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Heart rate control of blood pressure variability in children: a study in subjects with fixed ventricular pacemaker
I Constant1, E Villain, D Laude
1Service d'Anesthésie Réanimation Pédiatrique, Hôpital d'enfants Armand Trousseau, 26 Av. du Dr Arnold Netter, 75571 Paris, France.
Insights
Heart rate variability influences blood pressure variability in children. Suppressing heart rate fluctuations significantly reduces diastolic blood pressure variability, challenging existing theories on blood pressure control.
Area of Science:
- Pediatric Cardiology
- Autonomic Nervous System Function
- Cardiovascular Physiology
Background:
- Heart rate variability (HRV) plays a role in cardiovascular regulation.
- Understanding HRV's impact on blood pressure variability (BPV) is crucial for pediatric health.
Purpose of the Study:
- To investigate the influence of heart rate variability on blood pressure variability in children.
- To compare HRV and BPV in healthy children versus those with fixed ventricular pacemaker rhythm.
Main Methods:
- Continuous measurement of arterial blood pressure and heart rate (ECG).
- Calculation of power spectra for heart rate and blood pressure (systolic and diastolic).
- Assessment during supine, orthostatic positions, and active standing.
Main Results:
- Healthy children showed significant HRV; pacemaker group had none.
- Systolic blood pressure variability was minimally affected by HRV suppression.
- Diastolic blood pressure fluctuations decreased notably with suppressed HRV, especially in the pacemaker group.
- Pacemaker group experienced a greater early drop in systolic blood pressure upon standing.
Conclusions:
- Heart rate fluctuations enhance blood pressure variability in healthy children.
- Suppressed HRV significantly impacts diastolic blood pressure variability, potentially altering baroreflex control mechanisms.
- Findings may challenge established theories of diastolic blood pressure regulation in adults.
Abstract:
1. To investigate the influence of heart rate variability on blood pressure variability, short-term variability in heart rate and blood pressure was studied in 10 children with fixed ventricular pacemaker rhythm (80 beats/min). Ten healthy children, in sinus rhythm, served as a reference population. 2. Arterial blood pressure and heart rate were measured continuously using a finger arterial device and an ECG respectively. Power spectra for heart rate and blood pressure (systolic and diastolic) were calculated in both supine and orthostatic positions. In addition, acute changes in blood pressure and heart rate during active standing were studied. 3. Healthy children exhibited considerable heart rate variability, which was slightly more pronounced in the supine position, while children with a fixed ventricular rate had no heart rate variability in either position. 4. Despite the differences in heart rate variability, mean systolic blood pressure and its variability profiles were poorly affected by the suppression of heart rate variability. The lack of autonomic control on the sinus node was associated with a reduction in magnitude of the changes in systolic blood pressure variability induced by orthostatic posture. 5. The suppression of heart rate fluctuations induced a noticeable decrease in diastolic blood pressure fluctuations, which was most conspicuous in the children with fixed cardiac rhythm when in the supine position. This may be explained by the lack of diastolic blood pressure fluctuations, physiologically due to heart rate fluctuations through the run-off effect: the longer the cardiac cycle, the greater the diastolic pressure decay. These results may challenge the classical theory of baroreflex-mediated diastolic blood pressure control described in adult patients. 6. During active standing, the early drop in systolic blood pressure was greater in subjects with fixed ventricular rhythm. A rise in heart rate of 36 beats/min was observed in the healthy subjects in response to active standing. 7. We conclude that in normal children, heart rate fluctuations increase the blood pressure variability rather than buffering it. However, during acute orthostatic stress, the abrupt baroreflex-mediated heart rate rise may partly compensate for the reduction in blood pressure.