Symptom-limited versus low level exercise testing before hospital discharge after myocardial infarction

Abstract

Objective. This study was undertaken to compare a low level and a symptom-limited test performed before hospital discharge after an uncomplicated myocardial infarction.Background. Exercise testing after myocardial infarction provides useful prognostic information. Usually either a low level test is performed before hospital discharge or a symptom-limited test is performed at 3 weeks.Methods. The study group comprised 202 patients with an uncomplicated myocardial infarction; 58 patients had a non-Q wave infarction and 115 patients had received thrombolytic therapy. Both a low level and a symptom-limited exercise test were performed in 200 of the 202 study patients in randomized order on consecutive days, a mean of 7.4 ± 2.3 days after infarction.Results. The symptom-limited test required a considerably greater effort than the low level test: exercise duration was 554 ± 209 versus 389 ± 125 s (p < 0.0001), and peak work load was 5.7 ± 1.8 versus 4.2 ± 1.1 METs (p < 0.0001). The peak heart rate was higher during the symptom-limited test (121 ± 20 vs. 108 ± 14 beats/min, p < 0.0001), as was the rate-pressure product. The number of patients who developed ST segment depression ⩾ 1 mm increased from 56 during the low level test to 89 during the symptom-limited test (p < 0.0001). ST segment depression ⩾ 2 mm occurred in 22 patients during the low level test and in 41 patients during the symptom-limited test, an 86% increase (p < 0.0001). The number of patients with either angina or ST depression ⩾ 1 mm increased from 66 to 105 (p < 0.0001) with the symptom-limited test. Exercise test results were similar for patients with a Q wave or a non-Q wave infarction. Exercise duration was longer and exercise-induced ST depression less frequent in patients who had received thrombolytic therapy.Conclusions. A symptom-limited exercise test performed before hospital discharge after uncomplicated myocardial infarction provides a significantly greater cardiovascular stress than does a low level test and is associated with aa ischemic response nearly twice as frequently. The prognostic significance of a positive response at higher work loads bas not been defined.