EVIDENCE FOR A CENTRAL ORIGIN OF THE LOW-FREQUENCY OSCILLATION IN RR-INTERVAL VARIABILITY

Background-Short-term variability of RR interval and blood pressure oc curs predominantly at low frequency (LF; approximate to 0.1 Hz) and hi gh frequency (approximate to 0.25 Hz). The arterial baroreflex is thou ght to be the predominant determinant of the LF component of RR variab ility. Patients with severe congestive heart failure (CHF) have an att enuated or absent LF oscillation in RR variability. The left ventricul ar assist device (LVAD) offers a unique possibility for analysis of sp ectral oscillations in RR interval independent of any effects of blood pressure that influence these oscillations via the baroreflex. Method s and Results-We performed spectral analysis of RR, blood pressure, an d respiration in 2 patients with CHF before and after LVAD implantatio n. LF components of the RR-interval and blood pressure variability wer e absent in both CHF patients before LVAD implantation. After LVAD imp lantation, spectral analysis of the RR interval showed restoration of a clear and predominant LF oscillation in the native hearts of both pa tients, with no such oscillation evident in the blood pressure profile . Conclusions-During total circulatory support with the LVAD, the LF o scillation In RR interval of the native heart, absent in CHF, is resto red. This LF oscillation in RR interval occurs in the absence of LF os cillations in blood pressure and thus is unlikely to be explained by b aroreflex mechanisms. Hence, the absence of LF oscillation in the RR i nterval in CHF is functional and is reversible by LVAD circulation. Th e presence of a predominant LF oscillation in RR interval independent of any oscillation in blood pressure suggests that the LF oscillation is a fundamental properly of central autonomic outflow.