Simultaneous analysis of beat by beat systemic arterial pressure and heart rate variabilities in ambulatory patients.

The analysis of power spectral density (PSD) or RR variability in the electrocardiogram (ECG) has suggested that, in the early phase of essential hypertension, sympatho-vagal interaction is characterized by a sympathetic predominance. Recently, we have developed a high fidelity, direct arterial pressure ambulatory recording system which allows a beat by beat computer analysis of arterial pressure and heart rate. A microminiature tip transducer (Millar, diameter 0.8 mm) is inserted percutaneously into the radial artery and connected to a Holter two-channel magnetic tape recorder. The tip transducer has a wide band pass (> 1 kHz), excellent stability (congruent to 2 mmHg/24 h) and does not require a perfusion line. The overall frequency response of the entire recording-reproducing system is better than 20 Hz (-3 dB). The ECG and pressure signals are analysed with automatic autoregressive modelling algorithms to provide a quantitative estimate of blood pressure and heart rate variability through the computation of the PSD. In seven hypertensive patients, systolic arterial pressure and variance were higher during the day (157 +/- 9 mmHg and 122 +/- 9 mmHg2) than during the night (122 +/- 4 mmHg and 30 +/- 3 mmHg2). The PSD of RR and of systolic arterial pressure consisted of a predominant low frequency peak (congruent to 0.09 cycles/beat) during the day, and two peaks at low and high (congruent to 0.25 cycles/beat) frequency during the night. While RR variance was similar during both day- and night-time, a predominant low frequency peak was observed during the day.(ABSTRACT TRUNCATED AT 250 WORDS)