MicroVolt T Wave Alternans (MTWA) Clinical Use According to the Guidelines and ICD implants in real world situations.

Comments by D. Marangoni, Editor www.alternans.org

AHA/ACC/ESC Guidelines have issued in 2006 the recommendations for the use of MTWA ( Analytic Spectral Method according to the reference papers) in Class IIA with Level of Evidence A. The recommendations are issued also in reference to the fact that “ICD trials, especially Multicenter Automatic Defibrillator Implantation Trial (MADIT) II, have highlighted the need to develop novel tools in order to identify patients at highest risk of ventricular arrhythmias and SCD”. Chow et al (1) have shown that in ischemic patients with EF<35% with MTWA non-negative, the survival in ICD implanted patients is 50% better than in non implanted patients (in MADIT II the survival was 30% better), and no advantage in survival was found to implant ICD in negative MTWA patients.

Therefore in which patients MTWA can be useful in decision making about ICD implantation?

1. Patients with ICD implant recommendations in Class II. ( i.e dilated cardiomyopathy with EF 31-35% and Heart Failure in Class NYHA II, III). The Multicenter study ALPHA (2) has highlighted that patients in this population with MTWA negative had no sudden death events.

2. Patients with EF at limit (28-32%). In these patients a negative MTWA could be a suggestion to postpone the implant, but a non-negative MTWA could be a suggestion for immediate implant.

3. Many patients and referring doctors are reluctant to primary prevention ICD implants due to relative low reduction in mortality (i.e SCD-Heft) compared to possible complications/ quality of life changes. Actually only 15% of patients with indication to primary prevention have an ICD implanted. As from Chow (2) paper, a positive MTWA test could help patients and referring doctors to take a positive decision to implant.

4. Patients with EP study of difficult interpretation.

5. Budget limitation: in many European countries ICD implants are limited for primary prevention. MTWA test can help in decision making in which patient to implant the limited number of ICD available, with a decision that is better that QRS>120msec. as from Bloomfield, Circulation paper (3)

6. New applications like professional athletes with arrhythmias (4) to guide EP studies or post MI patients with EF>40% to select a higher risk population (5)

1. Chow Tet al. Microvolt T-Wave Alternans Identifies Patients With Ischemic Cardiomyopathy Who Benefit From Implantable Cardioverter-Defibrillator Therapy ( J Am Coll Cardiol, 2007;49:50-58)

2. Salerno et al. Prognostic Value of T-Wave Alternans in Patients With Heart Failure Due to Nonischemic Cardiomyopathy (J Am Coll Cardiol, 2007; 50:1896-1904)

3. Bloomfield 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 (Circulation 2004; 110-: 1885-1889)

4. Inama et al. Microvolt T-Wave Alternans for Risk Stratification in Athletes with Ventricular Arrhythmias: Correlation with Programmed Ventricular Stimulation (A.N.E. 2008;13(1):14–21)

5. Ikeda et al. Predictive Value of Microvolt T-Wave Alternans for Sudden Cardiac Death in Patients With Preserved Cardiac Function After Acute Myocardial Infarction (JACC Vol. 48, No. 11, 2006)