Electrocardiographic mapping after exercise for evaluation of coronary bypass graft surgery

Electrocardiographic mapping after exercise adds an extra dimension to the routine exercise test because a measure can be made of the area and severity of electrocardiographic changes that occur after exercise. The value of this technique in assessing coronary bypass graft surgery was investigated in 50 patients who had postoperative coronary angiography after undergoing such surgery. The patients were classified into three groups: The 35 patients in Group 1 were free of pain at follow-up and had no new precordial Q waves. Among these, 24 patients had patent grafts and no precordial area of S-T segment change after exercise. The remaining 11 patients had areas of exercise-induced S-T segment change postoperatively; 10 of the 11 had at least one blocked graft and 1 had a patent although poorly functioning graft. The 10 patients in Group 2 continued to have chest pain after operation. Eight of the 10 had an area of S-T segment change that persisted after exercise and at least one blocked graft; the 2 patients without precordial S-T segment changes after exercise had patent grafts. The five patients in Group 3 were in poorer condition after operation; three had greater areas of S-T segment change after exercise, and the remaining two had new areas of Q waves. All patients had at least one occluded graft.

In 8 (16 percent) of the 50 patients studied before operation precordial areas of S-T segment change after exercise that were identified with electrocardiographic mapping were not identified using a modified 12 lead system. After operation, mapping revealed precordial areas of ischemia in 24 patients; In 4 (17 percent). These areas were not detected with the modified 12 lead electrocardiogram. Electrocardiographic mapping after exercise is a simple noninvasive test that objectively describes the effects of coronary bypass surgery on myocardial ischemia and aids in interpretation of a patient's report of a change in the frequency of angina. Because it provides more information than a modified 12 lead system it may reduce the need for postoperative angiocardiography.