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Clinical Policy Bulletin:
T-Wave Alternans
Number: 0579


Policy

Aetna considers microvolt T-wave alternans (MTWA) diagnostic testing using the spectral analytic method medically necessary for the evaluation of persons at risk of sudden cardiac death who meet criteria for implantable cardioverter-defibrillator placement.  

Aetna considers MTWA diagnostic testing using the spectral analytic method experimental and investigational for all other indications because of insufficient evidence in the peer-reviewed literature (e.g., diagnosis and risk assessment of acute coronary syndrome, guiding anti-arrhythmic therapy, and judging the severity of ischemic cardiomyopathy).

See  CPB 0585 - Cardioverter-Defibrillators.



Background

The term alternans applies to conditions characterized by the sudden appearance of a periodic beat-to-beat change in some aspect of cardiac electrical or mechanical behavior.  Many different examples of electrical alternans have been described clinically; a number of others have been reported in the laboratory. 

T-wave alternans has long been recognized as a marker of electrical instability in acute ischemia, where it may precede ventricular tachyarrhythmia.  Studies have shown that T wave (or ST-T) alternans can also precede non-ischemic ventricular tachyarrhythmias.  Considerable interest has recently been shown in the detection of microvolt T wave alternans as a noninvasive marker of the risk of ventricular tachyarrhythmia in patients with chronic heart disease.

Assessment of left ventricular ejection fraction (LVEF), Holter monitoring, and signal-averaged late potentials are the principal non-invasive means of determining the risk of ventricular arrhythmias after myocardial infarction (MI).  However, these measures of vulnerability to arrhythmias have been found to be less predictive of arrhythmic events than invasive electrophysiologic testing.

Microvolt T-wave alternans testing is performed by placing high-resolution electrodes, designed to reduce electrical interference, on a patient’s chest prior to a period of controlled exercise (CMS, 2005).  These electrodes detect tiny beat-to-beat changes, on the order of one-millionth of volt, in the EKG T-wave.  Spectral analysis is used to calculate these minute voltage changes.  Spectral analysis is a sensitive mathematical method of measuring and comparing time and the electrocardiogram signals.  Software then analyzes these microvolt changes and produces a report to be interpreted by a physician.

T-wave alternans has primarily been used for defining the risk of ventricular arrhythmias in persons at risk for sudden cardiac death and determining which patients are most likely to benefit from implantable cardioverter-defibrillators.  Cambridge Heart, Inc. (Fort Lauderdale, FL) Cardiac Diagnostic System Model CH 2000, which measures T-wave alternans at rest and with exercise, was cleared by the Food and Drug Administration (FDA) based on an 510(k) application.

A decision memorandum from the Centers for Medicare and Medicaid Services (CMS, 2006) found that the quality of evidence is adequate to conclude that microvolt T-wave alternans testing using a spectral analysis algorithm can improve net health outcomes, and is reasonable and necessary for Medicare patients who are candidates for ICD placement.  The decision memorandum explained that the reviewed literature contains a number of studies evaluating the use of microvolt T-wave alternans (MTWA) in a variety of population settings, including subjects with congestive heart failure (CHF), ischemic CHF, non-ischemic CHF, dilated cardiomyopathy, hypertrophic cardiomyopathy, post-MI, and in healthy subjects.  The decision memorandum noted that the material reviewed included not only small prospective studies with a homogenous patient population, but also large systematic reviews with heterogeneous patient populations.  Also included in the CMS analysis were studies that looked specifically at MTWA's role as a risk stratification tool in patient populations similar to those in pivotal clinical studies of implantable cardioverter-defibrillators.

The decision memorandum noted that most of the studies used in CMS’ assessment of MTWA included measures of diagnostic accuracy (e.g., sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) (CMS, 2006).  CMS found that, when reviewing these measures of accuracy, MTWA testing demonstrated superior findings related to sensitivity and NPV when compared to other diagnostic tests used to assess risk of ventricular tachyarrhythmias.

The CMS decision memorandum stated that “[a]cross a number of population settings, MTWA [microvolt T-wave alternans] consistently demonstrates superiority when compared to other diagnostic measures that assess risk of VTEs [ventricular tachyarrhythmic events].  Though some of the studies noted some limitations related to methodology as well as research design, these limitations were not enough to invalidate their findings” (CMS, 2006).

The CMS decision memorandum commented on a technology assessment of MTWA published by the BlueCross BlueShield Association (BCBSA) Technology Evaluation Center (TEC).  The TEC assessment concluded that that “[t]he available evidence on MTWA is insufficient to permit conclusions regarding the effect on health outcomes.”  Regarding use of MTWA in evaluating subjects eligible for placement of an implantable cardioverter defibrillator given current patient selection criteria, the TEC assessment stated that the available evidence is limited (BCBSA, 2005). 

The CMS decision memorandum explained that differences in the conclusions of the TEC assessment and CMS analysis are due, in part, to the unique characteristics of the Medicare-eligible population (i.e. elderly, and more likely to have multiple co-morbidities) (CMS, 2006).  The decision memorandum explained that sudden cardiac death has a higher potential to occur as a result of ventricular tachyarrhythmias in this population.  The decision memorandum explained that potential harms from adverse events are also more likely to occur within this population.  The CMS decision memorandum stated that “[b]ecause of these features of the Medicare population, the potential for benefit or harm from ICD placement varies from that of the BCBSA population at large, and plays a prominent role in our decision making.”  The decision memorandum also noted that indications for ICD placement also differ between the 2 organizations.  “Because of the higher potential for VTE occurrence in the Medicare population, and because CMS recognizes VTEs as an indication for ICD placement, CMS feels that the use of MTWA is reasonable and necessary to address problems related to VTE and its adverse consequences.”

The CMS decision memorandum concluded that MTWA is a useful risk stratification tool and can identify which heart patients are at negligible risk of sudden death, and who may therefore be able to avoid implantable cardioverter defibrillator placement and its attendant risks (CMS, 2006).

The CMS decision memorandum states that MTWA testing is only covered when the spectral analytic method is used (CMS, 2006) because the evidence only supports the use of this algorithm for the detection of MTWA.  The decision memorandum explained that, although algorithms other than spectral analysis have been used to measure MTWA (e.g., modified moving average), CMS identified no peer-reviewed published articles discussing these other algorithms.

It has also been suggested that MTWA testing may be useful in determining the types and doses of medications (e.g., angiotensin converting enzyme inhibitors, beta-blockers, aldosterone antagonists) used to treat underlying cardiac conditions (e.g., left ventricular dysfunction, patients with recent MI) and to suppress arrhythmias.  However, there are no prospective clinical studies of the use of MTWA testing in adjusting pharmacotherapy.

Verrier and Nieminen (2010) stated that over 100 studies enrolling a total of more than 12,000 patients support the predictivity of TWA testing for cardiovascular mortality and sudden cardiac death during both exercise and ambulatory electrocardiogram monitoring.  To date, the main intended application has been to aid decision-making for cardioverter-defibrillator implantation.  The prospect that TWA could be used to guide pharmacologic therapy has not received adequate attention.  These investigators reviewed the literature supporting the utility of TWA as a therapeutic marker of anti-arrhythmic effects and pro-arrhythmia for each of the major anti-arrhythmic drug classes.  Beta-adrenergic and sodium channel blocking agents are the most widely studied drug classes in clinical TWA investigations, which report reductions in TWA magnitude.  Patients with Brugada syndrome constitute a significant exception, because sodium channel blockade provokes the diagnostic electrocardiogram changes as well as macroscopic TWA.  Calcium channel blockers have undergone extensive research in several animal models, but, surprisingly, no clinical studies on TWA with this class of drugs have been performed.  Interestingly, TWA may help to detect the beneficial effects of non-antiarrhythmic agents such as the angiotensin II receptor blocker valsartan, which exert their protective effects through putative indirect actions on myocardial remodeling.  There is also suggestive evidence that the pro-arrhythmic effects associated with cardiovascular and non-cardiovascular agents may be disclosed by elevated levels of TWA.  Thus, the emerging collective evidence indicates the broad utility of TWA in estimating anti-arrhythmic and pro-arrhythmic effects of diverse agents across differing pathologies.  The authors concluded that quantitative analysis of TWA has considerable potential to guide pharmacologic therapy.

Gold et al (2008) noted that sudden cardiac death remains a leading cause of mortality despite advances in medical treatment for the prevention of ischemic heart disease and heart failure.  Recent studies showed a benefit of implantable cardioverter-defibrillator implantation, but appropriate shocks for ventricular tachyarrhythmias were noted only in a minority of patients during 4 to 5 years of follow-up.  Accordingly, better risk stratification is needed to optimize patient selection.  In this regard, MTWA has emerged as a potentially useful measure of arrhythmia vulnerability, but it has not been evaluated previously in a prospective, randomized trial of implantable cardioverter-defibrillator therapy.  This investigation was a prospective substudy of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) that included 490 patients at 37 clinical sites.  Microvolt T-wave alternans tests were classified by blinded readers as positive (37 %), negative (22 %), or indeterminate (41 %) by standard criteria.  The composite primary end point was the first occurrence of any of the following events: (i) sudden cardiac death, (ii) sustained ventricular tachycardia/fibrillation, or (iii) appropriate implantable cardioverter-defibrillator discharge.  During a median follow-up of 30 months, no significant differences in event rates were found between MTWA-positive or MTWA-negative patients (hazard ratio 1.24, 95 % confidence interval [CI]: 0.60 to 2.59, p = 0.56) or MTWA-negative and non-negative (positive and indeterminate) subjects (hazard ratio 1.28, 95 % CI: 0.65 to 2.53, p = 0.46).  Similar results were obtained with the inclusion or exclusion of patients randomized to amiodarone in the analyses.  The authors concluded that MTWA testing did not predict arrhythmic events or mortality in SCD-HeFT, although a small reduction in events (20 % to 25 %) among MTWA-negative patients can not be excluded given the sample size of this study.  Accordingly, these results suggested that MTWA is not useful as an aid in clinical decision making on implantable cardioverter-defibrillator therapy among patients with heart failure and left ventricular systolic dysfunction.

Scirica (2010) stated that although there are many established tools for diagnosis, prognosis, and clinical decision making for acute coronary syndrome, understanding the advantages and limitations of each tool according the clinical scenario is essential.  Several emerging tools, such as novel biomarkers (e.g., high-sensitivity troponin and growth differential factor-15), ECG techniques (e.g., heart rate turbulence or TWA), and imaging modalities (computed tomography angiography and cardiac magnetic resonance) may potentially improve clinical care; however, they must be fully evaluated and validated in different scenarios and patient cohorts before they are incorporated into clinical practice.

On behalf of the International Society for Holter and Noninvasive Electrocardiology (and co-sponsored by the Japanese Circulation Society, the Computers in Cardiology Working Group on e-Cardiology of the European Society of Cardiology, and the European Cardiac Arrhythmia Society), Verrier et al (2011) prepared a consensus guideline on the electrocardiographic phenomenon of TWA.  This statement focused on its physiological basis and measurement technologies and its clinical utility in stratifying risk for life-threatening ventricular arrhythmias.  Signal processing techniques including the frequency-domain spectral method and the time-domain modified moving average method have demonstrated the utility of TWA in arrhythmia risk stratification in prospective studies in  more than 12,000 patients.  The majority of exercise-based studies using both methods have reported high relative risks for cardiovascular mortality and for sudden cardiac death in patients with preserved as well as depressed LVEF.  Studies with ambulatory electrocardiogram-based TWA analysis with modified moving average method have yielded significant predictive capacity.  However, negative studies with the spectral method have also appeared, including 2 interventional studies in patients with implantable defibrillators.  Meta-analyses have been performed to gain insights into this issue.  Frontiers of TWA research include use in arrhythmia risk stratification of individuals with preserved ejection fraction, improvements in predictivity with quantitative analysis, and utility in guiding medical as well as device-based therapy.  The authors concluded that although TWA appears to be a useful marker of risk for arrhythmic and cardiovascular death, there is as yet no definitive evidence from interventional trials that it can guide therapy. 

In a meta-analysis, Chen et al (2012) systematically reviewed current literature to determine the ability of MTWA to predict the outcome severity following ischemic cardiomyopathy (ICM).  Major endpoints include composite endpoint of cardiac mortality and severe arrhythmic events in primary prevention of patients with ICM, as well as all-cause mortality (cardiac death, and/or non-cardiac death).  A total of 7 trials were included by using MTWA for risk stratification of cardiac events in 3,385 patients with ICM. All patients were distributed into two groups according to the results of MTWA tests: non-negative group included positive and indeterminate, and negative group. Compared with the negative group, non-negative group showed increased rates of cardiac mortality or severe arrhythmic events (RR = 1.65, 95 % CI: 1.32 to 2.071), sudden cardiac death (SCD) (RR = 2.04 95 % CI: 1.11 to 3.75), and all-cause mortality (RR = 2.11, 95 % CI: 1.60 to 2.79).  The funnel plot revealed that there might be bias within current publications.  The fail-safe number of composite endpoint and all-cause mortality was 14.42 and 18.93, respectively (when p = 0.01).  The fail-safe number of SCD was 1.07 (when p = 0.05), which may be caused by the small case number of included studies and some patients with ICD included.  The authors concluded that the non-negative group of MTWA had a nearly double risk of severe outcomes compared with the negative group.  Therefore, MTWA represents a potential useful tool for judging the severity of ICM.

 
CPT Codes / HCPCS Codes / ICD-9 Codes
CPT codes covered if selection criteria are met:
93025
Other CPT codes related to the CPB:
93000 - 93010
93224
93225
93226
93278
93600 - 93662
ICD-9 codes covered if selection criteria are met:
425.11 - 425.18 Hypertrophic cardiomyopathy
425.4 Other primary cardiomyopathies
427.0 Paroxysmal supraventricular tachycardia [not covered guiding anti-arrhythmic therapy]
427.1 Paroxysmal ventricular tachycardia [not covered guiding anti-arrhythmic therapy]
427.2 Paroxysmal tachycardia, unspecified [not covered guiding anti-arrhythmic therapy]
427.41 Ventricular fibrillation [not covered guiding anti-arrhythmic therapy]
427.42 Ventricular flutter [not covered guiding anti-arrhythmic therapy]
427.5 Cardiac arrest [not covered guiding anti-arrhythmic therapy]
ICD-9 codes not covered for indications listed in the CPB (not all-inclusive)::
411.1 Intermediate Coronary Syndrome
427.31 - 427.32, 427.60 - 427.9 Cardiac dysrhythmias [other than tachycardia, ventricular fibrillation, ventricular flutter, and cardiac arrest]
Other ICD-9 codes related to the CPB:
410.00 - 411.0, 411.81 - 414.9 Ischemic heart disease
425.0 Endomyocardial fibrosis
425.2 Obscure cardiomyopathy of Africa
425.3 Endocardial fibroelastosis
425.5 Alcoholic cardiomyopathy
425.7 Nutritional and metabolic cardiomyopathy
425.8 Cardiomyopathy in other diseases classified elsewhere
425.9 Secondary cardiomyopathy, unspecified
427.69 Other premature beats
428.0 - 428.9 Heart failure
780.2 Syncope and collapse
780.4 Dizziness and giddiness
785.0 - 785.3 Symptoms involving cardiovascular system
794.30 - 794.39 Nonspecific abnormal results of cardiovascular studies
996.03 Mechanical complication due to coronary bypass graft
996.83 Complications of transplanted heart
997.1 Cardiac complications
V12.50 - V12.59 Personal history of diseases of circulatory system
V15.1 Personal history of surgery to heart and great vessels
V17.3 Family history of ischemic heart disease
V17.41 - V17.49 Family history of other cardiovascular diseases
V19.8 Family history of other conditions
V45.81 Aortocoronary bypass status
V45.82 Percutaneous transluminal coronary angioplasty status
V81.0 - V81.2 Special screening for cardiovascular diseases


The above policy is based on the following references:
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  3. Ikeda T, Saito H, Tanno K, et al. T-wave alternans as a predictor for sudden cardiac death after myocardial infarction. Am J Cardiol. 2002;89:79-82.
  4. Ikeda T, Sakurada H, Sakabe K, et al. Assessment of noninvasive markers in identifying patients at risk in the Brugada syndrome: Insight into risk stratification. J Am Coll Cardiol. 2001;37(6):1628-1634.
  5. Adachi K, Ohnishi Y, Yokoyama M. Risk stratification for sudden cardiac death in dilated cardiomyopathy using microvolt-level T-wave alternans. Jpn Circ J. 2001;65(2):76-80.
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