T wave alternans and acute ischemia in patients undergoing angioplasty

Electrical T-wave alternans (TWA) has been recognized as a marker of electrical instability, and has been shown to be related with patients at increased risk for ventricular arrhythmias. In this paper we have studied the presence of TWA on 83 patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Two ECG recordings of each patient, a control recording before PTCA and the PTCA recording, were analyzed using a new robust TWA detector based on the GLRT for Laplacian noise distribution. 27 out of 83 patients (32.5%) showed TWA episodes, with highest prevalence on LAD artery occlusion subgroup (48.1%). In the study group, TWA appears always during the occlusion interval, generally after the first minute of occlusion, and its amplitude grows up as occlusion time increases. The lead profiles of the TWA and the alternant waveforms showed different distributions depending on the occluded artery. All these results suggest that TWA during angioplasty is related to the increasing electrical instability produced by the occlusion and that TWA in acute ischemia is a localized and transient phenomenon dependent on the occluded artery.