Exercise-induced U-wave alterations as a marker of well-developed and well-functioning collateral vessels in patients with effort angina.

OBJECTIVES: We sought to determine whether exercise-induced U-wave alterations are observed in association with well-developed and well-functioning collateral vessels.
BACKGROUND: Although exercise-induced electrocardiographic (ECG) U-wave alterations including negative and prominent U waves have been established as a marker of significant or critical narrowing of a major coronary artery, the relation between this finding and the degree of collateral development has not yet been determined.
METHODS: Patients with stable effort angina were divided into two groups according to the presence (group A, n = 46) or absence (group B, n = 79) of exercise-induced either negative or prominent U waves in the precordial leads; the clinical profiles, coronary angiographic findings and also ischemic status during 60 s of coronary balloon occlusion were compared between the two groups.
RESULTS: The incidence of severe angina (CCS [Canadian Cardiovascular Society] class III or IV) was higher (p < 0.05) in group A (52%) than in group B (32%) patients. Good collateral vessels (Rentrop grade 2 or 3) into the perfusion territory of the culprit vessel were observed more frequently (p < 0.05) in group A (70%) than in group B (43%) patients. Coronary balloon angioplasty was carried out in 23 patients of group A and 40 patients of group B. Both ischemic ST changes (52% vs. 85%) and angina (57% vs. 80%) during balloon inflation were less (p < 0.05) frequently observed in group A than in group B. The incidence of no apparent myocardial ischemia with ST deviation or angina during the balloon inflation was higher (p < 0.05) in group A (39%) than in group B (10%) patients. In the prediction of the absence of myocardial ischemia during balloon inflation by the presence of exercise-induced U-wave alterations, the sensitivity was 69% (9/13) and the specificity was 72% (36/50) in the study patients.
CONCLUSIONS: Exercise-induced U-wave alterations are a marker for well-developed collateral circulation in patients with stable but severe effort angina. This finding is also highly predictive of the absence of myocardial ischemia during transient coronary balloon occlusion and possibly of low-risk for development of acute myocardial infarction or hemodynamic instability upon abrupt closure of the culprit coronary artery.