The Efficacy of Microvolt T-Wave Alternans Testing and Other Noninvasive Risk Stratification Methods (full title below)
- Thu, 5/28/09 - 11:07am
- 0 Comments
- 4133 reads
The Efficacy of Microvolt T-Wave Alternans Testing and Other Noninvasive Risk Stratification Methods for Identifying Patients at Risk of Sudden Cardiac Death
Michael J. Mirro, MD, Medical Director of the Parkview Health System Clinical Research Center in Fort Wayne, Indiana, describes his use of microvolt t-wave alternans (MTWA) testing and other noninvasive risk stratification methods for identifying patients at risk for sudden cardiac death (SCD).
Explain the different methods currently available for screening, such as left ventricular ejection fraction and MTWA.
The public health challenge of preventing sudden cardiac death is significant. Various clinical parameters and noninvasive tests have been studied in an attempt to accurately identify patients who do not have a history of SCD, but who are at risk. These include: 1) structural parameters which predispose one to arrhythmias (reduced ejection fraction, myocardial scar); 2) measures of autonomic tone (heart rate variability, baroreceptor sensitivity); 3) assessment of electrical repolarization abnormalities (T-wave alternans, QT dispersion); and 4) screening for ambient rhythm disturbances like NSVT on Holter.
One consistent finding from numerous trials is that patients with significant left ventricular (LV) dysfunction fall into a high-risk category. As we know from the MADIT II trial, post-MI patients with ejection fractions of 30 percent or less are at high risk and benefit from ICD therapy.1 Similarly, the SCD-HeFT trial showed that patients with reduced EF in the setting of congestive heart failure should be considered for prophylactic ICD implantation to prevent sudden cardiac death.2
While EF has been the most consistent risk factor identified, there are limitations to this approach. For example, there is often significant variation in EF determination based on the imaging modality utilized. In addition, most patients who receive a prophylactic ICD based on low EF never require therapy from the device, illustrating the modest positive predictive value of this approach. Lastly, the majority of SCD events occur in patients with more preserved EF. For these reasons, there has been keen interest over the years to identify other means of identifying patients at risk for SCD that could potentially complement EF.
Microvolt T-wave alternans is a non-invasive diagnostic test that has shown to be predictive of SCD in multiple clinical trials of patients with LV dysfunction.3-5 It has also demonstrated prognostic value in patients with more preserved EF, suggesting that it may be useful in a group that is collectively at lower risk, particularly when combined with other factors that could predispose certain individuals to sudden death.6
For those readers who may be unaware, what is MTWA testing?
1. 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;346:877-883.
2. Bardy GH, Lee KL, Mark DB, et al. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. N Engl J Med 2005;352:225-237.
3. 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;47:456-463.
4. Chow T, Kereiakes DJ, Bartone C, et al. Prognostic utility of microvolt T-wave alternans in risk stratification of patients with ischemic cardiomyopathy. J Am Coll Cardiol 2006;47:1820-1827.
5. Salerno-Uriarte JA, De Ferrari GM, Klersy C, et al. Prognostic value of T-wave alternans in patients with heart failure due to nonischemic cardiomyopathy: Results of the ALPHA study. J Am Coll Cardiol 2007;50:1896-1904.
6. Ikeda T, Yoshino H, Sugi K, et al. Predictive value of microvolt T-wave alternans for sudden cardiac death in patients with preserved cardiac function after acute myocardial infarction: results of a collaborative cohort study. J Am Coll Cardiol 2006;48:2268-2274.
7. Schwartz PJ, Periti M, Malliani A. The long Q-T syndrome. Am Heart J 1975;89:378-390.
8. Kaufman ES, Mackall JA, Julka B, et al. Influence of heart rate and sympathetic stimulation on arrhythmogenic T wave alternans. Am J Physiol Heart Circ Physiol 2000;279:H1248-1255.
9. Cutler MJ, Rosenbaum DS. Explaining the clinical manifestations of T wave alternans in patients at risk for sudden cardiac death. Heart Rhythm 2009;6:S22-S28.
10. Hohnloser SH, Ikeda T, Cohen RJ. Evidence regarding clinical use of microvolt T-wave alternans. Heart Rhythm 2009;6:S36-S44.
11. Chow T, Kereiakes DJ, Onufer J, et al. Does microvolt T-wave alternans testing predict ventricular tachyarrhythmias in patients with ischemic cardiomyopathy and prophylactic defibrillators? The MASTER (Microvolt T Wave Alternans Testing for Risk Stratification of Post-Myocardial Infarction Patients) trial. J Am Coll Cardiol 2008;52:1607-1615.
12. Germano JJ, Reynolds M, Essebag V, et al. Frequency and causes of implantable cardioverter-defibrillator therapies: Is device therapy proarrhythmic? Am J Cardiol 2006;97:1255-1261.
13. Chan PS, Nallamothu BK, Spertus JA, et al. Impact of age and medical comorbidity on the effectiveness of implantable cardioverter-defibrillators for primary prevention. Circ Cardiovasc Qual Outcomes 2009;2:16-24.
14. Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death. Circulation 2006;114:e385-484.
15. Mirro MJ. Strategies for reducing sudden cardiac death: Application of microvolt T-wave alternans testing in clinical practice. Heart Rhythm 2009;6(3 Suppl):S45-8.
16. Costantini O, Hohnloser SH, Kirk MM, et al. The ABCD (Alternans Before Cardioverter Defibrillator) Trial: Strategies using T-wave alternans to improve efficiency of sudden cardiac death prevention. J Am Coll Cardiol 2009;53:471-479.
Post new comment