Effect of repetitive episodes of exercise induced myocardial ischaemia on left ventricular function in patients with chronic stable angina: evidence for cumulative stunning or ischaemic preconditioning?

Background-Myocardial stunning is known to occur following a single episode of effort angina in patients with coronary artery disease. The effect on l eft ventricular (LV) function of repeated episodes of ischaemia is unknown. Objectives-To investigate the effects of repeated episodes of exercise indu ced ischaemia on LV function in patients with chronic stable angina. Methods-Patients with significant coronary artery disease and normal LV fun ction underwent two episodes of symptom limited treadmill exercise separate d by three different time intervals: either 30 minutes (group A, n = 14); 6 0 minutes (group B, n = 14); or 240 minutes (group C, n = 14). Quantitative stress echocardiography was performed at repeated intervals between the tw o exercises and for 240 minutes following the second test. Results-For all groups there was no difference between the degree of ischae mia judged by maximal ST depression during the two tests. All episodes of e xercise induced ischaemia produced prolonged abnormalities of LV systolic a nd diastolic function despite rapid normalisation of haemodynamic and ECG c hanges. In group A (30 minutes) these abnormalities were less pronounced af ter the second test than after the first, while in group B (60 minutes) the y were more severe and long lasting. In group C (240 minutes) the two tests produced similar abnormalities of LV function. Conclusions-Prolonged abnormalities of LV function occurred following exerc ise induced ischaemia with a time course consistent with myocardial stunnin g. The severity and degree of LV dysfunction caused by a further episode of ischaemia appear to be dependent on the time interval between ischaemic ep isodes.