Thallium-201 exercise myocardial imaging to evaluate myocardial perfusion after coronary artery bypass surgery.

Abstract

SUMMARY To assess the usefulness of thallium-201 exercise scintigraphy in evaluating myocardial perfusion after coronary artery bypass surgery imaging was performed after submaximal bicycle ergometry and at rest in 54 patients before and within 24±10 (SD) weeks after operation. According to the postoperative scintigram the patients were assigned to three groups. Group 1 comprised 31 patients whose perfusion returned to normal after exercise and at rest within the preoperatively ischaemic regions; group 2 comprised 16 patients with identical pre-and postoperative exercise-induced perfusion defects, and group 3 comprised seven patients with enlarged or new perfusion defects postoperatively.Clinically, 14 of 31 patients in group 1 were symptom free after operation, two of whom, however, showed an abnormal exercise electrocardiogram; whereas the other 17 patients still complained of chest pain and in six of them the exercise electrocardiogram was also pathological. In group 2 eight of 16 patients were symptom free after operation and showed normal exercise electrocardiograms and the other eight continued to suffer from angina, and seven had a pathological exercise electrocardiogram. All seven patients in group 3 were symptomatic and showed an abnormal exercise electrocardiogram. Thus, scintigraphy identified eight of 20 patients (40%) who were symptom free and showed normal exercise electrocardiograms as still having exercise-induced ischaemia and thus as having not truly benefited from the surgical intervention. In contrast, improvement in perfusion was documented in 17 of 31 patients (53%) despite further complaints of chest pain and persistence of a pathological exercise electrocardiogram in six of them.Bypass graft patency rate paralleled the scintigraphic findings in the 35 patients who were restudied arteriographically. In group 1 (16 patients restudied) the graft patency rate was 81 per cent, significantly different from the 38 per cent in group 2 (13 patients restudied), and it was only 15 per cent in group 3 (six patients restudied). Similarly, the degree of vascular obstruction had decreased in group 1 from a score of 2 1 ±0 3 (SEM) preoperatively to a score of 1 1 ±0O3 postoperatively, remained unchanged in group 2, averaging 3± 0±04 score values preoperatively and 3-1±0-5 score values postoperatively, and even tended to increase in group 3 from 2-2 ±06 score values preoperatively to 3-3± 0-6 score values postoperatively.It is concluded that thallium-201 exercise scintigraphy is a useful technique to document changes in regional perfusion after surgery and is definitely superior to the clinical evaluation of patients including the exercise electrocardiogram.More than 10 years have elapsed since coronary management of coronary heart disease as a new artery bypass surgery was introduced into the therapeutic principle.