MMA Method
Editor
Comments
www.alternans.org
The main
problem of the MMA method is that there is no established criteria for
interpretation ( no prospective clinical paper using a predetermined criteria )
and each new paper is using a new cutpoint for
interpretation ( 5 different cutpoints in 5 different
papers). In all the MMA clinical trials a retrospective analysis was done and
therefore it is impossible to use the MMA method clinically for risk assessment
of Sudden Death :
In Nieminen
et al (1), five alternans cutpoints and
two update factors were evaluated. The optimal combination in this study was
found to be a cutpoint of 65 mV with an update factor of 1/8.
To establish the validity of these parameters, they must be
prospectively tested in a similar patient population. This is particularly important for MMA-TWA,
since previous cutpoints reported in the literature
are not consistent with these values (2-5).
In study of 322 post-MI
patients, Exner et al report an MMA-TWA cutpoint of 5.0 mV after subtraction of
noise, when measured immediately post-exercise (4).
In
a study of 41 patients with
In a retrospective analysis of 44
post-MI patients from the ATRAMI database, the value associated with the 75th
percentile of the control group was used as the cutpoint
and was lead-specific (46.6 mV in lead V1 versus 53.0 mV in lead V5) [5].
In a study of 23 ICD patients and 17
controls (3), Kop et al report that changes in MMA-TWA with mental stress and
bicycle exercise were greater in the ICD group.
While the magnitude of the stress-induced changes in
MMA-TWA were noted, absolute values were not reported and the authors
did not suggest optimal cutpoint values for
discrimination.
An
evaluation of these studies in the aggregate illustrates that there is no
consensus on the optimal cutpoint for positivity of an MMA-TWA test. In addition, the FDA documentation for the GE
MMA-TWA system does not provide guidelines for interpretation; indications for
use state that the system “is intended to provide only the measurements of the
fluctuations of the ST-T wave…No interpretation is generated [510(k) #K032513].”
1. Nieminen, T., et al., T-wave alternans predicts mortality in a population undergoing a clinically indicated exercise test. Eur Heart J, 2007
2. Cox,
V., et al., Predicting arrhythmia-free
survival using spectral and modified-moving average analyses of T-wave alternans. Pacing Clin
Electrophysiol, 2007. 30(3): p. 352-8.
3. Verrier, R.L., et al., Ambulatory
electrocardiogram-based tracking of T wave alternans
in postmyocardial infarction patients to assess risk
of cardiac arrest or arrhythmic death. J Cardiovasc
Electrophysiol, 2003. 14(7): p. 705-11.
4. Exner, D.V., et al., Noninvasive
Assessment of Sudden Death Risk After Myocardial
Infarction - Results of the REFINE Study. Heart Rhythm,
2007. 4(5): p. S94.
5. Kop,
W.J., et al., Effects of acute mental
stress and exercise on T-wave alternans in patients
with implantable cardioverter defibrillators and
controls. Circulation, 2004. 109(15): p. 1864-9.