Differential Characteristics of Neural Circulatory Control

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Abstract
Background Reappearance of low-frequency (LF) (±0.10 Hz) oscillations in RR interval (RR) after cardiac transplantation is indicative of sympathetic efferent reinnervation. We hypothesized that restored LF oscillations in RR in heart transplant recipients (HTRs) are linked to oscillations in muscle sympathetic nerve traffic (MSNA). Methods and Results RR, RR variability, and MSNA were recorded 5±2 months (n=7, short-term HTRs) and 138±8 months (n=7, long-term HTRs) after heart transplantation and compared with matched hypertensive patients (n=7). A coherence function determined the coupling between LF oscillations in MSNA and RR. RR variance did not differ between short-term and long-term HTRs. However, LF variability was only 1±0.5 ms 2 in the short-term HTRs but was 15±8 ms 2 in the long-term HTRs ( P P P P P Conclusions Cardiac reinnervation after long-term heart transplantation is characterized by a restoration of the coherence between LF oscillations in RR and MSNA. Higher MSNA in long-term than in short-term HTRs suggests that time elapsed after cardiac transplantation may be a major determinant of sympathetic excitation in heart transplant recipients.