Aetna considers measurement of microvolt T-wave alternans 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 measurement of microvolt T-wave alternans diagnostic testing using the spectral analytic method experimental and investigational for all other indications.

See  CPB 585 - Cardioverter-Defibrillators.

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, Holter monitoring, and signal-averaged late potentials are the principal noninvasive means of determining the risk of ventricular arrhythmias after myocardial infarction.  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 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 MTWA in a variety of population settings, including subjects with congestive heart failure (CHF), ischemic CHF, non-ischemic CHF, dilated cardiomyopathy, hypertrophic cardiomyopathy, post myocardial infarction, 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 microvolt T-wave alternans 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 microvolt T-wave alternans 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, microvolt T-wave alternans 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 microvolt T-wave alternans 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 microvolt T-wave alternans 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 two 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 microvolt T-wave alternans 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 microvolt T-wave alternans 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 microvolt T-wave alternans.  The decision memorandum explained that, although algorithms other than spectral analysis have been used to measure microvolt T-wave alternans (e.g., modified moving average), CMS identified no peer-reviewed published articles discussing these other algorithms.

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