Study objectives: To investigate the nature and extent of the alteration in autonomic function following heterotopic lung transplantation.
Design: Measures of cardiac parasympathetic nervous system activity (PNSA) and systemic sympathetic nervous system activity (SNSA) were compared in lung transplant patients and age-matched healthy subjects, both at rest and following autonomic perturbation.
Setting: Lung transplantation service of a university teaching hospital.
Patients and participants: Twenty-two lung transplant patients (mean [± SEM] age, 50.5 ± 2.4 years) and 13 healthy subjects (mean age, 48.2 ± 3.7 years).
Measurements and results: Lung transplant patients had decreased baseline time and frequency domain measures of heart rate variability compared to healthy subjects (root mean square of successive differences in R-R intervals, 11.2 ± 1.1 vs 30.3 ± 4.5 ms, respectively [p < 0.005]; LnHP, 2.4 ± 0.2 vs 4.8 ± 0.4 ms2, respectively [p < 0.005]). In addition, lung transplant patients demonstrated an attenuated reduction in LnHP/LnTP following head-up tilt in comparison to healthy subjects (p < 0.05). The baseline recumbent plasma norepinephrine level was increased in lung transplant patients compared to healthy subjects (3.25 ± 0.43 vs 2.00 ± 0.27 nmol/L, respectively; p < 0.05), and levels increased in both groups with upright head-up tilt. There were no differences between the two groups in heart rate or mean systolic BP responses to both the Valsalva maneuver and cold pressor testing.
Conclusions: Lung transplant patients have both reduced PNSA and increased SNSA at rest. Furthermore, these patients appear to have a preserved capacity to respond to autonomic perturbation by increasing SNSA. The mechanisms underlying these observations and their prognostic implications remain to be determined.