Silent ischaemia in post-myocardial infarction patients submitted to physical training

Recently, more attention has been focused on the detection and treatment of silent myocardial ischaemia. Electrocardiographic signs of exercise-induced asymptomatic myocardial ischaemia are very common findings among survivors of acute myocardial infarction. From data of our population we found that silent exercise-induced ischaemia is present in 15-20% of all patients, and that about half of the patients with exercise-induced ST-segment depression were free of symptoms. Ergometric data at the ischaemic threshold are similar between asymptomatic and symptomatic patients while the presence of symptoms is more frequent in patients who were also symptomatic before the myocardial infarction. During the training period, the majority of the 'silent' patients remained asymptomatic, 23% developed effort angina, and 9% developed angina at rest. Training monitoring may be helpful in identifying the variability of symptoms. Physical training, in particular an intermittent programme, increased the work-load at which the ECG ischaemic signs appeared. Among the possible mechanisms responsible for exercise-induced silent ischaemia, a different pain tolerance and control of analgesia may be ascribed to explain the absence of pain, perhaps also determined by different endogenous beta-endorphin levels.