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