T-Wave Alternans During Ambulatory Ischemia in Patients with Stable Coronary Disease

Background: T-wave alternans is a marker of vulnerability to ventricular tachyarrhythmias and has been documented during myocardial ischemia associated with angioplasty, bypass graft occlusion, and episodes of Prinzmetal's variant angina. We examined whether this phenomenon was present during ambulatory ischemia in ten patients randomly selected from the placebo phase of the Angina and Silent Ischemia Study [ASIS]. Methods: The eligibility criteria for participation in the ASIS study were stable coronary disease, a positive exercise stress test, and verified ischemic episodes during ambulatory ECG (AECG) monitoring. For each patient, one ischemic episode was analyzed which met the criteria of > 2-mm ST segment depression for > 3 minutes with a relatively stable ST segment baseline of > 1 hour preceding the index episode. T-wave alternans was measured using the spectral analytical technique of complex demodulation. Results: In the stable coronary patients of the ASIS trial, we found that T-wave alternans magnitude nearly tripled from 0.27 ± 0.02 mV × ms before ischemia onset to 0.77 ± 0.08 mV × ms (P 2 mm and the ischemia-induced increase in T-wave alternans. Conclusions: We conclude that T-wave alternans often occurs in association with ambulatory ischemia. Thus, risk assessment in stable coronary patients may be enhanced by monitoring both ST segment deviation and T-wave alternans as they measure relevant but fundamentally different electrophysiological properties.