Biventricular Pacing Decreases Sympathetic Activity Compared With Right Ventricular Pacing in Patients With Depressed Ejection Fraction

Abstract

Background-Although there have been few studies in which the hemodynamic effects of right ventricular (RV) and left ventricular (LV) pacing were compared with those of biventricular (BV) pacing, the autonomic changes during these different pacing modes remain unknown. We hypothesized that BV pacing results in improved hemodynamics and a decrease in sympathetic nerve activity (SNA) compared with single-site pacing. Methods and Results-Thirteen men with a mean ejection fraction of 0.28Ϯ0.7 were enrolled in the study. Arterial blood pressure (BP), central venous pressure (CVP), and SNA were recorded during 3 minutes of right atrial (RA)-RV, RA-LV, and RA-BV pacing at a rate 10 beats faster than sinus rhythm. BP was greater during LV (151Ϯ7/ 85Ϯ3 mm Hg) and BV (151Ϯ6/85Ϯ3 mm Hg) pacing than during RV pacing (146Ϯ7/82Ϯ3 mm Hg) (PϽ0.05). There were no differences in CVP among all pacing modes (Pϭ0.27). SNA was significantly less (PϽ0.02) during both LV (606Ϯ35 U) and BV (582Ϯ41 U) pacing compared with RV pacing (685Ϯ32 U) (PϽ0.02). Although not statistically significant (Pϭ0.08 to 0.14), there was a trend for patients with a narrow QRS to have a lower mean BP and higher SNA during LV pacing than during BV pacing (rϭ0.42 to 0.49). Conclusions-LV-based pacing results in improved hemodynamics and a decrease in SNA compared with RV pacing in patients with LV dysfunction regardless of the QRS duration.

Hemodynamic changes during cardiac resynchronization therapy

“…This was reflected by a lower heart rate at rest and at 25 watts and lower levels of serum brain natriuretic peptide. This fits well with the findings of Hamdan et al 6 of an acute reduction in sympathic nerve activity by biventricular pacing. The second benefit seems to be a higher mean arterial pressure both at rest and, even more pronounced, at exertion, accompanied by reduced filling pressures.…”

Acute effects of cardiac resynchronization therapy on arterial distensibility and serum norepinephrine levels in advanced heart failure

“…Cha et al [25] found that clinical and cardiac functional improvements were paralleled by significant improvements in NE reuptake function as measured by metaiodobenzylguanidine ( 123 I-MIBG), an NE analog, uptake and retention after CRT for advanced cardiomyopathy. Also, CRT inhibits arterial baroreflex mediated sympathoexcitation occurring in CHF, and, therefore, reduces adrenergic nerve outflow measured by microneurography [26,27].…”

Cellular and Molecular Aspects of Dyssynchrony and Resynchronization

“…Myocytes from dyssynchronous HF, however, displayed very little response to isoproterenol stimulation, whereas CRT restores this to almost normal/healthy levels ( Figure 2D) [35]. This mirrors changes observed in CRT patients, who display enhanced responses to cardiac sympathetic stimulation [40,41], although CRT acutely blunts sympathetic tone [42].The mechanism for restored β-adrenergic signaling highlights the fact that CRT is not just re-establishing electromechanical synchrony, but engages sub-cellular mechanisms that improve reserve function. HF is characterized by a decline in β-adrenergic stimulation signaling, and this is observed in both synchronous or dyssynchronous forms.…”