Abstract
Bilateral lung transplantation (BLT) implies full lung denervation. It is an excellent model of cardiovascular regulation without modulation of heart activity by lung afferents. The high frequency (HF) peak of heart rate variability (HRV) is synchronous with breathing frequency (BF). If this comes from neural modulation of the heart beat by BF, HF of HRV should disappear after BLT. The aim of this study was to analyse HRV in BLT as compared with healthy controls (C).
11 BLT (6 women and 5 men), aged 49.0±14.5 yrs and 11 sex- and age-matched healthy controls (C), aged 47.3±14.5, were studied. We recorded heart rate (HR, ECG), blood pressure (Portapres) and BF (ultrasonic device) during 10 min of free breathing at rest, 10 min of cadenced breathing (0.25Hz) at rest, and 5min of handgrip, in supine posture. We evaluated spontaneous variability of HR, and of systolic, diastolic and mean pressure (SAP, DAP and MAP), by power spectral analysis, and baroreflex sensitivity (BRS), by the sequence method.
BLT had higher HR, but the same SAP, DAP and MAP than C. BF was higher in BLT than in C during free breathing. BLT showed lower BRS, total power (PTOT), low-frequency peak (LF) and HF than C, in all conditions. The LF/HF ratio was higher in BLT than in C. In normalised units, BLT had higher LF (LFnu) and lower HF (HFnu) than C. Concerning blood pressure, BLT had higher PTOT, LF and HF powers for SAP; higher HF and lower LF/HF for DAP; lower LF/HF for MAP, than C.
HRV was reduced in BLT. A higher LF/HF ratio implies that the PTOT drop was mostly due to HF. The reverse was the case for SAP. The results are compatible with the hypothesis that neural modulation from lung afferents contributes to the HF component of HRV.
- Copyright ©the authors 2016