Respiratory-related blood pressure variability in patients after heart transplantation.

Our objective was to study whether the variations of blood pressure synchronous with respiration depend on the simultaneous changes of heart rate. Power spectral analysis of the heart period or R-R interval, blood pressure, and respiratory activity was performed by fast Fourier transform during 30 min of supine rest in 12 patients between 16 and 23 days after orthotopic heart transplantation and in 12 age- and sex-matched normal control subjects. The components of the variations of the R-R interval and blood pressure associated with respiration [high-frequency (HF) components] were derived from the power spectra. The HF component of the power spectrum of the R-R interval was almost absent in the transplanted patients compared with the control subjects (2.9 vs. 104 ms2; P < 0.001), whereas the HF component of the power spectrum of blood pressure was not significantly different between the two groups (1.72 vs. 1.65 mmHg2 for systolic and 0.35 vs. 0.60 mmHg2 for diastolic blood pressure). Respiratory variations of both systolic and diastolic blood pressure in humans can depend only slightly on the respiratory heart rate variations.