Improvement in exercise performance after unsuccessful myocardial revascularization

Abstract

To assess the status of patients with all grafts occluded after aortocoronary bypass surgery, the clinical, angiographic and exercise testing data of all patients within the Seattle Heart Watch who had no patent grafts at follow-up angiography were analyzed. From this subset 23 patients with complete pre- and postoperative evaluations were found. Postoperatively, 12 of 23 patients (52 percent) related improvement of at least one functional class, and 5 were asymptomatic. Comparison of pre- and postoperative exercise performance revealed a mean increase in exercise duration, maximal pressure-rate product and maximal heart rate, but only the latter increase was statistically significant. Analysis of the individual data revealed significant postoperative improvement in exercise capacity in 13 patients (57 percent); and in maximal pressure-rate product in 9 patients (39 percent); 5 of 13 patients with an ischemic S-T response preoperatively no longer had this response postoperatively. Neither preoperative ejection fraction, number of vessels diseased, number of grafts attempted, interval to follow-up study, deterioration in the native coronary circulation, appearance of collateral circulation, control of risk factors nor medical therapy appeared to separate the patients who did and did not show improvement. However, 11 patients (48 percent) demonstrated angiographic or clinical evidence, or both, of interim myocardial infarction. This group manifested a mean increase in exercise duration, maximal pressure-rate product and maximal heart rate postoperatively. It appears that improvement after unsuccessful myocardial revascularization is not uncommon and that in some, but not all cases, the improvement is related to myocardial infarction. Increased myocardial blood flow is not the only mechanism of subjective and objective clinical improvement after aortocoronary bypass surgery.