Can prolonged exercise-induced myocardial ischaemia be innocuous?

Abstract

AIMS: To evaluate the innocuousness of intense and prolonged exercise training above the threshold for myocardial ischaemia (1 mm ST-segment depression). METHODS AND RESULTS: Twenty-two patients with ischaemic heart disease (IHD) were randomized to exercise training either at a target intensity that induced myocardial ischaemia (ischaemic group) or that adhered to current guidelines (control group). Training was progressively increased to 60 min under continuous electrocardiographic (ECG) monitoring. Cardiac troponin T (cTnT) was measured at various intervals. Ambulatory ECG monitoring was performed before and after 6 weeks of training and left ventricular function was evaluated in the ischaemic group after at least 6 weeks of training. The ischaemic group had myocardial ischaemia during the first 20, 40, and 60 min exercise sessions for 12.3 +/- 6.8, 29.0 +/- 12.9, and 49.8 +/- 2.2 min, respectively, with ST-segment depression ranging from 1.0 to 2.1 mm. No patient in either group demonstrated significant arrhythmias or increased cTnT. The ischaemic group had preserved left ventricular function. CONCLUSION: In patients with IHD, prolonged and repeated ischaemic training sessions up to 60 min can be well tolerated without evidence of myocardial injury, significant arrhythmias, or left ventricular dysfunction.