Superiority of selected treadmill exercise protocols predischarge and six weeks postinfarction for detecting ischemic abnormalities.

We evaluated 29 uncomplicated post-myocardial infarction patients with heart rate-limited and symptom-limited modified Naughton treadmill exercise tests predischarge and 31 similar patients with symptom-limited modified Naughton and standard Bruce stress tests at 6 weeks following infarction to determine their comparative value for detecting unsuspected ischemic abnormalities. Predischarge, the symptom-limited modified Naughton test identified a significantly greater number of patients with ECG ST segment depression or angina than did the heart rate-limited test (21 vs 13 patients, p less than 0.05). This resulted from a significantly longer average maximal exercise duration (10.5 +/- 4.9 vs 7.9 +/- 4.2 minutes, P less than 0.001) and higher maximal rate-pressure product (21.9 +/- 5.8 vs 19.2 +/- 4.6 X 10(3), p less than 0.001) during the symptom-limited test. At 6 weeks following infarction, the standard Bruce stress test identified a significantly higher frequency of ischemic abnormalities than did the symptom-limited modified Naughton test (20 vs 13 patients, p less than 0.05). This resulted from a higher average maximal rate-pressure product (23.1 +/- 7.3 vs 21.0 +/- 6.2 X 10(3), p less than 0.02), despite a shorter maximal exercise duration (6.9 +/- 1.2 vs 10.7 +/- 4.4 minutes, p less than 0.001) during the Bruce stress test. We conclude that: (1) symptom-limited exercise is superior to heart rate-limited exercise predischarge and (2) the standard Bruce stress test is superior to the symptom-limited modified Naughton exercise test at 6 weeks following infarction for the detection of unsuspected ischemic abnormalities in uncomplicated postinfarction patients.