Regional distribution and timing of wall motion abnormalities during echo-dipyridamole stress test in patients with stable angina: the elusive link between coronary stenoses and myocardial ischemia.

BACKGROUND: Classic experimental studies have shown that in the presence of a flow-limiting coronary artery stenosis, myocardial ischemia during metabolic or pharmacological arteriolar vasodilation causes wall motion abnormalities, which precede electrocardiographic (ECG) changes in the myocardial regions supplied by the stenotic branch. The aim of this study was to establish whether in patients with chronic stable angina the regional distribution of wall motion changes and sequence of ischemic events are similar to that observed in experimental models, as currently believed. METHODS: The study population consisted of 20 men and 4 women (mean age 59 +/- 10 years) who were recruited on the basis of the following criteria: 1) a history of chronic stable angina without clinical and instrumental evidence of previous myocardial infarction; 2) reproducible positive exercise tests for ECG myocardial ischemia and anginal pain; 3) angiographically normal left ventricular function; 4) isolated stenosis of the left anterior descending coronary artery (LAD). Patients underwent continuous 12-lead ECG and echocardiographic monitoring during dipyridamole infusion. RESULTS: During dipyridamole infusion 3 patients (13%) did not develop echocardiographic changes, ECG changes or angina, 14 (58%) exhibited ECG changes, 18 (75%) lamented angina and 16 (67%) developed echocardiographic changes. In 5 of these 16 patients (31.5%) echocardiographic changes occurred in LAD-dependent territories only, in 5 they occurred in non-LAD-dependent territories only (31.5%) and in 6 (37%) they occurred in both LAD- and non-LAD-dependent territories. A total of 14 patients exhibited both echocardiographic and ECG changes and/or angina. In 6 of these 14 patients (43%) echocardiographic changes were the first ischemic events; in the remaining 8 patients (57%) ECG changes and/or angina were the first ischemic events. CONCLUSION: In the majority of patients during dipyridamole infusion regional wall motion changes occur in territories supplied by non-stenotic coronary artery branches; they are probably caused, therefore, by distal vessel dysfunction. Furthermore, the sequence of ischemic events is different in individual patients. These findings indicate that in stable angina the mechanisms of ischemia are multiple and that the link between coronary stenoses and myocardial ischemia is very elusive.