Early and late exercise capacity after acute myocardial infarction treated with recombinant tissue-plasminogen activator

Thrombolytic therapy salvages jeopardized myocardium and preservesleft ventricular function. Therefore, a beneficial effect onexercise tolerance and haemodynamic adaptation to exercise canbe anticipated. In the present study the results of bicycleexercise tests, performed at 10 to 14 days and at more than1 year after infarction, were compared between patients randomizeddouble blindly to recombinant tissue plasminogen activator (rt-PA)or placebo. At 2 weeks, the maximal heart rate (140 vs 130 beats.min^–1 P=0.017), systolic blood pressure (169 vs 161 mmHg,P=0.018) and pressure-rate product (22907 vs 20865 beats. min^-1mmHg,P=0.0025) were higher in rt-PA treated patients (n=145) thanin controls (n=142). At a mean follow-up of 16 months, rt-PApatients (n=126) performed a higher total and peak work load(733 vs 600 Watts. min, P=0.027 and 133 vs 100 Watts, P=-0.036,respectively) than control patients (n=122). During both exercisetests the incidence of clinical or electrocardiographic signsof ischaemia was similar. Multiple regression analysis indicatedthat age and end-systolic volume were predictors of peak pressure-rateproduct at 2 weeks (R²=0.11, P=0.0001). Age, sex and left ventricularejection fraction at discharge were independent predictors ofpeak work load at 2 weeks (R²=0.32, P=0.0001) and the squareroot of peak work load at 16 months (R²=0.39, P=0.001). Thesefindings suggest that an improved left ventricular functionin the thrombolysis group plays a role in the better exercisecapacity observed in rt-PA treated patients.