[Diagnostic value of changes in Q wave amplitude in left thoracic leads during physical loading]

The informative value of stress-induced changes in Q wave amplitude and ST segment for the diagnosis of coronary heart disease was compared in records from left chest leads. Bicycle ergometry was conducted in 74 patients with coronary angiographically documented stenosis (more than 70% of the lumen) of one or more coronary arteries, and 28 subjects showing no apparent coronary arterial changes. The lack of increment in Q wave amplitude was shown to be a fairly sensitive sign of myocardial ischemia. Yet, its specificity is relatively low, much inferior to that of ST changes. The predictive value of changes in ST segment is significantly higher, as compared to that of changes in Q wave amplitude during exercise. Simultaneous assessment of ST and Q wave changes in response to stress failed to improve the predictive accuracy, as compared to the interpretation of ST changes alone.