DIFFERENT MECHANISMS OF ISCHEMIC ADAPTATION TO REPEATED CORONARY-OCCLUSION IN PATIENTS WITH AND WITHOUT RECRUITABLE COLLATERAL CIRCULATION

Objectives. The aim of this study was to investigate the interaction b etween ischemic preconditioning (IF) and collateral recruitment (CR) d uring ischemic adaptation in patients. Background. The mechanism of is chemic adaptation still remains controversial in humans. Methods. The clinical, electrocardiographic, hemodynamic and echocardiographic resp onses to three 150-s occlusions of the left anterior descending corona ry artery were assessed in relation to CR in 18 patients with effort a ngina undergoing elective percutaneous transluminal coronary angioplas ty. Results. During the first occlusion, recruitable collateral circul ation (RCC) to the occluded myocardium was detected by myocardial cont rast echocardiography in 6 patients (Group C) and was not seen in 12 ( Group N). In Group N, all patients manifested signs of severe ischemia during each inflation. However, their symptoms and ST segment shift s ignificantly decreased from the first to the third occlusions, suggest ing the occurrence of IP. The elevation of mean pulmonary artery press ure and deterioration of anterior wall motion were comparable between the first and the third occlusions in Group N. In contrast, myocardial ischemia was significantly less marked during occlusion in Group C th an in Group N, and no preconditioning effect was observed, The extent of RCC did not differ between the first and the third occlusions in ea ch group. Conclusions. Both IP and CR may play independent roles in is chemic adaptation in humans. With RCC, myocardial ischemia was greatly reduced. Without RCC, preconditioning clinically and electrocardiogra phically lessened myocardial ischemia but failed to preserve left vent ricular function. (C) 1997 by the American College of Cardiology.