This policy addresses Microvolt T-wave Alternans testing, a noninvasive electrophysiologic study of the heart.

Medically Necessary:

Microvolt T-wave alternans (beat-to-beat variability in the amplitude of the T-wave) using the spectral analytic method is considered medically necessary for the evaluation of patients at risk of sudden cardiac death who meet the approved criteria for implantable cardioverter defibrillator placement.

Note: Please refer to SURG.00033 Implantable Cardioverter-Defibrillator for the medical necessity criteria for these devices.

Investigational/Not Medically Necessary:

Microvolt T-wave alternans is considered investigational/not medically necessary for all other applications not listed in the criteria above.

Implantable cardioverter-defibrillators (ICDs) have had a major impact on the treatment of ventricular tachyarrhythmias (VT).  ICDs were initially used to treat patients who had survived cardiac arrest or an episode of documented sustained VT.  However, the majority of patients who die from sudden cardiac death (SCD) have not had such an event.  In 2000, the Multi-Center Unsustained Tachycardia Trial (MUSTT) demonstrated that, in patients with a prior myocardial infarction, left ventricular ejection fraction ≤ 0.40, and unsustained ventricular tachycardia, invasive electrophysiologic study (EPS) was a poor predictor of future sustained ventricular arrhythmic events. (Buxton 2000).  Prior to this study, EPS had been the primary diagnostic tool for risk stratification and selection of ICDs for individual patients. 

The MADIT II (2002) and SCD-HeFT(2005) primary prevention trials were the two pivotal studies that established the utility of ICD therapy for the primary prevention of SCD  in patients without a history of prior sustained VT.  MADIT II addressed ICD use in patients with prior myocardial infarction and left ventricular ejection fraction (LVEF) ≤ 0.30.  SCD-HeFT addressed ICD therapy in patients with LVEF ≤ 0.35 with New York Heart Association (NYHA) class II or III heart failure on the basis of either ischemic or non-ischemic cardiomyopathy.  Although the absolute reductions in annual mortality in the MADIT II (4.0%) and SCD-HeFT (2.5%) trials were modest, these studies led the Centers for Medicare and Medicaid Services (CMS) to approve Medicare coverage for ICD therapy for patients meeting criteria established in these trials.

Although the validity of the ICD prophylaxis trials has been established, there is a need for better risk stratification to target therapy given the inconvenience, risks, and resource implications of implanting ICDs in all patients who meet the MADIT II or SCD-HeFT criteria.  Studies of microvolt T-wave Alternans (MTWA) have focused on the capability of this test to predict fatal arrhythmias and sudden cardiac death, in patients with a history of myocardial infarction, congestive heart failure, or cardiomyopathy.  These high risk patients may be treated with drugs to suppress arrhythmias, or undergo implantation of an ICD.  A positive MTWA test result is one of many risk factors that have been investigated for identifying candidates for primary prevention with an ICD.  Others include left ventricular ejection fraction (LVEF), arrhythmias detected on Holter monitor, electrophysiologic studies, heart rate variability, baroreceptor sensitivity and signal-averaged electrocardiography (addressed separately in Policy MED.00074).  Signal-averaged electrocardiography (SAECG) measures beat-averaged conduction, while MTWA measures beat-to-beat variability in T wave amplitude, using specialized signal processing algorithms, (i.e., spectral analysis).

In 2003, CMS conducted a subgroup analysis of MADIT II data that looked at the impact of QRS duration on patient outcomes.  Based on this analysis, CMS announced its intent to limit coverage of ICDs to patients meeting the criteria for the MADIT-II trial with a QRS duration greater than 120 ms, thereby cutting member eligibility by one-third.  This strategy was criticized by those who pointed out the hazards of post-hoc subgroup analysis, and CMS lifted this restriction in January 2005.  In partial response to this planned restriction, Bloomfield (2004) compared the predictive value of MTWA with QRS duration, in patients who would meet the MADIT II criteria. The study population was drawn from a multi-institutional epidemiologic study that examined the prognostic significance of T-wave alternans in patients with left ventricular dysfunction.  Of the 549 evaluable patients in the study, 177 also met the MADIT II criteria (prior MI, LVEF ≤ 0.30).  This subgroup formed the study group.  The mean patient follow-up was 20 months, and the primary outcome was all-cause mortality.

The two-year mortality rate in patients with an abnormal T-wave alternans test was 17.8%, compared with 3.8% in those with a normal T-wave alternans study.  In contrast, the mortality rate for patients with a QRS duration of greater than 120 ms was not significantly different from those with a normal QRS interval.  The authors of this study concluded that the MTWA is a superior risk predictor than the QRS interval.  Further, the authors proposed that a normal MTWA test might be used to deselect patients for an ICD, who would, otherwise, meet the criteria established by the results of the MADIT II trial. 

 In a meta-analysis by Gehi, et al (JACC, 2005), the predictive value of MTWA for arrhythmic events in a wide variety of populations was studied.  Data from 19 studies published between 1990 and 2004  (2,608 patients) across a wide range of conditions was collected.  Overall, the negative predictive value (NPV) was 97% and the positive predictive value (PPV) was 19.3% at average of 21 months follow-up.  There was no difference in PPV between ischemic and non-ischemic heart failure subgroups, but the PPV varied significantly depending on the population studied.  The authors pointed out that many of the early studies used non-standard definitions of “abnormal” MTWA and that the incremental prognostic value of MTWA, when used with other methods of risk stratification, remains unclear.

In a recent review article, Armoundas, et al (2005) summarized annual ventricular tachyarrhythmia event (VTE) rates observed in prospective microvolt T-wave alternans studies published between 2000 and 2003, performed in patients with a history of ischemic or non-ischemic heart disease and reduced ejection fraction who were not selected on the basis of a history of ventricular tachyarrhythmias.  The total number of patients followed was 1, 811.  The weighted average annual VTE rate was 8.4% in MTWA-positive and 1.2% in MTWA-negative patients yielding a hazard ratio of 7.  In this review, comparison was also made of annual all-cause mortality rates between patients (with and without ICD) in the SCD-HeFT and MADIT II trials to those in prospective MTWA studies by Bloomfield (2004), Hohnloser (Lancet 2003), Constantini (2004) and Grimm (2003) who were followed without ICD placement.  In the MADIT II trial, annual mortality was 13.2% for patients without ICD placement and 9.2% for those with ICD.  In the SCD-HeFT trial, the annual mortality without ICD was 10.4% and 7.4% for those with ICD.  Combining the two trials of 3,753 patients, the annual mortality with out ICD was 10.4% and 7.4% with ICD.

The authors concluded that since the average annual rate of fatal and nonfatal ventricular tachyarrhythmic events among patients testing negative for MTWA (1.2%) is so low in the pooled analysis of the prospective studies cited above, it is unlikely that such patients would benefit from ICD therapy.  In fact, the mortality (2%) was lower among MTWA negative patients who did not receive implantable defibrillators than that observed in the MADIT II (9.2%) and SCD-HeFT (6.5%) patients who received ICDs.

Recently, Bloomfield, et al (JACC, 2006) updated an earlier study mentioned above of 587 patients at 11 sites between 1996 and 2003; all had LVEF ≤ 0.40.  Eight had ICDs placed before study enrollment, and 61 after enrollment.  There was no difference in the ICD implant rate between MTWA test normal and MTWA test abnormal, indicating that the MTWA test results were not used to select patients for prophylactic ICDs.  At 24 months, a significant portion (30%) were either censored or lost to follow-up.  Reasons for not reaching two years of follow up were: died (n=40), censored because of heart transplant (n=31), enrolled less than two years before close out date (n=129), and lost or refused follow up (n=22).  Most patients were followed for the entire two years.

During 20 months of follow-up, 51 end point events were observed; 40 deaths from any cause and 11 non-fatal sustained VTE.  The event rate in the group with normal MTWA was 2.5%, compared to 15.0% for those with a positive MTWA.  Forty-seven events occurred in the group with an abnormal MTWA test.  Abnormal MTWA included positive tests (n=162) where the event rate was 12.3% and indeterminate tests (n=198) where the two-year event rate was even higher at 17.5%.   Greater than 90% of the indeterminate tests were due to physiologic reasons, such as ectopy, non-sustained T-wave alternans, or an inability to achieve a heart rate of 105 beats/min.   Other studies have shown that positive and indeterminate MTWA tests have similar event rates (Hohnloser 2003; Bloomfield 2002).  Only four events occurred in patients with a normal MTWA test: one arrhythmic death, one non-cardiac death, and two non-fatal sustained ventricular arrhythmias.  All of the normal MTWA events occurred in the group with ischemic cardiomyopathy.  The NPV of a normal MTWA test for survival was 97.5%.  The hazard ratio for primary end point was 6.5 at two years, p<0.001.  A cohort with LVEF ≤ 0.30 in this updated report was increased to an N of 405.  For this subgroup, the two-year event rate was 16.1% for MTWA abnormal and 3.5% for MTWA normal with a hazard ratio of 5.0 (95% CI [1.8-14.1]).

In the sample of patients with LVEF ≤ 0.40, adjusting for LVEF did not add to the prognostic information provided by MTWA.  When MTWA and LVEF were separately analyzed in a multivariate Cox model, MTWA remained a strong independent predictor.  It is notable that patients with a normal MTWA test and LVEF ≤ 0.30 had a lower two-year event rate (3.5%) than patients with an abnormal MTWA test and LVEF between 0.31 and 0.40 (11.8%).

Chow, et al (2006) recently published the results of a study to determine if MTWA is an independent predictor of mortality in patients with ischemic cardiomyopathy by controlling a variety of baseline differences between MTWA negative and non-negative (positive + indeterminate) patients.  Enrolled were 768 consecutive patients with ischemic cardiomyopathy LVEF ≤ 0.35 with no prior history of ventricular arrhythmia.  Identified were 514 (67%) of the study group with non-negative MTWA baseline test results.  Mean follow-up for the entire group was 18 ± 10 months.  Primary end point was all-cause mortality, but secondary endpoints including, cause specific mortality (arrhythmic death) and the delivery of ICD shocks in those patients with ICDs, were also calculated. 

Multivariate analysis was then used to determine the association between MTWA testing and mortality after adjusting for a number of clinical characteristics including age, LVEF, QRS duration, co-morbidities, and medications (aspirin, ACEI, beta blocker, digoxin, class I or III antiarrhythmic, statin, and spironolactone).  After multivariable adjustment, a non-negative MTWA was associated with a higher risk for all cause mortality HR=2.24 (p=0.002) and arrhythmic mortality HR-2.29 (P=0.049) but not for non-arrhythmic mortality HR=1.77 (p=0.13). Looking only at patients with an ejection fraction ≤ 0.30, non-negative MTWA was also associated with a higher risk for all cause mortality HR=2.10 (p=0.012).  Excluding those with “indeterminate” MTWA tests, a “positive” MTWA continued to show a HR of 2.08 (p=0.01). 

Chow, et al concluded that MTWA testing in ischemic cardiomyopathy remained an independent predictor even after controlling for multiple variables, and that the increased risk associated with a non-negative MTWA result is due to a higher rate of arrhythmic mortality.  These results are less impressive (i.e. lower hazard ratio)  than earlier studies using MTWA testing in patients with ischemic cardiomyopathy where adjustment was not made for potential differences in baseline characteristics between patients with non-negative and negative MTWA results.  The strength of this study is the adjustment for ICD status and a number of demographic, clinical and treatment variables.

A significant limitation to this study is the lack of adjustment for New York Heart Association functional class, which may be a cause for residual confounding in this cohort study.  It is notable that the arrhythmic mortality hazard ratio was actually higher, but not to a statistical significance (p=0.09), for MTWA-indeterminate patients than for MTWA-positive patients.  In this study, 77% of patients testing “indeterminate” did so as a result of either frequent ventricular ectopy or an inability to reach an adequate heart rate (>105 beats/min), conditions which do not allow MTWA measurement.   The “indeterminate” test results in these patients my reflect underlying heart disease or physical deconditioning that may predispose these patients to similar or even higher mortality rates than MTWA positive patients.

CONCLUSION:

Since the absolute reduction in annual mortality in the MADIT II (4.0%) and SCD-HeFT (2.5%) trials were small, a very limited portion of proposed ICDs (using MADIT II and SCD-HeFT criteria alone) would deliver life-saving therapy in a given year.  Bardy (2005) calculated that in the SCD-HeFT study only 5.1% of implanted ICDs fired appropriately on an annual basis, leading to the 2.5% absolute reduction in annual mortality.  The concern raised is for the vast majority of patients in whom the ICD never discharges that are subject to the morbidity and mortality associated with ICD implantation without benefit.  The risks of ICD therapy include wound infection, inappropriate shocks, lead breakage, cardiac perforation, device failure and vascular complications (Pavia 2001).  Reynolds, et al (2006) recently analyzed Medicare Provider Analysis and Review (MedPAR) files for 2003 and identified 30,984 admissions for ICD implantation.  One or more of eight complications were recorded in 10.8% of admissions.  The majority were described as “mechanical complication of the ICD” and “hemorrhage/hematoma.”  These concerns have been heightened following the disclosure of recent ICD failures and product recalls.

The studies cited above appear to adequately establish the negative predictive accuracy of MTWA in patients with left ventricular dysfunction.  Because the sudden cardiac death rate is so low in MTWA-negative patients, a prospective randomized trial with a mortality endpoint comparing ICD versus non-ICD in MTWA negative patients with LV dysfunction would need to be many times larger than the MADIT-II and SCD-HeFT trials combined to be adequately powered.  Armoundas (2005) and others working in this area of clinical research contend that it is unlikely that such a study will be performed.

An industry sponsored trial, MASTER I, which began October 2003 with data entry closure October 2006 is scheduled for completion February 2007.  This study is a non-randomized, interventional trial of approximately 650 “MADIT II- like” patients, (post MI LVEF ≤ 0.30) who will be assessed with MTWA testing prior to ICD placement and followed for 18 months.  Primary outcome is VT event free survival with secondary outcomes to include all ventricular events, identify predictors of life threatening ventricular arrhythmias and occurrence of VTE based on last MTWA results. (clinicaltrials.gov)

At this time, neither the American College of Cardiology (communication June 6, 2006)) nor CMS recommend withholding, based on MTWA testing, an ICD from a patient meeting the criteria established in randomized clinical trials of ICD therapy (MADIT-II/SCD-HeFT).  However, both CMS and the American College of Cardiology do consider MTWA a medically useful diagnostic test for the evaluation of patients with LV dysfunction at risk of sudden cardiac death.  MTWA testing appears to be a useful risk stratification tool to identify which patients with LV dysfunction are at negligible risk of SCD.  For patients considered candidates for ICD placement, evidence suggests that a negative MTWA test could be useful for identifying low-risk patients unlikely to benefit from, and who might even experience worse outcomes from, ICD placement.  In this setting, MTWA is considered medically necessary when used in conjunction with the patient’s history, exam, other diagnostic test information, and preferences to help guide physicians as they counsel at risk patients in primary prevention therapies for SCD.

Epidemiology

Sudden cardiac death is one of the most common causes of death after a myocardial infarction or in patients with dilated cardiomyopathy, and there is intense interest in risk stratification to target therapy.  In the United States, sudden cardiac death results in approximately 400,000 deaths annually. Ventricular tachyarrhythmias, where the heart beats very fast due to abnormal ventricular contractions, are the most common cause of sudden cardiac death.  Examples of ventricular tachyarrhythmias include ventricular tachycardia (rapid ventricular contractions) and ventricular fibrillation (very rapid, weak, irregular and ineffective ventricular contractions).  Patients most at risk for these heart rhythm disturbances include those with a recent myocardial infarction (heart attack), congestive heart failure, coronary artery disease, a family history of major ventricular arrhythmias, and/or dilated cardiomyopathy (disease of the heart muscle that causes the heart to get larger or dilate).  

Functional Description

Microvolt T-wave alternans (MTWA) refers to a beat-to-beat electrocardiographic (EKG) variability in the amplitude of the T-wave, which was first recognized by Lewis in 1910.  T-wave alternations are felt to represent abnormalities in intracellular calcium handling that may provoke re-entrant ventricular tachyarrhythmias (Armoundas 2002).  A routine EKG cannot detect these small fluctuations, and thus, this test requires specialized sensors to detect the fluctuations and computer algorithms to evaluate the results.  T-wave alternans is a provocative test that necessitates gradual elevation of the heart rate to above 110 beats per minute and can be performed in conjunction with an exercise tolerance stress test.

The magnitude of the T-wave alternans is measured as microvolts.  A value of 1.9 microvolts or greater above baseline is considered a positive test.  T-wave alternans is heart- rate dependent and is usually measured while the heart rate is elevated for several minutes by means of exercise, pacing or pharmacologic stress.  The test can be performed by a supervised technician in approximately 30 minutes.  Multiple electrode noise-reducing sensors are used to record the EKG signals.  Specialized signal-processing algorithms to process the signals are used to determine the amplitude of the alternans over background noise.  For a positive result, the MTWA test must detect sustained alternans meeting amplitude criteria and be consistently present above an onset heart rate of 110 beats/min or less.  A negative test does not meet the alternans amplitude criterion; there must be at least one minute of data collected at a heart rate of 105 beats/minute or higher without significant alternans.  Tests that do not qualify as positive or negative are classified as “indeterminate.” 

Alternatives to MTWA testing for arrhythmia risk stratification include electrophysiologic testing, ejection fraction testing, EKG testing, continuous Holter EKG monitoring, heart rate variability, signal-averaged EKG, and baroreceptor sensitivity testing.

There are several devices, along with processing software, that have been FDA approved for performing MTWA, including the HeartWave Alternans Processing System™, the Model APS Alternans Processing System™, and the CH 2000 Cardiac Diagnostic System™.  These instruments are manufactured by Cambridge Heart, Inc., Bedford, MA.

Proposed Benefits

The presence of T-wave alternans has been investigated as a risk factor for fatal arrhythmias and sudden cardiac death in patients with a history of myocardial infarction (MI), cardiomyopathy, or other cardiac conditions. Patients with a positive T-wave alternans result are hypothesized to show an increased risk for dangerous ventricular arrhythmias.  A negative T-wave alternans test is proposed as a method to exclude the need for, and eliminate the risk of, placement of an implantable cardioverter-defibrillator.

Possible Risks

MTWA is a non-invasive physiological test and poses little risk to the patient.  However, the exercise necessary for the test may, in rare cases, lead to arrhythmias, and the patient must be closely monitored. As a technique to deselect a patient for implantation of an ICD, there is an associated risk of sudden cardiac death, if results of the T-wave alternans testing were to incorrectly identify the patient as low risk.

Baroreceptor sensitivity testing:  this test evaluates for patient propensity toward nervous system effects on the heart rate and rhythm, when the patient becomes frightened, overly stressed, overtired, etc.

Electrophysiologic Studies (EPS):  an invasive test where a catheter with an electrode is inserted into the ventricle chamber of the heart for analysis of the potential for arrhythmias, which are induced and then treated with intravenous medications.

Holter monitoring:  this noninvasive device allows for continuous ambulatory heart rhythm recording for a limited period of time, usually 24-48 hours, with subsequent physician interpretation of the recorded results.

Left ventricular ejection fraction (LVEF):  the percentage of the total blood volume in the left ventricle, which is ejected or pumped out into the bloodstream when the heart contracts during each heartbeat; this percentage is used as a measure of heart health and function.

T-wave alternans: the heartbeat- to-heartbeat variability in the shape of the T-wave on the EKG.

The following codes for treatments and procedures applicable to this policy are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member’s contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Medically Necessary, when criteria are met:

CPT

ICD-9 Diagnosis

When services are Investigational/Not Medically Necessary:
For the procedure code listed above, when criteria are not met or when the code describes a procedure indicated in the Policy section as investigational/not medically necessary.

Peer Reviewed Publications:

1. Adachi K, Ohnishi Y, Shima T, et al. Determinant of microvolt-level T-wave alternans in patients with dilated cardiomyopathy. J Am Coll Cardiol. 1999; 34(2):374-80.
2. Armoundas AA, Rosenbaum DS, Ruskin JN, et al. Prognostic significance of electrical alternans versus signal averaged electrocardiography in predicting the outcome of electrophysiological testing and arrhythmia-free survival. Heart. 1998; 80(3):251-6.
3. Armoundas A, Tomaselli G, Esperer H. Pathophysiological basis and clinical application of T-wave alternans J Am Coll Cardiol. 2002; 40: 207-17.
4. Armoundas A, Hohnloser S, et al. Can microvolt T-wave alternans testing reduce unnecessary defibrillator implantation? Nature Clinical Practice. 2005; vol 2(10):522-8.
5. Baravelli M, Salerno-Uriarte D, Guzzetti D, et al. Predictive significance for sudden death of microvolt-level T wave alternans in New York Heart Association Class II congestive heart failure patients: a prospective study.  Int J Cardiol. 2005; 105(1):53-7.
6. Bardy GH, et al. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. N Enl J Med. 2005; 352:225-37.
7. Bigger JT. Editorials: Expanding indications for implantable cardiac defibrillators. N Engl J Med. 2002; 346(12):931-33.
8. Bloomfield DM, et al. Interpretation and classification of microvolt T wave alternans tests. J Cardiovasc Electrophysiol. 2002; 13:502-12.
9. Bloomfield DM, Bigger JT, Steinman RC, et al. Microvolt T-Wave alternans and the risk of death or sustained ventricular arrhythmias in patients with left ventricular dysfunction.  J Am Coll Cardiol. 2006; 47(2):456-63.
10. Bloomfield DM, Steinman RC, Namerow PB, et al.  Microvolt T-wave alternans distinguishes between patients likely and patients not likely to benefit from implanted cardiac defibrillator therapy: A solution to the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II Conundrum.  Circ. 2004; 110:1885-89.
11. Buxton AE, et al. Electrophysiologic testing to identify patients with coronary artery disease who are at risk for sudden death.  Multicenter Unsustained Tachycardia Trial Investigators, N Engl J Med. 2000; 342:1937-1945.
12. Chow T, et al. Prognostic utility of microvolt T-wave alternans in risk stratification of patients with ischemic cardiomyopathy.  J Am Coll Cardiol. 2006; 47(9):1820-27.
13. Costantini O, et al. Patients with a nonischemic cardiomyopathy and a negative T-wave alternans stress test are at low risk of death. Circulation. 2004; 110(suppl III):667.
14. Gehi AK, Stein RH, Metz LD, et al. Microvolt T-Wave alternans for the risk stratification of ventricular tachyarrhythmic events.  J Am Coll Cardiol. 2005; 46(1):75-82.
15. Gold MR, Bloomfield DM, Anderson KP, et al. A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification. J Am Coll Cardiol. 2000; 36(7):2247-53.
16. Grimm W, et al. Noninvasive arrhythmia risk stratification in idiopathic dilated cardiomyopathy: results of the Marburg Cardiomyopathy Study. Circulation. 2003; 108:2883-2891.
17. Grimm W. Quantitative assessment on microvolt T-wave alternans (MTWA) in 204 consecutive patients with congestive heart failure.  J Cardiovasc Electrophysiol. 2005; 16(11):1263-64.
18. Hennersdorf MG, Niebch V, Perings C, et al. T-wave alternans and ventricular arrhythmias in arterial hypertension. Hypertension. 2001; 37(2):199-203.
19. Hohnloser SH, Klingenheben T, Li YG, et al. T-wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: prospective comparison with conventional risk markers. J Cardiovasc Electrophysiol. 1998; 9(12):1258-68.
20. Hohnloser SH, et al. T wave alternans negative coronary patients with low ejection and benefit from defibrillator implantation. Lancet. 2003; 362:125-26.
21. 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(1):79-82.
22. Ikeda T, Sakata T, Takami M, et al. Combined assessment of T-wave alternans and late potentials used to predict arrhythmic events after myocardial infarction. A prospective study. J Am Coll Cardiol. 2000; 35(3):722-30.
23. Klingenheben T, Zabel M, D’Agostino RB, et al. Predictive value of T-wave alternans for arrhythmic events in patients with congestive heart failure. Lancet. 2000; 356(9230):651-2.
24. Lepor NE. Microvolt T-wave alternans testing to target patients for ICD implantation and prevent sudden cardiac death.  Rev Cardiovasc Med. 2006; 7(1):42-4.
25. Lewis T. Notes upon alternation of the heart.  Q J Med. 1910; 4:141-144.
26. Mathew ST, Patel ND, Singh BK. T-wave alternans, a potential non-invasive marker for ventricular arrhythmias. Acta Cardiol. 2005; 60(6):639-49.
27. Moss AJ, Zareba W, Hall WJ, et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002; 346(12):877-83.
28. Narayan SM.  T-Wave alternans and the susceptibility to ventricular arrhythmias.  J Am Coll Cardiol. 2006; 47(2):269-81.
29. Pavia S and Wilkoff B. The management of surgical complications of pacemaker and implantable cardioverter-defibrillators. Curr Opin Cardiol. 2001; 16:66-71.
30. Reynolds MR, et al. The frequency and incremental cost of major complications among Medicare beneficiaries receiving implantable cardioverter-defibrillators.  J Am Coll Cardiol. 2006; 47(12):2493-7.
31. Richter S, Duray G, Hohnloser H. How to analyze T-wave alternans.  Heart Rhythm. 2005; 2(11):1268-71.
32. Tapanainen JM, Still AM, Airaksinen KE, et al.  Prognostic significance or risk stratifiers of mortality, including T-wave alternans, after acute myocardial infarction: Results of a proposective follow-up study.  J Cardiovasc Electrophysiol. 2001; 12:645-52.
    

Government Agency, Medical Society, and Other Authoritative Publications:

1. Alternans before cardioverter defibrillator (ABCD) Trial: study to compare TWA test and EPS test for predicting patients at risk for life-threatening heart rhythms.  St. Jude Medical; Cambridge Heart MetroHealth Medical Center (ongoing unpublished study Start Date: April 2001).  Study ID No. G010050.  Clinical Trials Identifier: NCT00187291.  Available at: http://clinicaltrials.gov/show/NCT00187291.  Accessed on: August 15, 2006.
2. Antman EM, Anbe DT, Armstrong PW, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to revise the 1999 Guidelines for the Management of Patients with Acute Myocardial Infarction).  Circ. 2004; 110:e82-e293.  Available at: http://www.acc.org.  Accessed on: August 15, 2006.
3. Blue Cross Blue Shield Association. Microvolt T-Wave alternans testing to risk stratify patients being considered for ICD therapy for primary prevention of sudden death. TEC Assessment, 2005; 20(9).
4. Centers for Medicare and Medicaid Services.  National Coverage Determination: Microvolt T-Wave Alternans (MTWA). NCD #20.30. Effective: March 21, 2006.  Implementation Date: April 3, 2006.  Available at: http://www.cms.hhs.gov.  Accessed on: August 15, 2006.
5. Kadish AH, Buxton AE, Kennedy HL, et al. ACC/AHA clinical competence statement on electrocardiography and ambulatory electrocardiography: a report of the American College of Cardiology/American Heart Association/American College of Physicians-American Society of Internal Medicine Task Force on Clinical Competence (ACC/AHA Committee to develop a Clinical Competence Statement on Electrocardiography and Ambulatory Electrocardiography).  Circ. 2001; 104:3169-78.  Available at: http://circ.ahajournals.org/cgi/content/full/104/25/3169.  Accessed on: August 15, 2006.
6. Strickberger SA, Benson DW, Biaggioni I, et al. AHA/ACCF Scientific Statement on the Evaluation of Syncope: from the American Heart Association Councils on Clinical Cardiology, Cardiovascular Nursing, Cardiovascular Disease in the Young, and Stroke, and the Quality of Care and Outcomes Research Interdisciplinary Working Group; and the American College of Cardiology Foundation in Collaboration with the Heart Rhythm Society.  J Am Coll Cardiol. 2006; 47:473-84.  Available at: http://www.americanheart.org.  Accessed on: August 15, 2006.
7. Hayes, Inc. Hayes Medical Technology Directory. Microvolt T-wave Alternans to Identify Risk of Ventricular Arrhythmias and Sudden Cardiac Death. Lansdale, PA: Hayes, Inc: July 31, 2002. Search updated May 13, 2006.
8. Microvolt T-Wave alternans testing for risk stratification of post-MI patients (MASTER) Trials (ongoing unpublished trials).  MASTER I Trial completion date: 02/2007; MASTER II completion date: 02/2008. Sponsored by Medtronics, Inc. and Cambridge Heart, Inc.  Available at: http://www.clinicaltrials.gov/ct/show/NCT00305240?order=1  Accessed on: August 16, 2006.
9. National Institutes of Health. National Heart, Lung, and Blood Institute. Prognostic Significance of T-Wave Alternans (ongoing unpublished study timeframe duration: 2000-2005). Currently in data analysis stage. Principal investigator: Bigger JT.
   

1. American Heart Association. Available at: http://www.americanheart.org/presenter.jhtml?identifier=1200000  Accessed on: August 15, 2006. 
2. American College of Cardiology. Available at: http://www.acc.org/  Accessed on: August 15, 2006. 

Microvolt T-Wave Alternans
MTWA
T-Wave Alternans
 

Federal and State law, as well as contract language, including definitions and specific contract provisions/exclusions, take precedence over Medical Policy and must be considered first in determining eligibility for coverage. The member's contract benefits in effect on the date that services are rendered must be used. Medical Policy, which addresses medical efficacy, should be considered before utilizing medical opinion in adjudication. Medical technology is constantly evolving, and we reserve the right to review and update Medical Policy periodically.

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