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Assessment of cardiac baroreflex function during fixed atrioventricular pacing using baroreceptor-stroke volume
Tomiya Yasumasu1, Haruhiko Abe, Yasushi Oginosawa
1First Department of Medical Technology, School of Health Sciences, University of Occupational and Environmental health, Kitakyushu, Japan.
Unlabelled:
Baroreflex sensitivity in paced patients.
Introduction:
The baroreceptor-heart rate (HR) reflex has prognostic value in cardiovascular medicine. However, it cannot be used in chronotropically incompetent or paced patients. In healthy subjects, the baroreceptor-stroke volume (SV) reflex, with power spectral analysis of SV and blood pressure (BP) variations in the low-frequency band, serves as an alternate measure of the baroreceptor-cardiac reflex. This study examined the baroreceptor-stroke volume (SV) reflex sensitivity in the supine and 60 degrees upright positions in paced patients.
Methods And Results:
We studied 16 recipients of dual-chamber pacemakers paced at a fixed rate. The hemodynamics and baroreceptor-SV reflex sensitivity were measured during atrioventricular (AV) sequential pacing every 5 minute in the supine and 60 degrees upright positions. Mean SV decreased from 42.0+/-20.1 mL in the supine to 36.6+/-16.1 mL in the upright position (P<0.05), whereas BP and total peripheral resistance did not change. A significant fall in baroreceptor-SV reflex sensitivity from 29.2+/-18.0%/mmHg to 19.5+/-15.5%/mmHg was observed during upright tilt (P<0.005).
Conclusion:
Fixed-rate AV sequential pacing did not blunt the decrease in baroreceptor-SV reflex sensitivity consistent with the arterial baroreflex gain response to upright posture. The decreased baroreceptor-SV reflex sensitivity occurring with the upright posture may reflect a baroreflex-induced inotropic effect secondary to vagal withdrawal and sympathetic activation.
