Randomized trial of a hospital-based exercise training program after acute myocardial infarction: cardiac autonomic effects.

Objectives: This study sought to determine whether a moderate intensity supervised exercise training program, performed immediately after an uncomplicated acute myocardial infarction, improves recovery in cardiac autonomic function compared with standard advice about activity at home.

Background: Exercise training has beneficial effects on cardiac autonomic function and may improve prognosis after acute myocardial infarction.

Methods: Thirty-nine male and 10 female patients, mean (+/-SE) age 57 +/- 1 years, with an uncomplicated acute myocardial infarction were randomized to either a 6-week moderate intensity supervised hospital-based exercise training program (exercise group) or to an unsupervised low intensity home walking program (control group). Outcome measures included changes in baroreflex sensitivity (phenylephrine bolus method) and heart rate variability (24-h Holter monitoring) and the endurance time at 85% of peak oxygen consumption.

Results: At baseline, there were no significant differences in left ventricular ejection fraction (57 +/- 2% vs. 53 +/- 2%), frequency of anterior infarction (27% vs. 18%) and peak creatine kinase (1,256 +/- 170 vs. 2,599 +/- 295 IU) between the exercise and control groups. Baroreflex sensitivity (10.5 +/- 1.0 vs. 8.4 +/- 1.2 ms/mm Hg) and time domain measures of heart rate variability were also similar. After completion of the program, the exercise group exercised for a median of 15 min (interquartile range 12 to 25) at a workload of 104 +/- 7 W compared with 7 min (interquartile range 3.5 to 12) at a workload of 89 +/- 8 W in the control group (p < 0.01). There were significant (p < 0.001) improvements in baroreflex sensitivity and heart rate variability for the 49 patients combined but no differences between the exercise and control groups. Baroreflex sensitivity improved by 3.4 +/- 1.0 and 1.7 +/- 1.0 ms/mm Hg and the standard deviation of 24-h RR intervals by 36 +/- 6 and 40 +/- 10 ms, respectively (p > 0.1).

Conclusions: A hospital-based exercise training program increased endurance capacity but did not improve recovery of cardiovascular antonomic function after uncomplicated acute myocardial infarction.