Evaluation of the baroreceptor-heart rate reflex by 24-hour intra-arterial blood pressure monitoring in humans.
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)
Parati
G
G
Cattedra di Semeiotica Medica, Università di Milano, Italy.
Di Rienzo
M
M
Bertinieri
G
G
Pomidossi
G
G
Casadei
R
R
Groppelli
A
A
Pedotti
A
A
Zanchetti
A
A
Mancia
G
G
D000328:Adult; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000379:methods*; D002940:Circadian Rhythm; D005260:Female; D006339:Heart Rate; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D011311:Pressoreceptors / Q000502:physiology*; D011674:Pulse; D012018:Reflex / Q000502:physiology*; D012849:Sinoatrial Node / Q000502:physiology*