From Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas (W.K.C., T.T., A.S., J.L., M.R., R.P., Q.F., B.D.L.); Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas (W.K.C., C.F., J.K., C.A., M.H.D., B.D.L.); and Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA (D.M.).
Circulation. 2015 Dec 15;132(24):2316-22. doi: 10.1161/CIRCULATIONAHA.115.017647. Epub 2015 Oct 28.
Current-generation left ventricular assist devices provide circulatory support that is minimally or entirely nonpulsatile and are associated with marked increases in muscle sympathetic nerve activity (MSNA), likely through a baroreceptor-mediated pathway. We sought to determine whether the restoration of pulsatile flow through modulations in pump speed would reduce MSNA through the arterial baroreceptor reflex.
Ten men and 3 women (54 ± 14 years) with Heartmate II continuous-flow left ventricular assist devices underwent hemodynamic and sympathetic neural assessment. Beat-to-beat blood pressure, carotid ultrasonography at the level of the arterial baroreceptors, and MSNA via microneurography were continuously recorded to determine steady-state responses to step changes (200-400 revolutions per minute) in continuous-flow left ventricular assist device pump speed from a maximum of 10,480 ± 315 revolutions per minute to a minimum of 8500 ± 380 revolutions per minute. Reductions in pump speed led to increases in pulse pressure (high versus low speed: 17 ± 7 versus 26 ± 12 mm Hg; P<0.01), distension of the carotid artery, and carotid arterial wall tension (P<0.05 for all measures). In addition, MSNA was reduced (high versus low speed: 41 ± 15 versus 33 ± 16 bursts per minute; P<0.01) despite a reduction in mean arterial pressure and was inversely related to pulse pressure (P=0.037).
Among subjects with continuous-flow left ventricular assist devices, the restoration of pulsatile flow through modulations in pump speed leads to increased distortion of the arterial baroreceptors with a subsequent decline in MSNA. Additional study is needed to determine whether reduction of MSNA in this setting leads to improved outcomes.
目前一代的左心室辅助装置提供的循环支持是最小或完全非搏动性的，并与肌肉交感神经活动（MSNA）的显著增加相关，这可能是通过压力感受器介导的途径。我们试图确定通过调节泵速来恢复脉动血流是否会通过动脉压力感受器反射来降低 MSNA。
10 名男性和 3 名女性（54±14 岁）接受了 Heartmate II 连续流左心室辅助装置的血流动力学和交感神经评估。通过微神经记录连续记录血压的搏动、颈动脉在动脉压力感受器水平的超声检查以及 MSNA，以确定在连续流左心室辅助装置泵速从最高 10480±315 转/分降至最低 8500±380 转/分的阶跃变化时的稳态反应。降低泵速会导致脉搏压增加（高速与低速：17±7 与 26±12mmHg；P<0.01），颈动脉扩张和颈动脉壁张力增加（所有指标均为 P<0.05）。此外，尽管平均动脉压降低，但 MSNA 也降低（高速与低速：41±15 与 33±16 次/分钟；P<0.01），并与脉搏压呈负相关（P=0.037）。
在连续流左心室辅助装置的受试者中，通过调节泵速恢复脉动血流会导致动脉压力感受器的变形增加，随后 MSNA 下降。需要进一步研究以确定在这种情况下降低 MSNA 是否会导致更好的结果。
