Effect of 8-week exercise-based cardiac rehabilitation on cardiac autonomic function: A randomized controlled trial in myocardial infarction patients.
OBJECTIVE
The purpose of this study is to evaluate the effects of an 8-week exercise-based cardiac rehabilitation program on traditional and nonlinear heart rate variability (HRV) indexes, assessing the potential confounding influences of habitual physical activity (PA) and dietary intake.


METHODS
In this parallel-group trial, 96 patients (56 ± 10 years old) were randomized to the exercise group (EG) or to the control group (CG) 4 weeks after an acute myocardial infarction. Exercise-based cardiac rehabilitation program consisted of aerobic exercise at 70% to 85% of maximal heart rate for 3 sessions per week plus usual care. The CG received only usual care. The baseline and final assessments comprised resting short-term HRV (primary outcome) by a Polar R-R recorder under controlled breathing (12 breaths per minute), habitual PA by accelerometers, and dietary intake by a 4-day food diary.


RESULTS
Two patients in each group dropped out and were not included in the intention-to-treat analysis. In the remaining 92 patients (EG = 47 and CG = 45), at baseline, only a difference in the proportion of nitrate medication use was significant between groups. After 8 weeks, no significant changes were found between groups on traditional and nonlinear HRV indexes (eg, ln HF, EG from 5.7 ± 1.5 to 5.9 ± 1.3 and CG from 5.5 ± 1.6 to 5.5 ± 1.5), habitual PA, and dietary intake.


CONCLUSIONS
Eight weeks of exercise-based cardiac rehabilitation program is an insufficient stimulus to improve cardiac autonomic function in post-myocardial infarction patients under optimal medication and with high levels of traditional and nonlinear HRV indexes at baseline.
Research Center in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal. Electronic address: nloedfisica@gmail.com.
Nórton Luís
NL
Oliveira
Research Center in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal; School of Health Sciences, University of Aveiro, Aveiro, Portugal.
Fernando
F
Ribeiro
Cardiology Department, Centro Hospitalar de Gaia/Espinho, Vila Nova de Gaia, Portugal.
Madalena
M
Teixeira
Physical Medicine and Rehabilitation Department, Centro Hospitalar de Gaia/Espinho, Vila Nova de Gaia, Portugal.
Lilibeth
L
Campos
Research Center in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal.
Alberto Jorge
AJ
Alves
Research Center in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal.
Gustavo
G
Silva
Research Center in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto, Porto, Portugal.
José
J
Oliveira
D001341:Autonomic Nervous System / Q000503:physiopathology*; D004562:Electrocardiography; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology / Q000534:rehabilitation*; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome