[Evaluation of aortocoronary bypass using exercise myocardial thallium 201 scintigraphy]

The surveillance of aortocoronary bypass grafts is a difficult problem. Clinical examination and exercise testing are unable to give a complete evaluation of the operative results and cardiac catheterisation with radiological opacification of the grafts are not without risk and cannot be repeated periodically. Therefore, radioisotopic methods have been proposed as a means of assessing aortocoronary bypass grafts. The aim of this study was to evaluate postoperative myocardial perfusion by Thallium 201 scintigraphy. The authors compared pre and postoperative scintigraphies in 37 patients undergoing aortocoronary bypass surgery (36 men and 1 woman, average age: 53.9 years). Preoperative coronary angiography showed 9 cases of single vessel disease, 11 cases of double vessel diseases and 17 cases of triple vessel disease. Seventy one bypass grafts were performed (average 1.92 grafts/patient): 37 on the LAD, 15 on the circumflex, 10 on the diagonal and 9 on the right coronary. All patients were submitted to the same protocol before surgery and during the third postoperative month; Clinical examination, ECG, exercise stress testing and Thallium 201 myocardial scintigraphy. The results confirm the improvement in myocardial perfusion after coronary bypass surgery. The percentage of pathological scintigraphic segments fell from 42 per cent before surgery to 27 per cent after surgery (p less than 0.01). The total Thallium perfusion index improved significantly after surgery from 9.3 +/- 2 to 7.7 +/- 1.9 (p less than 0.01). Thallium 201 scintigraphy was superior to clinical examination and exercise testing in the assessment of graft patency, identifying 2 postoperative infarctions inapparent on clinical examination, excluding postoperative non-anginal chest pain and evaluating myocardial perfusion in patients who had sub maximal postoperative exercise stress tests. The relatively non traumatic character of Thallium 201 scintigraphy makes it the best non-invasive method of assessing aortocoronary bypass graft patency.