PACING-INDUCED ST SEGMENT DEVIATION IN PATIENTS WITH UNSTABLE ANGINA - CLINICAL, ANGIOGRAPHIC, AND HEMODYNAMIC CORRELATION

To assess the clinical, coronary arteriographic, and hemodynamic diffe rences between the unstable angina patients manifesting ST segment dep ression and those showing ST segment elevation as well as those demons trating chest pain only without ST segment deviation during pacing, lo w-dose digital subtraction ventriculography was performed in 33 patien ts before and after abrupt cessation of atrial pacing during selective coronary arteriography. Transient ST segment depression during pacing was observed in 17 patients (52%), whereas 6 patients (18%) showed ST segment elevation; however, 10 patients (30%) did not manifest any ST segment deviation in spite of typical chest pain. Hypertension and a history of myocardial infarction were observed in a significantly high er (P < 0.05) proportion of patients with ST segment depression than i n those with ST elevation. Patients who manifested ST segment depressi on during pacing had a higher incidence of triple-vessel disease (65 v s 17%; P < 0.05) as compared with the patients with ST segment elevati on. Indirect evidence of intracoronary thrombi (complicated lesion, ab rupt occlusion, and intraluminal filling defect) was noticed in a high er frequency (P < 0.05) in the group of patients with ST elevation dur ing pacing. In patients with ST segment depression, no significant cha nges of global left ventricular (LV) functional parameters were observ ed. However, the length of the LV severe hypokinetic region was increa sed significantly (6.2 +/- 3.1 vs 23.5 +/- 6.2%; P < 0.05) during paci ng in this group of patients. The shortening of the affected segments of the left ventricle was decreased significantly (52.3 +/- 3.6 vs 38. 3 +/- 4.9%; P < 0.05) in these patients during pacing. In the group of patients with ST segment elevation during pacing, decrease in ejectio n fraction was associated with significant (P < 0.01) increase in midw all equatorial diastolic stress as compared with the patients with pac ing-induced ST segment depression as well as patients without ST segme nt deviation. In the group of patients without ST segment deviation du ring pacing there was no considerable aggravation of LV global or regi onal function. This distinction should be taken into consideration in evaluating patients with unstable angina for diagnostic and therapeuti c intervention.