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.