Use of Microvolt T-wave Alternans Testing in Clinical Practice to Reduce Sudden Cardiac Arrest and Death

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Left, the relation between T-wave alternans and arrhythmia-free survival in 66 patients. Kaplan-Meier life table arrhythmia-free survival is compared in patients with and without significant T-wave alternans. Note that the presence of T-wave alternans str
Arrhythmia-free survival in 102 post-myocardial infarction patients based on MTWA classification [Reprinted with permission from J Am Coll Cardiol 2000;35:722–730, (Figure 4A)]..
Restitution curve illustrating that action potential alternans is initiated when the diastolic interval falls to a value where the slope of the curve exceeds unity [Reprinted with permission from BMJ Books, from Repolarisation Alternans; 2001 (Figure 25.3
Trend plot of treadmill MTWA test in a patient with sustained alternans. Sustained alternans is defined as alternans with Valtalt >= 1.9 microvolts and alternans ratio >= 3 consistently present either at rest or above a patient-specific onset heart rate.
Arrhythmia-free survival in patients with implanted ICDs according to MTWA classification (left panel) and EPS classification (right panel) [(Reprinted with permission from J Cardiovasc Electrophysiol 1998;9:1258–1268 (Figures 1A and 1B)].
Arrhythmia-free survival in patients undergoing electrophysiologic testing according to MTWA classification (left panel) and EPS classification (right panel) [Reprinted with permission from J Am Coll Cardiol 2000:36,2247–2253 (Figures 1A and 1B)].
Arrhythmia-free survival in patients with heart failure according to MTWA classification [Reprinted with permission from Lancet 2000;356:651–652, (Figure)].
Arrhythmia-free survival in patients with non-ischemic dilated cardiomyopathy [Reprinted with permission from PACE 1999;22(Suppl II):860, (Figure)].
Author(s): 

Richard J. Cohen, MD, Ph

Microvolt T-Wave Alternans (MTWA) is a new non-invasive method for identifying patients at increased risk of cardiac arrest and sudden cardiac death from ventricular arrhythmias. MTWA can be measured during a routine exercise stress test during pharmacologic stress or during cardiac pacing. MTWA has been successfully applied to patients both with and without coronary artery disease. Its clinical performance compares favorably with that of other non-invasive risk stratifiers and invasive electrophysiologic study (EPS). The event rate during follow-up among patients who test MTWA-positive is comparable to that of patients with a positive EPS, whereas the event rate among MTWA-negative patients tended to be lower than among EPS-negative patients. In particular, the low event rate during follow-up among patients with a negative MTWA test renders MTWA a suitable non-invasive means for the initial evaluation of patients potentially at risk for ventricular arrhythmias. Patients suitable for MTWA testing include patients presenting with a history suggestive of ventricular arrhythmias, patients with left ventricular dysfunction, and patients at least 4-6 weeks after myocardial infarction. Patients who test MTWA-positive can proceed to invasive study and/or therapy, whereas patients who test negative in most cases can be managed conservatively. In addition, MTWA can be measured during cardiac pacing in the electrophysiology laboratory to provide an additional endpoint in addition to the outcome of programmed ventricular stimulation, or as a means to non-provocatively assess ventricular stability in patients being evaluated or treated for supraventricular arrhythmias. MTWA testing can increase referrals of appropriate patients for further electrophysiologic evaluation and/or therapy.

Sudden cardiac death (SCD) from ventricular tachyarrhythmia represents a major public health problem accounting for approximately 300,000-400,000 deaths per year in the United States.1 In recent years, there have been dramatic advances in therapy for the prevention of SCD due to ventricular tachyarrhythmias. Specifically, the development of the implantable cardioverter/defibrillator (ICD) has provided an effective and specific preventative treatment for patients known to be at high risk for sudden cardiac death.2-5 The ICD, however, represents an expensive therapy that is applied only in patients known to be at high risk.
Pharmacologic therapy also has advanced. Beta-blockers have been shown to reduce total mortality and arrhythmic death in patients with coronary artery disease.6 Beta-blockers,6,7 angiotensin-converting enzyme (ACE) inhibitors,8 and aldosterone antagonists9 have been shown to reduce total mortality and arrhythmic death in patients with left ventricular dysfunction. Amiodarone has been shown to reduce ventricular tachyarrhythmic events in patients with heart failure.10-12 Sotalol has been shown to reduce the frequency of appropriate ICD discharges for ventricular tachycardia and ventricular fibrillation.13

References: 

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