Evaluation of the baroreceptor-heart rate reflex by 24-hour intra-arterial blood pressure monitoring in humans.

TLDR

The baroreceptor‑heart rate reflex shows marked within‑subject sensitivity variations driven by hemodynamic, temporal, and behavioral factors. The study used 24‑hour intra‑arterial blood‑pressure monitoring in 20 subjects to identify linear sequences of three or more consecutive beats with simultaneous changes in systolic pressure and pulse interval, revealing baroreceptor‑heart rate reflex dynamics. Normotensive subjects displayed numerous short linear sequences with steep slopes that increased at night, whereas hypertensive subjects had fewer, flatter sequences and lacked the nighttime slope rise, highlighting impaired baroreceptor‑heart rate reflex in hypertension. Abstract truncated at 250 words.

Abstract

The baroreceptor control of the sinus node was evaluated in 10 normotensive and 10 age-matched essential hypertensive subjects in whom ambulatory blood pressure was recorded intra-arterially for 24 hours and scanned by a computer to identify the sequences of three or more consecutive beats in which systolic blood pressure (SBP) and pulse interval (PI) progressively rose (+PI/+SBP) or fell (-PI/-SBP) in a linear fashion, according to a method validated in cats. In normotensive subjects, several hundred +PI/+SBP and -PI/-SBP sequences of 3 beats were found whereas the number of sequences of 4, 5, and more than 5 beats showed a progressive drastic reduction. The mean slopes of +PI/+SBP (7.6 +/- 2.0 msec/mm Hg) and -PI/-SBP (6.4 +/- 1.5 msec/mm Hg) sequences were similar, but in both instances there was a large scattering of the values around the mean (variation coefficients: 64.2 +/- 4.7 and 62.6 +/- 2.4%). The slopes decreased as a function of the sequence length and baseline heart rate and increased to a marked extent during the night as compared with daytime values. All sequences were more rare (-33.2% for +PI/+SBP and -31.7% for -PI/-SBP) and less steep in hypertensive subjects (-40.3 and -36.2%, respectively), who failed to show the marked nighttime increase in slope observed in normotensive subjects. To our knowledge, these observations provide the first description in humans of the baroreceptor-heart rate reflex in daily life. This reflex is characterized by marked within-subject variations in sensitivity due in part to hemodynamic, temporal, and behavioral factors. (ABSTRACT TRUNCATED AT 250 WORDS)