The new paper of Murata
et al. “Effect of long-term beta-blocker therapy on MicroVolt-level T-wave
Alternans in association with the improvement of the cardiac sympathetic
nervous system and systolic function in patients with non-ischemic heart
disease (Circ J. 2003;67:821-5) is interesting because for the first time the
effect of Beta-Blocker is analysed specifically in Non-Ischemic Heart Disease
patients: about 30% of the MTWA positive patients became MTWA negative after
oral Beta Blocker administration.
This can explain the
limited results of MTWA as Arrhythmic Predictor in the Marburg (Grimm et al(1))
Cardiomiopathy study because all the
patients were tested with BetaBlocker washout. In all the other clinical trails
on DCM patients or including DCM patients( Adachi et al (2), Kitamura et al(3),
Hohnloser et al(4), Bloomfield (5), Klingenhaben et al)the patients have been
tested without BetaBlockers washout and MTWA was a good predictor of
Tachyarrhythmic events.
Also in the largest
Clinical Trial of Ikeda (850 patients) in Ischemic patients, the MTWA test was
performed under current therapy.
Therefore it is better
to test all patients under their actual therapy. If the test is indeterminate
because of low Max HR, the test has to be repeated immediately after( in most
of cases the MAX HR is higher in the second test ). Only if the second test is
also indeterminate it is worth to retest the patient with Beta Blocker washout.