RELATION BETWEEN DIASTOLIC PERFUSION TIME AND CORONARY-ARTERY STENOSIS DURING STRESS-INDUCED MYOCARDIAL-ISCHEMIA

Background Experimental studies have demonstrated that during stress-i nduced myocardial ischemia, coronary obstruction and diastolic perfusi on time are factors that limit subendocardial perfusion and correlate to degree of myocardial dysfunction. The relation between these two fa ctors has not yet been investigated in humans. The aim of the present study was to assess the relation between diastolic perfusion time and degree of coronary stenosis during different types of stress tests. Me thods and Results Nine patients with isolated and proximal stenosis of the left anterior descending coronary artery were selected. Patients underwent three different randomized stress tests (upright, supine bic ycle stress test, and transesophageal atrial pacing). Diastolic perfus ion time, heart rate (RR interval), and systolic and diastolic pressur es were measured during the test and at the ischemic threshold (0.1-mV ST-segment depression). Angiographic measurements of coronary stenosi s were evaluated by quantitative coronary angiography. At the ischemic threshold, significant differences among tests were found in heart ra te (P<.05), systolic pressure (P<.001), and diastolic pressure (P<.05) . In each stress test, diastolic perfusion time at the ischemic thresh old was closely correlated with minimal stenosis diameter (r=.97; P<.0 01) and percent diameter stenosis (r=.92; P<.001) with no difference a mong the tests. In contrast, heart rate, rate-pressure product, and ti me to ischemic threshold were not significantly correlated with percen t diameter stenosis and minimal stenosis diameter. No significant corr elation was observed at the ischemic threshold between diastolic perfu sion time and corresponding values of heart rate, despite the close co rrelation at rest (r=.95; P<.001). Conclusions Despite differences in associated hemodynamic responses to various stress tests, a close rela tion exists between stenosis severity and diastolic perfusion time at the onset of stress-induced myocardial ischemia. Therefore, diastolic perfusion time at the ischemic threshold may be an indirect estimate o f the hemodynamic significance of coronary stenosis.