Assessment of blood pressure variability by means of spectral and symbolic analysis in normal and congestive heart failure rats

Abstract

Neural control of circulation is altered in congestive heart failure (CHF), as assessed by heart rate variability. Viceversa, few data are available regarding arterial pressure variability (APV). We evaluated neural control of AP in normal and CHF rats using linear, i.e. spectral (PSA), and nonlinear, i.e. symbolic analysis (SA) of APV. While PSA of APV detects the two rhythmic components related to sympathetic and vagal modulations, the low-frequency (LF) and the high-frequency (HF) oscillations, SA decomposes APV series in patterns of 3 beats and classifies into 3 categories: OV (sympathetic modulation), 1V and 2V (vagal modulation). Experiments were carried out in 7 normal and 6 CHF rats. CHF was induced by coronary artery ligation and was assessed by echocardiography. Recordings of heart rate and AP were performed 4 weeks after surgery. Systolic and diastolic AP were similar in the two groups, as well as total variance of APV. PSA profile showed, in CHF, a significantly faster respiratory rate, as derived from the center frequency of the HF component, and a smaller normalized LF. On the other hand, SA revealed a significantly lower 0V pattern and a higher 2V pattern in CHF. Our data indicate that APV in CHF rats is characterized by an increased respiratory and a decreased sympathetic vasomotor modulation, in spite of the well-known neurohumoral activation. Supported by a FIRST grant from U of Milan and a NHLBI RO1 HL-63915