Abstract 2984: Non-pulsatile Left Ventricular Assist Device (LVAD) Patients Show Impaired Cerebral Autoregulation in Response to Upright Tilt
Introduction: The importance of pulsatile blood flow in cerebral autoregulation is unknown. We hypothesized that pulsatility is crucial in this process. To test this hypothesis we studied cerebral blood flow in patients with pulsatile and non-pulsatile LVADs.
Methods: 9 LVAD patients were studied: 4 with pulsatile devices and 5 with non-pulsatile devices (age range 20–74 yrs). Hemodynamics (BP, HR), cerebral blood flow velocity (CBFV) from transcranial Doppler, and end tidal CO2 (EtCO2) were recorded in the supine position and with graded head-up tilting (HUT).
Results: Mean blood pressure (MBP - reconstructed brachial BP measured at the finger) changed minimally during upright tilt (p=0.5) with comparable responses between groups (p=0.95) (Figure⇓ top). Pulse pressure (PP) was almost unmeasurable in the non-pulsatile patients and less than the pulsatile LVAD group (p=0.04). The decrease in CBFV from the supine position to 60° HUT was greater in the non-pulsatile group (27%; p=0.04) than in the pulsatile group (8%; p=0.8) (Figure⇓ bottom). This difference was not due to a change in EtCO2 (Δ 0.8 mmHg with HUT in the pulsatile group vs. Δ .8mmHg with HUT in the non-pulsatile group; p=0.15), which was similar between the groups.
Conclusions: Non-pulsatile LVAD patients have impaired cerebral autoregulation during HUT. Impaired flow-mediated dilation in the brain may be influenced by lack of pulsatility and could contribute to neurological events in these patients. This observation substantiates the hypothesis that pulsatility is crucial for cerebral autoregulation, though more data are required to determine the clinical significance of this finding.