Stress echocardiography for assessing myocardial ischaemia and viable myocardium.

The electrocardiographic (ECG) ST segment response to exercise is perhaps the most commonly used functional test for the assessment of coronary artery disease.' However, it has important limitations in the evaluation of myocardial ischaemia for two reasons. First, according to the theory of the ischaemic cascade, ECG changes and symptoms are preceded by flow heterogeneity followed by the development of regional myocardial dysftmction.2 Thus, unless the patient exercises to the level at which ECG changes occur, demand driven myocardial ischaemia may not occur. Second, resting ECG abnormalities may render changes occurring during stress uninterpretable. Furthermore, the presence of systemic hypertension, even in absence of any resting ECG abnormalities, may result in a false positive diagnosis of coronary artery disease.3 In a recent study4 only 35% of 1814 consecutive patients referred for stress testing had an interpretable ECG and a successful maximal exercise. Echocardiography is currently the most widely used technique for the assessment of structure and function of the heart. Occurrence of abnormal regional systolic wall thickening during stress is perhaps the most specific sign of myocardial ischaemia. Echocardiography has been used during stress