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Published on: May 11, 2015
Restoration of Pulsatile Flow Reduces Sympathetic Nerve Activity Among Individuals With Continuous-Flow Left
William K Cornwell1, Takashi Tarumi1, Abigail Stickford1
1From 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.).
Restoring pulsatile flow in continuous-flow left ventricular assist devices by adjusting pump speed reduces muscle sympathetic nerve activity (MSNA). This occurs via the arterial baroreceptor reflex, suggesting a potential for improved patient outcomes.
Area of Science:
- Cardiovascular physiology
- Medical device engineering
- Neuroscience
Background:
- Current left ventricular assist devices (LVADs) provide nonpulsatile flow, increasing muscle sympathetic nerve activity (MSNA).
- This increase in MSNA is thought to be mediated by the arterial baroreceptor reflex.
- Investigating pulsatile flow restoration in LVADs may offer a method to mitigate this sympathetic response.
Purpose of the Study:
- To determine if modulating LVAD pump speed to restore pulsatile flow can reduce MSNA.
- To assess the role of the arterial baroreceptor reflex in mediating these changes.
- To evaluate the hemodynamic and neural responses to altered pulsatile flow in LVAD patients.
Main Methods:
- Ten men and three women with Heartmate II continuous-flow LVADs were studied.
- Beat-to-beat blood pressure, carotid ultrasonography, and MSNA were continuously recorded.
- LVAD pump speed was altered to induce step changes in pulsatile flow, and responses were measured.
Main Results:
- Reducing LVAD pump speed increased pulse pressure and carotid artery distension.
- Muscle sympathetic nerve activity (MSNA) significantly decreased with reduced pump speed.
- The reduction in MSNA was inversely related to the increase in pulse pressure.
Conclusions:
- Modulating LVAD pump speed to restore pulsatile flow decreases MSNA via arterial baroreceptor activation.
- Increased pulsatility leads to greater baroreceptor distortion and subsequent sympathetic decline.
- Further research is needed to ascertain if reducing MSNA with pulsatile flow improves clinical outcomes.
