New Q waves after aortocoronary bypass surgery. Unmasking of an old infarction.

Abstract Review of records of 48 patients, who had had aortocoronary bypasses and preoperative and postoperative catheterizations, showed that 11 had new Q waves after operation. Seven of these had new infarctions immediately before or during operation as determined by evidence of deterioration on postoperative ventriculograms. Four cases had no deterioration, suggesting an alternative explanation for abnormal Q waves. These four patients with new Q waves, all in the inferior leads, had inferior-wall dysfunction before operation, with an inferior scar at surgery. After operation, anterior-wall function improved, without change inferiorly. These observations are consistent with unmasking of pre-existing infarction, rather than development of new infarction, and suggest that before operation, anterior ischemia electrically canceled inferior infarction. After operation, with relief of anterior ischemia by left-descending-coronary-artery bypass, anterior electrical force was augmented, and pre-existing inferi...