Ischemia-induced changes of the signal-averaged electrocardiogram: Experimental investigation during percutaneous transluminal coronary angioplasty balloon-occluded coronary artery

Introduction: The influence of myocardial ischemia on the detection of an a rrhythmogenic substrate with the signal-averaged ECG is unclear. Methods and Results: In 80 patients with single vessel coronary artery dise ase and a critical stenosis of the left anterior descending vessel selected after coronary angiography in whom percutaneous transluminal coronary angi oplasty (PTCA) was planned, we retrospectively investigated the signal-aver aged ECGs in the time domain before, during, and after occlusion of the cor onary artery by the PTCA balloon. Forty patients were resuscitated from ven tricular fibrillation (VF group), and 40 patients had no ventricular arrhyt hmia (non-VF group). Late potentials were seen at rest in 26 of 40 patients in the VF group, During ischemia, the duration of the filtered QRS complex and the duration of low-amplitude signals < 40 mu V increased significantl y. In another 14 patients in the VF group, late potentials were observed on ly during ischemia, In 4 of 26 patients in the VF group without prior infar ction but with severe ischemia present at rest, successful PTCA eliminated preexistent late potentials. In the non-VF group, one patient had late pote ntials present at rest. In two patients with prior infarction, late potenti als were provokable only during transmural ischemia, Conclusion: Myocardial ischemia is able to modify detection of an arrhythmo genic substrate with the signal-averaged EGG.