Response to exercise early after uncomplicated acute myocardial infarction in patients receiving no medication: long-term follow-up

Cardiovascular function and prognosis have not been adequately defined early after an uncomplicated acute myocardial infarction in patients given no medication. Ninety such patients were studied with treadmill testing submaximally at 3 weeks and maximally at 8 weeks after infarction. The exercise heart rate, rate-pressure product and oxygen uptake were, respectively, 120 ± 17 beats/min, 179 ± 43 and 17.4 ± 1.0 ml/kg per min at 3 weeks and 157 ± 20, 271 ± 55 and 24.3 ± 3.7 at 8 weeks. Exercise variables at submaximal equivalent exercise work did not change from 3 to 8 weeks. At maximal exercise 15.6 percent of patients had S-T changes alone, 8.9 percent had angina alone and 12.2 percent had both. Patients were followed up for a mean of 23.7 months for complications—death, reinfarction, bypass grafting and progression to functional class III and IV. Complications occurred in 27 percent of patients with both angina and S-T changes, 29 percent of those with S-T changes alone, 25 percent of those with angina alone, 8 percent of those with ventricular arrhythmia alone, 12 percent of those with a normal 8 week treadmill test and in 17 percent of the group as a whole. Another 18 patients who were given no medication and whose course was uncomplicated could not perform a maximal 8 week treadmill test because of angina pectoris or S-T segment depression, or both, and 56 percent of these had long-term complications.In conclusion, these reference values serve as safe limits in performing treadmill testing early after acute myocardial infarction. S-T changes or angina, or both, and inability to complete a maximal 8 week treadmill test identify patients at risk for later complications even though these patients may have been considered to be in a low risk category clinically.