Arrhythmogenic potential of exercise-induced myocardial ischaemia.

In a series of 300 patients following transmural infarction undergoing coronary angiography because of ischaemia in the surviving myocardium, 17 demonstrated an exercise response indicative of myocardial ischaemia in the absence of angina pectoris. The presence of ischaemia in the region of the myocardium under scrutiny was proven by: (1) ST-segment depression during bicycle-ergometry of at least 2 mm in leads without any QRS or ST-T changes at rest. (2) greater than 75% stenosis of vessels supplying the area under investigation, in addition to the vessel supplying the region of the infarction. (3) A reversible Thallium-perfusion defect on exercise. We compared those 17 patients with silent myocardial ischaemia with 21 patients with typical angina pectoris on exertion. All patients underwent 24-hour Holter monitoring, treadmill exercise testing at a target heart rate previously determined as inducing signs of myocardial ischaemia, and swimming and calisthenic programs with telemetric ECG recording. There was no close relationship between myocardial ischaemia and the occurrence of complex ventricular arrhythmias. In silent ischaemia complex ventricular arrhythmias do not occur at a higher rate than in patients with angina pectoris.