811-2 Evidence that Myocardial Stunning Occurs in Humans Following Unstable Angina

Reversible postischemic dysfunction, or myocardial stunning, is a well defined experimental entity which is characterized by the presence of a perfusion-contraction mismatch, i.e. the persistence of segmental dysfunction despite complete restoration of nutritive perfusion. Reversible dysfunction occurs following ischemic syndromes such as non-Q wave infarction, unstable angina, cardio-pulmonary bypass. Definite demonstration that reversible dysfunction indeed represents myocardial stunning is lacking, owing to the difficulty of measuring myocardial blood flow (MBF) in absolute terms. Therefore, we measured regional wall motion (by 2D echo) and absolute MBF with 13N-ammonia and positron emission tomography (PET) in 11 patients with unstable angina, Despite successful PTCA of the culprit lesion on the left anterior descending coronary artery, all patients showed persistent anterior. wall dysfunction at the time of the PET study (within 48 hours after PTCA). As judged from the changes in segmental wall motion (in 6±2 abnormal segments, mean±sd, out of 16 in each patient) from the time of PET study to 4–8 weeks later, regional dysfunction was entirely reversible in 9/11 patients. In these 9 patients, the segmental wall motion score improved from 2.4±0.3 to 1.2±0.1 at late follow-up. With PET, 13N-ammonia MBF was within the normal range in 8/9 patients (95±21ml/min/l00 g, range 60124ml/min/l 00 g), while it was decreased (33ml/min/l00 g) in the remaining patient. On average, in the 9 patients, absolute MBF was similar among stunned and remote normally contracting myocardial segments (88±28 vs 85±25ml/min/100 g, p=ns). Our data thus show perfusion-contraction mismatch, confirming that myocardial stunning can occur in humans following attacks of unstable angina