Baroreflex Gain Predicts Blood Pressure Recovery During Simulated Ventricular Tachycardia in Humans

Abstract

Background-Despite similar degrees of left ventricular dysfunction and similar tachycardia or pacing rate, blood pressure (BP) response and symptoms vary greatly among patients. Sympathetic nerve activity (SNA) increases during sustained ventricular tachycardia (VT), and the magnitude of this sympathoexcitatory response appears to contribute to the net hemodynamic outcome. We hypothesize that the magnitude of sympathoexcitation and thus arterial baroreflex gain is an important determinant of the hemodynamic outcome of VT. Methods and Results-We evaluated the relation between arterial baroreflex sympathetic gain and BP recovery during rapid ventricular pacing (VP) in patients referred for electrophysiological study. Efferent postganglionic muscle SNA, BP, and central venous pressure (CVP) were measured in 14 patients during nitroprusside infusion and during VP at 150 (nϭ12) or 120 (nϭ2) bpm. Arterial baroreflex gain was defined as the slope of the relationship of change in SNA to change in diastolic BP during nitroprusside infusion. Recovery of mean arterial pressure (MAP) during VP was measured as the increase in MAP from the nadir at the onset of pacing to the steady-state value during sustained VP. Arterial baroreflex gain correlated positively with recovery of MAP (rϭ0.57, Pϭ0.034). No significant correlation between ejection fraction and baroreflex gain (rϭ0.48, Pϭ0.08) or BP recovery (rϭ0.41, Pϭ0.15) was found. When patients were separated into high versus low baroreflex gain, the recovery of MAP during simulated VT was significantly greater in patients with high gain. Conclusions-These data strongly suggest that arterial baroreflex gain contributes significantly to hemodynamic stability during simulated VT. Knowledge of baroreflex gain in individual patients may help the clinician tailor therapy directed toward sustained VT. (Circulation. 1999;100:381-386.)

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Serotonin Reuptake Inhibitor (Paxil) Does Not Prevent the Vasovagal Reaction Associated With Carotid Sinus Massage and/or Lower Body Negative Pressure in Healthy Volunteers

“…Efferent post-ganglionic muscle SNA was recorded from the right peroneal nerve as previously described. 8,9 Briefly, a sterile microelectrode was inserted into a fascicle of the peroneal nerve near the fibular head. The nerve signals were amplified, filtered (700 to 2000 Hz), rectified, and discriminated.…”

Effect of short-term rapid ventricular pacing followed by pacing interruption on arterial blood pressure in healthy pigs and pigs with tachycardiomyopathy

“…1997). The studies published so far have shown that the greater sensitivity of baroreceptor reflexes is associated with better tolerance of ventricular tachycardia (Hamdan et al 1999). Poor ventricular tachycardia tolerance may be related to inadequate stimulation of the sympathetic nervous system.…”