Infection as an Indication for Subcutaneous Defibrillator
De Maria et al (2014) stated the following regarding implanted and subcutaneous defibrillator: http://www.escardio.org/communities/councils/ccp/e-journal/volume12/Pages/subcutaneous-defibrillator-who-may-benefit-demaria-olaru-cappeli.aspx.
- Implantable cardioverter-defibrillator: Insertion of the electrode into the central venous circulation and inside cardiac chambers can cause vascular obstruction, thrombosis, infection and cardiac perforation. Moreover, lead failure has been estimated at 0.58 %/year and up to 20 % at 10 years; failures may require the leads to be extracted, however this is a highly challenging procedure: major complications rates are about 1 % and mortality is at 0.3 %, even in experienced centers.
- Subcutaneous defibrillator: The risk of systemic infections appears to be very low, best in high-risk cases of previous device infection, hemodialysis, chronic immunosuppression therapy immunodeficiencies, or artificial heart valves.
Subcutaneous defibrillator as first choice -- Previous endocarditis or device infection
Also, an UpToDate review on “Subcutaneous implantable cardioverter defibrillators” (Weinstock et al, 2015) states that “ICD systems consist of a pulse generator, typically placed in the pectoral region, and one or more leads which attach the pulse generator to the heart, most commonly to the endocardium via transvenous insertion. However, conventional transvenous ICD (TV-ICD) systems come with the inherent drawbacks of transvenous leads, including:
- Risks at the time of insertion -- Cardiac perforation, pericardial effusion, cardiac tamponade, hemothorax, pneumothorax
- Delayed risks over the lifetime of the device -- Intravascular lead infection, lead failure
Reports of complications at the time of TV-ICD range from 3 to 6 % of implants. In addition, the delayed risks of transvenous leads include a risk of infection (incidence of 9 per 1,000 device-years) and lead failure (ranging from 5 to 40 %of leads at 5 years depending on the type of lead), both of which lead to repeat procedures and increased morbidity for patients …. The subcutaneous implantable cardioverter defibrillator (S-ICD) system obviates some of the mechanical complications associated with transvenous lead implantation (e.g., cardiac perforation leading to pericardial effusion and cardiac tamponade, hemothorax, pneumothorax, endovascular lead infection)”.
Defibrillation Threshold (DFT) Testing During Implantable Cardioverter-Defibrillator Implantation
Gula et al (2008) noted that defibrillation threshold (DFT) testing is generally performed during implantation of ICDs to assess sensing and termination of VF. It is common clinical practice to defibrillate VF twice at an output at least 10 J below the maximum output of the device, providing a 10 J safety margin. However, there are few data regarding impact of DFT testing on outcomes. These investigators evaluated the impact of DFT testing of implanted ICDs on survival. Decision analysis and Monte Carlo simulation were used to assess expected outcomes of DFT testing. Survival of a hypothetical cohort of patients was assessed according to 2 strategies-routine DFT testing at time of ICD implant versus no DFT testing. Assumptions in the model were varied over a range of reasonable values to assess outcomes under a variety of scenarios. Five-year survival rates with DFT and no-DFT strategies were similar at 59.72 % and 59.36 %, respectively. The results were not sensitive to changing risk estimates for arrhythmia incidence and safety margin. Results of the Monte Carlo simulation were qualitatively similar to the base case scenario and consistent with a small and non-significant survival advantage with routine DFT testing. The authors concluded that the impact of DFT testing on 5-year survival in ICD patients, if it exists, is small. Survival appears higher with DFT testing as long as annual risk of lethal arrhythmia or the risk of a narrow safety margin is at least 5 %, although the incremental benefit is marginal and 95 % CIs cross zero. They stated that a prospective randomized study of DFT testing in modern devices is warranted.
Bianchi et al (2009) compared the outcome of ICD recipients who underwent DFT testing with that of patients in whom no testing was performed. A total of 291 subjects with ischemic dilated cardiomyopathy received transvenous ICDs between January 2000 and December 2004 in 5 Italian cardiology centers were included in this study. In 2 centers, DFT testing was routinely performed in 137 patients (81 % men; mean age of 69 +/- 9 years; mean ejection fraction of 26 +/- 4 %) (DFT group), while 3 centers never performed DFT testing in 154 patients (90 % men; mean age of 69 +/- 9 years; mean ejection fraction of 27 +/- 5 %) (no-DFT group). These researchers compared total mortality, total cardiovascular mortality, SCD, and spontaneous episodes of ventricular arrhythmia (sustained ventricular tachycardia, VT, and ventricular fibrillation, VF) between these groups 2 years after implantation (median of 23 months; 25th to 75th percentile; 12 to 44 months). On comparing the DFT and no-DFT groups, these investigators found an overall mortality rate of 20 % versus 16 %, cardiovascular mortality of 13 % versus 10 %, SCD of 3 % versus 0.6 %, VT incidence of 8 % versus 10 %, and VF incidence of 6 % versus 4 % (no significant difference in any comparison). The authors concluded that no significant differences in the incidence of clinical outcomes considered emerged between no-DFT and DFT groups. They stated that these results should be confirmed in larger prospective studies.
Stefano et al (2011) stated that clinical practice with regard to DFT testing during ICD implantation varies considerably, even among experienced implanting centers. International guidelines do not as yet mandate DFT testing. These investigators evaluated current clinical decision making regarding DFT testing during ICD implantation. The ALIVE project collected data on DFT testing from a multi-center network of Italian clinicians sharing a common system for the collection, management, analysis, and reporting of clinical and diagnostic data from patients with Medtronic (Minneapolis, MN) implantable devices. Data on 2,082 consecutive patients implanted with a Medtronic ICD in 111 Italian centers, over the period 2007 to 2010, were analyzed. Defibrillation threshold testing was performed in 33 % of cases (678/2,082). The main reasons for performing the test were physician's clinical practice ("I always perform DFT") (80 %) and secondary prevention implantation (12 %). The main reasons for not performing DFT testing were centers' practice (44 %), primary prevention (31 %), and device replacement (15 %). In 22 patients, VF induction was not achieved; 656 patients completed DFT testing: 633 patients (96 %) performed a single test, 19 patients (3 %) performed a second induction test, and 4 patients (0.6 %) underwent an additional induction test. The authors concluded that the preliminary results of the ALIVE project showed that a great number of implant procedures were performed without DFT testing in the common practice of the participating centers. They also measured an inhomogeneous, center-dependent DFT testing behavior, which suggested the importance of defining a common guideline for ICD implant testing. They stated that follow-up data on these patients will provide more information on the clinical value of the test.
Russo and Chung (2014) noted that with advancements in ICD technology, the practice of performing DFT testing at the time of implantation has been questioned. With availability of biphasic waveforms, active cans, and high-output devices, opponents claim that DFT testing is no longer necessary. Clinical trials demonstrating the effectiveness of ICDs in prevention of SCD have, however, all used some form of defibrillation testing. This debate is fueled by the absence of data from randomized prospective trials evaluating the role of DFT testing in predicting clinical shock efficacy or survival.
In a single-blind, randomised, multi-center, non-inferiority clinical trial (Shockless IMPLant Evaluation [SIMPLE]), Healey et al (2015) compared the safety and effectiveness of ICD implantation without DFT testing versus the standard of ICD implantation with DFT testing. These investigators recruited patients aged older than 18 years receiving their first ICD for standard indications at 85 hospitals in 18 countries worldwide. Exclusion criteria included pregnancy, awaiting transplantation, participation in another randomised trial, unavailability for follow-up, or if it was expected that the ICD would have to be implanted on the right-hand side of the chest. Patients undergoing initial implantation of a Boston Scientific ICD were randomly assigned (1:1) using a computer-generated sequence to have either DFT (testing group) or not (no-testing group). These researchers used random block sizes to conceal treatment allocation from the patients, and randomization was stratified by clinical center. The primary efficacy analysis tested the intention-to-treat population for non-inferiority of no-testing versus testing by use of a composite outcome of arrhythmic death or failed appropriate shock (i.e., a shock that did not terminate a spontaneous episode of ventricular tachycardia or fibrillation). The non-inferiority margin was a hazard ratio (HR) of 1.5 calculated from a proportional hazards model with no-testing versus testing as the only covariate; if the upper bound of the 95 % CI was less than 1.5. These investigators concluded that ICD insertion without testing was non-inferior to ICD with testing. They examined safety with 2, 30-day, adverse event outcome clusters. Between January 13, 2009 and April 4, 2011, of 2,500 eligible patients, 1,253 were randomly assigned to defibrillation testing and 1,247 to no-testing, and followed-up for a mean of 3.1 years (SD 1.0). The primary outcome of arrhythmic death or failed appropriate shock occurred in fewer patients (90 [7 % per year]) in the no-testing group than patients who did receive it (104 [8 % per year]; HR 0.86, 95 % CI: 0.65 to 1.14; p (non-inferiority) < 0.0001). The first safety composite outcome occurred in 69 (5.6 %) of 1,236 patients with no-testing and in 81 (6.5 %) of 1,242 patients with defibrillation testing, p = 0·33. The second, pre-specified safety composite outcome, which included only events most likely to be directly caused by testing, occurred in 3.2 % of patients with no-testing and in 4.5 % with defibrillation testing, p = 0·08. Heart failure needing intravenous treatment with inotropes or diuretics was the most common adverse event (in 20 [2 %] of 1,236 patients in the no-testing group versus 28 [2 %] of 1,242 patients in the testing group, p = 0·25). The authors concluded that routine defibrillation testing at the time of ICD implantation is generally well-tolerated, but does not improve shock efficacy or reduce arrhythmic death.
Implantable Cardioverter-Defibrillator Use in Patients With Left Ventricular Assist Devices
Enriquez and co-workers (2013) noted that the prognosis for patients experiencing ventricular arrhythmias (VAs) while on continuous flow LVAD support has not been well elucidated. Accordingly, the role of ICDs in this patient population remains undefined. Records of 106 consecutive patients undergoing implantation of the HeartMate II LVAD at a single center were reviewed. For patients surviving greater than 30 days post-implant (98 patients), the impact of VAs and ICDs on survival was analyzed. Mean age was 56.6 ± 11.4 years, 82.1 % were male, 42.5 % had an ischemic cardiomyopathy, 87.7 % were bridge to transplantation (BT), and median length of support was 217 days. A total of 21 (19.8 %) patients died, 60 (56.6 %) survived to transplantation, and 25 patients (23.6 %) reached the end of study, had the LVAD explanted, or were lost to follow-up. Post-LVAD VAs occurred in 37 patients (34.9 %); but were not associated with increased mortality (HR, 0.58 [0.18 to 1.90]); 62 (63.3 %) patients had an active ICD, and 36 (36.7 %) patients had no ICD or an inactivated ICD post-LVAD. Patients with an ICD were more likely to be INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) level 3 or 4 at the time of implant (54.8 % versus 33.3 %; p = 0.04). An appropriate shock was delivered in 27.3 % of patients, but the presence of an active ICD was not associated with improved survival (HR, 1.12 [0.37 to 3.35]). The authors concluded that VAs were common in patients with continuous flow LVADs. Although some episodes may be clinically significant, VAs were not associated with a worse prognosis, and concomitant ICDs in these patients may not reduce mortality.
In a systematic review and meta-analysis, Vakil and colleagues (2016) evaluated the impact of ICDs on mortality in patients with left ventricular assist devices (LVADs). Relevant studies from January 2000 through October 2015 were identified in the databases PubMed and OVID. Weighted relative risks were estimated using random effects meta-analysis techniques. A total of 6 observational studies (n = 937) were included. Patients were 53 ± 12 years of age, and 80 % were male; BT was the indication for LVAD use in 93 % of the patients. A continuous-flow (CF) LVAD was present in 39 % of patients. Mean LVEF was 16 ± 6 %. An ICD was present in 355 patients (38 %). During a mean follow-up of 7 months, 241 patients (26 %) died (16 % in the ICD group versus 32 % in the no-ICD group). Presence of an ICD was associated with a 39 % relative risk reduction in all-cause mortality (relative risk [RR]: 0.61; 95 % CI: 0.46 to 0.82; p < 0.01). Among subgroup of patients with CF-LVAD (n = 361), ICD use was associated with a statistically non-significant trend toward improved survival (RR: 0.76; 95 % CI: 0.51 to 1.12; p = 0.17). The authors concluded that ICD use was associated with a significant reduction in mortality in LVAD patients, however, this effect was not significant in patients with CF-LVADs. They stated that although these data support the use of ICDs, larger randomized trial data are strongly needed to evaluate ICD effectiveness in patients with current generation LVADs.
Agrawal and associates (2016) evaluated the impact of presence of ICD on mortality in continuous flow LVAD recipients. A meta- analysis of available literature was performed. PubMed, Embase and Google Scholar databases were searched for studies that compared mortality in continuous flow LVAD patients with ICDs (new implantation or no de-activation) and without ICDs (including de-activation of existing implant). Pooled analysis using a fixed effects model was used for outcomes of interest. These investigators included 3 observational studies for a total of 292 patients (203 (69.5 %) with ICD versus 89 (30.5 %) without ICD). The presence of an active ICD was not associated with improved survival [odds ratio [OR] 0.63, 95 % CI: 0.33 to 1.18; p = 0.15]. In BT patients (224 patients, 149 with ICD versus 75 without ICD), an active ICD was not associated with a higher probability of survival [OR 1.47, 95 % CI: 0.78 to 2.76; p = 0.23]. There was no difference in the occurrence of severe right ventricular dysfunction or failure between 2 groups [OR 0.78, 95 % CI: 0.42 to 1.47; p = 0.45]. The risk of LVAD related complications were similar [OR 0.68, 95 % CI: 0.35 to 1.31; p = 0.25]. The authors concluded that this meta-analysis demonstrated that there is no survival benefit with ICD in heart failure patients supported with continuous flow LVAD. They stated that there is an urgent need of large-scale randomized trials to specifically address this issue.
Transvenous Versus Subcutaneous Implantable Cardioverter-Defibrillator Therapy
Su et al (2021) stated that the use of TV-ICDs is associated with multiple risks related to the presence of the defibrillator leads within the venous system and right side of the heart, including endocarditis, venous occlusion, tricuspid regurgitation, and potential lead failure. The emergence of S-ICDs may potentially overcome the afore-mentioned disadvantages. However, evidence validating the safety of S-ICDs relative to TV-ICDs is limited. These investigators examined available data from published studies to compare TV-ICD and S-CDs. Different databases were searched for full-text publications with a direct comparison of TV-ICDs and S-ICDs. Fixed effect models were applied to pooled data, and no study-to-study heterogeneity was detected. Data from 7 studies totaling 1,666 patients were pooled together. Compared to S-ICDs, the risk of suffering device-related complications was higher in patients with TV-ICDs (OR = 1.71; 95 % CI: 1.23 to 2.38). The number of patients with an S-ICD who suffered inappropriate shocks (IS) was not significantly different than patients with a TV-ICD (OR = 0.92; 95 % CI: 0.65 to 1.30). Subgroup analysis indicated that the TV-ICD group had a higher risk of IS due to supra-ventricular over-sensing (OR = 3.29; 95 % CI: 1.92 to 5.63) while T-wave over-sensing tending to cause IS in the S-ICD group (OR = 0.09; 95 % CI: 0.03 to 0.23). The risk of device-related infection in the S-ICD group was not any lower than that in the TV-ICD group (OR = 1.57; 95 % CI: 0.67 to 3.68). The survival rate without any complications during a 1-year follow-up period was similar between the 2 groups (HR = 1.23; 95 % CI: 0.81 to 1.86), although it was assumed that the trend leaned toward more complications in patients with a TV-ICD. The authors concluded that the findings of this study verified the safety of S-ICDs based on pooled data. Although there were no differences between TV- and S-ICDs in the short-term, fewer adverse events (AEs) were found in patients with S-ICDs during long-term follow-up.
Nso et al (2022) noted that S-ICD and TV-ICD devices effectively reduce the incidence of SCD in patients at a high risk of VAs . These researchers examined the safe replacement of TV-ICD with S-ICD based on updated recent evidence. They systematically searched Embase, JSTOR, PubMed/Medline, and Cochrane Library on July 30, 2021 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. These researchers identified 26 studies that examined 7,542 (58.27 %) patients with S-ICD and 5,400 (41.72 %) with TV-ICD. The findings indicated that, compared to patients with TV-ICD, patients with S-ICD had a lower incidence of defibrillation lead failure (OR, 0.12; 95 % CI: 0.01 to 0.98; p = 0.05), lead displacement or fracture (OR, 0.25; 95 % CI: 0.12 to 0.86; p = 0.0003), pneumothorax and/or hemothorax (OR: 0.22, 95 % CI: 0.05 to 0.97, p = 0.05), device failure (OR: 0.70, 95 % CI: 0.51 to 0.95, p = 0.02), all-cause mortality (OR: 0.44, 95 % CI: 0.32 to 0.60, p < 0.001), and lead erosion (OR: 0.01, 95 % CI: 0.00 to 0.05, p < 0.001). Patients with TV-ICD had a higher incidence of pocket complications than patients with S-ICD (OR, 2.13; 95 % CI: 1.23 to 3.69; p = 0.007) and a higher but insignificant incidence of inappropriate sensing (OR, 3.53; 95 % CI: 0.97 to 12.86; p = 0.06). The authors concluded that S-ICD algorithm was safer and more effective than the TV-ICD system as it minimized the incidence of pocket complications, lead displacement or fracture, inappropriate sensing, defibrillation lead failure, pneumothorax/hemothorax, device failure, lead erosion, and all-cause mortality. Moreover, these researchers stated that future studies should examine the scope of integrating novel algorithms with the current S-ICD systems to improve cardiovascular outcomes.
N-Terminal Pro-B-Type Natriuretic Peptide in Risk Stratification of Heart Failure Patients with Implantable Cardioverter-Defibrillator
Deng et al (2022) stated that the prognostic value of N-terminal pro-B-type natriuretic peptide (NT-proBNP) in heart failure (HF) is well-established; however, whether it could facilitate the risk stratification of HF patients with ICD is still unclear. These researchers examined the associations between baseline NT-proBNP and outcomes of all-cause mortality and 1st appropriate shock due to sustained ventricular tachycardia/ventricular fibrillation (VT/VF) in ICD recipients. NT-proBNP was measured before ICD implant in 500 patients (mean age of 60.2 ± 12.0 years; 415 (83.0 %) men; 231 (46.2 %) non-ischemic dilated cardiomyopathy (DCM); 136 (27.2 %) primary prevention). The median NT-proBNP was 854.3 pg/ml (inter-quartile range [IQR]: 402.0 to 1,817.8 pg/ml). These investigators categorized NT-proBNP levels into quartiles and used a restricted cubic spline to examine its non-linear association with outcomes. The incidence rates of mortality and 1st appropriate shock were 5.6 % and 9.1 %, respectively. After adjusting for confounding factors, multi-variable Cox regression showed a rise in NT-proBNP was associated with an increased risk of all-cause mortality. Compared with the lowest quartile, the HRs with 95 % CI across increasing quartiles were 1.77 (0.71 to 4.43), 3.98 (1.71 to 9.25), and 5.90 (2.43 to 14.30) for NT-proBNP (p for trend < 0.001). A restricted cubic spline showed a similar pattern with an inflection point found at 3,231.4 pg/ml, beyond which the increase in NT-proBNP was not associated with increased mortality (p for non-linearity < 0.001). Fine-Gray regression was used to examine the association between NT-proBNP and 1st appropriate shock accounting for the competing risk of death. In the unadjusted, partial, and fully adjusted analysis, however, no significant association could be found regardless of NT-proBNP as a categorical variable or log-transformed continuous variable (all p > 0.05). No non-linearity was found, either (p = 0.666). Interactions between NT-proBNP and pre-defined factors were not found (all p > 0.1). The authors concluded that increasing NT-proBNP levels were related to an increased risk of death with a ceiling effect at 3,231.4 pg/ml, but not related to the 1st appropriate shock; thus, patients with higher NT-proBNP might derive less benefit from ICD implant. Moreover, these researchers stated that further investigation is needed to confirm these findings.
The authors stated that this study had several drawbacks. First, the mean follow-up duration of shock status was less than that of survival status. It might undermine the power of this analysis. However, it was comparable with other studies dedicated to solving this hypothesis. Moreover, the follow-up period did not have an influence on the HR in the proportional hazards model in the absence of time-varying variables. Second, these researchers only examined the baseline effect of NT-proBNP instead of repetitive levels. Dynamic changes in NT-proBNP levels and echocardiography parameters might provide incremental information on prognosis. For example, an improvement in LVEF was associated with reduced ICD therapy and lower mortality. However, due to the retrospective nature of this trial, it was hard to strictly choose unified time-points to define serial change. Nonetheless, this trial showed that a single baseline NT-proBNP level was a predictor of death, which is easier to interpret and use in clinical setting. Third, the endpoint did not include anti-tachycardic pacing, which might also be triggered by fatal arrhythmic events. In fact, the inclusion of anti-tachycardic pacing is not proper because it was mainly designed for treating hemodynamically stable, slower rate ventricular tachyarrhythmia. As a result, only appropriate shock was included as the endpoint.
Prameswari et al (2023) noted that several studies have reported that combining LVEF and NYHA functional class is insufficient for predicting risk of appropriate ICD shock in primary prevention candidates. In a systematic review and meta-analysis, these investigators examined the relationship between NT-pro BNP along with appropriate ICD shock and all-cause mortality to improve the stratification process of patients with heart failure with reduced ejection fraction (HFrEF) being considered for primary preventive ICD therapy. They carried out a systematic literature search from several databases up until June 9, 2022. Studies were eligible if they examined the relationship of NT-pro BNP with all-cause mortality and appropriate ICD shock. This meta-analysis comprised 9 studies with a total of 5,117 subjects. This study showed that high levels of NT-pro BNP were associated with all-cause mortality (HR = 2.12 (95 % CI: 1.53 to 2.93); p < 0.001, I2 = 78.1 %, p < 0.001 for heterogeneity) and appropriate ICD shock (HR = 1.71 (95 % CI: 1.18 to 2.49); p < 0.001, I2 = 43.4 %, p = 0.102 for heterogeneity). The adjusted HR for all-cause mortality and appropriate ICD shock increased by approximately 3 % and 5 %, respectively per 100 pg/ml increment pursuant to concentration-response model (P non-linearity < 0.001). The curves became steeper after NT-pro BNP reached its inflection point (3,000 pg/ml). The authors concluded that a positive concentration-dependent association between elevated NT-pro BNP levels along with the risk of all-cause mortality and appropriate ICD shock was found in patients with HFrEF with ICD. These researchers proposed that NT-pro BNP should be included into future studies as a factor that may be helpful in diagnosing those who might benefit from ICD therapy. They stated that more cohort studies examining the predictive value of NT-pro BNP in ischemic cardiomyopathy (ICM) and non-ischemic cardiomyopathy (NICM) separately are needed to increase the use of NT-pro BNP as a prognosticator of poorer outcomes in patients with HFrEF who underwent ICD implantation as the main prevention for SCD.
The authors stated that this meta-analysis had several drawbacks. First, 4 of the 9 included studies were retrospective cohorts; thus, it increased the likelihood of recall and selection bias. Second, several confounding factors that altered NT-pro BNP levels were not entirely excluded by all included studies; therefore, increasing the possibility of bias. Third, the dynamic variations in NT-pro BNP caused by several afore-mentioned factors, which represented the variability of ventricular dilatation degree, might increase the risk of ventricular arrhythmic events over time. However, this analysis was confined to examining the prognostic value of baseline NT-pro BNP. As a result, it may over-estimate or under-estimate the likelihood of the outcomes of interest. Finally, several observational studies that studied the connection between NT-pro BNP along with all-cause mortality and appropriate ICD shock in patients with ICM and NICM separately were utmost important in light of this debatable subject regarding the indication of primary preventive ICD treatment in NICM population.
Appendix
New York Heart Association Functional Classification of Cardiac Disability
Class I: Patients with cardiac disease but without resulting limitations of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea, or anginal pain.
Class II: Patients with cardiac disease resulting in slight limitation of physical activity. They are comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea, or anginal pain.
Class III: Patients with cardiac disease resulting in marked limitation of physical activity. They are comfortable at rest. Less than ordinary physical activity causes fatigue, palpitation, dyspnea, or anginal pain.
Class IV: Patients with cardiac disease resulting in inability to carry on any physical activity without discomfort. Symptoms of cardiac insufficiency or of the anginal syndrome may be present even at rest. If any physical activity is undertaken, discomfort is increased.
Source: Adapted from Goldman et al (1981).
References
The above policy is based on the following references:
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