Longitudinal Assessment of Hemodynamic and Autonomic Responses to Mechanical Circulatory Support Among Advanced Heart Failure Patients

Abstract

Purpose Determine the hemodynamic and autonomic response to implantation of durable continuous-flow (CF) left ventricular assist device (LVAD) among individuals with advanced heart failure (AHF). Background HF leads to neurohormonal activation with exaggerated increases in sympathetic tone. This hyperadrenergic environment is positively correlated with HF severity and mortality. Previous investigations have demonstrated that non-physiologic reductions in pulsatility associated with CF-LVADs, contributes to elevated levels of sympathetic nerve activity. Therefore, it is thought that CF-LVAD implantation leads to heightened sympathetic tone. However, there are no data examining longitudinal changes in hemodynamics and/or sympathetic tone prior to and following device implantation. Methods Nine individuals (59 ± 9 yrs, 8 males) scheduled for CF-LVAD implantation underwent hemodynamic assessment ∼two weeks prior to, and ∼three months following surgery. At those dates participants completed a graded head-up tilt (HUT) at supine, 30 and 60 degrees, with assessment of heart rate (HR), blood pressure (BP) by arterial catheter, and plasma catecholamines at each position. Results Hemodynamic and catecholamine responses to HUT are displayed in Figure 1. HR and MAP were similar prior to and following CF-LVAD implantation (Supine MAP 78.9 ± 7.5 v. 87.8 ± 14 mmHg, for pre- and post-LVAD respectively, P=0.76). However, pulse pressure was significantly reduced following device implantation (47.3 ± 18, 23.7 ± 12 mmHg for supine pre- and post-LVAD, respectively, P=0.009). Despite the reduction in pulsatility, plasma norepinephrine levels were significantly reduced following device implantation (pre-LVAD 712 ± 374, post- LVAD 319 ± 156 pg/ml, both supine, P =0.016). Notably, pre-LVAD supine norepinephrine levels were significantly greater than post-LVAD levels at a 60-degree HUT (712 ± 374 v. 481 ± 234 pg/ml, P=0.25), indicating a marked reduction in autonomic tone following device implantation. Discussion Despite a reduction in physiologic pulsatility following CF-LVAD implantation, autonomic tone, as measured by plasma norepinephrine levels, significantly declines following device implantation. However, norepinephrine levels observed following device implantation are elevated compared to levels observed among healthy individuals. Together, this information suggests that CF-LVAD implantation improves, but does not reverse, the hyperadrenergic environment that is characteristic of AHF.