Objective: To investigate vagal parasympathetic functions by electromyographic R-R interval variation analyses in heart transplant recipients.
Design: Cross-sectional and longitudinal study.
Setting: Department of physical medicine and rehabilitation, university hospital.
Participants: Early (n=8; <3 mo) and late (n=17; >1 y) heart transplant recipients and healthy volunteers (n=20) were included.
Interventions: Not applicable.
Main outcome measures: The R-R interval variations at rest and in response to deep breathing, Valsalva, and tilt/standup maneuvers were analyzed in all patient and control groups. Further, 8 early heart transplant recipients were followed up at the sixth and twelfth months after transplantation.
Results: Compared with controls, both early and late transplant recipients had significantly lower R-R interval variation ratios (P<.05). There were no statistically significant differences between the early and late groups (P>.05). R-R interval variation ratios showed no significant changes from baseline (P>.025) in the early heart transplant recipients.
Conclusions: The findings of the study suggest that parasympathetic activities are suppressed in the early stage after heart transplantation and do not significantly recover with time. The electromyographic analysis of R-R interval variation is a simple test that may offer an attractive alternative for routine evaluation of autonomic dysfunction in heart transplant recipients.