Central and Cerebral Circulation in Early Stages After LVAD Implantation

Overview

This trial will evaluate patients with a mechanical Left Ventricular Assist Device (LVAD) in early stages after surgical implantation. Within the first 2 days of postoperative ICU care, 20 patients will firstly be exposed to 4 different LVAD pump flow settings with a stable blood pressure. A second intervention will be mean arterial blood pressure (MAP) adjustments to 4 preset levels (60-70-80 and 90 mmHg) with a constant preset LVAD flow. The two manipulations; 1) Constant MAP with variation of LVAD flow and 2) Constant LVAD flow with variation of MAP, will be monitored by Central hemodynamic parameters, echocardiographic parameters and cerebral blood flow velocity (CBFV) parameters. The purpose of the trial is to find the optimal combination of LVAD pump flow, mean arterial pressure and right heart ventricle function for each patient. And at the same time describe the effect of flow and pressure variations on CBFV.

Patients with severe left ventricular heart failure and estimated short expected survival time despite optimal medical therapy can be treated with a left ventricular mechanical heart pump - described as a Left Ventricular Assist Device (LVAD). The LVAD can be used as a bridge for patient survival prior to heart transplantation, or as a destination therapy for terminal heart failure. The LVAD delivers a non-pulsatile blood flow into the patients aorta, supporting and/or taking over the left ventricular function. However the right heart ventricle (RV) is not supported by the LVAD. RV failure is a major threat to the patient, in particular during the early postoperative period. Postoperative RV failure after LVAD implantation is medically treated, but in severe cases a mechanical temporary right ventricular assist (RVAD) may be needed. Patients in need of postoperative RVAD after an LVAD implant have a significantly increased mortality. Thus it is of vital importance to balance the LVAD pump flow against the native RV function in order to avoid the need for an RVAD. If the LVAD flow rate is set too low the RV will be exposed to a high afterload and risk failure. If, on the other hand, the LVAD flow is set too high it can potentially completely empty the left ventricle with secondary geometrical distortion of the heart chambers and an increased venous return to the RV. This too increases the risk for RV failure. To find the optimal LVAD flow rate it is custom to do an extensive evaluation of central hemodynamic parameters (Cardiac Output(CO), Pulmonary Capillary Wedge Pressure (PCWP), Pulmonary Arterial Pressure (PAP), Central Venous Pressure (CVP)) and cardiac echocardiographic evaluation of RV function at different LVAD pump flow rates and MAP. The instant balance between RV filling pressure-CVP, and LV filling pressure-PCWP, is on the other hand easy to obtain. However it is not known if these measurements can be used to obtain an optimal LVAD flow rate. Furthermore all mechanically driven circulatory support devices, including LVAD, will expose the peripheral arterial circulation to a non-pulsatile blood flow.There are few previous reports on how an LVAD affects the cerebral blood flow autoregulation and microembolic load at different settings and MAP. This investigation aims to describe these cerebral effect af an LVAD using a continous Transcranial Doppler (TCD) detection of cerebral arteries.