Sustained T-wave Alternans
During Exercise and Pacing: Feasibility and Relation to Other Risk Variables in
Post-AMI Patients with Depressed Left Ventricular Function
Heikki V. Huikuri, MD, PhD, Vesa Jokinen, MD, Pekka Raatikainen, MD, Vesa
Virtanen, MD, Antti Hedman, MD and Juha Hartikainen, MD. University of Oulu,
Division of Cardiology, Oulu, Finland, University of Tampere, Division of
Cardiology, Tampere, Finland, University of Kuopio, Division of Cardiology,
Kuopio, Finland
Bacground:
CARISMA is a multicenter study enrolling patients with an acute myocardial
infarction (AMI) and ejection fraction (EF) < 40 %. All patients
receive an automatic loop-recorder to document arrhythmias and extensive
risk-stratification tests, e.g. T-wave alternans (TWA), Holter, heart rate
variability, signal-averaged ECG, QT-dispersion and electrophysiologic testing,
are performed 6 weeks post-AMI.
Methods
and Results: This substudy evaluated the feasibility of exercise
testing (Ex), atrial (A) pacing, and simultaneous ventricular and atrial (V+A)
pacing in TWA analysis, and the relation between TWA and the other risk
markers. In 80 consecutive patients, TWA was indeterminate in 34 (43%) pts
during Ex, 21 patients (26%) during A pacing, and only in 7 patients (9%)
during V+A pacing. The main reasons for indeterminate TWA were inability to
reach the target heart rate (= 105 bpm) (n=26) or lack of 1:1 A-V conduction
during A pacing at heart rate > 105 bpm (n=8). Sustained TWA was observed in
41%, 61%, and 55% of patients during Ex, A, and V+A pacing, respectively. The
TWA concordance between Ex and A pacing was 79%, Ex and V+A pacing 71%, and in
95% between the two pacing modes. Patients with positive TWA in all tests had
lower EF (28± 7% vs. 35± 9%, p<0.01) and wider QT-dispersion (99± 44 ms vs.
67± 38 ms, p<0.01) than those with inconsistent test result. Positive TWA
was not related to any other risk variable.
Conclusions:
Pacing, V+A in particular, provides a feasible means to assess TWA among the
post-AMI patients with depressed left ventricular function, if they have an
indeterminate test result during Ex. The prognostic value of TWA measurements
will be evaluated in a larger sample of CARISMA patients during the future
follow-up.