Exercise-induced inverted U wave in asymptomatic high-risk subjects. A preliminary study

The sixteen-lead ECG chest wall mapping was used to investigate the significance of inverted U waves during exercise in diagnosing occult coronary artery disease (CAD) in asymptomatic high-risk subjects. For this purpose 100 patients with various types of hyperlipidemia and 33 patients with diabetes mellitus were studied. None of these patients had a history of angina pectoris or myocardial infarction and all had normal resting ECG. Exercise was carried out on a bicycle ergometer to an end point, and ECG recordings were made from all sixteen chest leads. Inverted U waves developed during the early minutes of exercise in 8 patients (6 hyperlipidemics and 2 diabetics), indicating disease in 11 coronary artery territories (7 in the left anterior descending/diagonal coronary artery, 3 in the circumflex, and 1 in the right coronary artery territories). Subsequent coronary arteriography confirmed the territorial distribution of the inverted U waves in all the cases. Following coronary artery bypass grafting in 2 of these patients no U wave inversion developed during stress testing. It is concluded that exercise-induced inverted U wave is a reliable indicator of silent myocardial ischemia due to occult CAD in asymptomatic high-risk subjects. Its distribution on the ECG chest wall map is highly predictive of significant disease in the individual coronary artery territory. The disappearance of this ECG sign following myocardial revascularization is a further proof of its myocardial ischemic origin.