Investigation of Usefulness of "Recovery-Directed Left Ventricular Assist Device" invented based on a new concept

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Recovery-Directed Left Ventricular Assist Device (RDLVAD) is a new type LVAD characterized by remarkable reduction in ventricular afterload during systole and no restriction of ventricular relaxation or dilatation during diastole, thereby promoting cardiac recovery. It consists of a valved apical conduit, a compliant afterload-controlling chamber (ACC), and a continuous-flow type blood pump. In both experiments using a mock circulation and isolated perfused rabbit hearts, we investigated sizes and properties of the main components that are appropriate for RDLVAD to achieve the above features.1.In the state of severe left heart failure represented in the mock circulation, the effect of each of 12 combinations made between 3 different apical valves and 4 different ACCs on the left ventricular pressure (LVP), the ACC pressure and the maximum cardiac output was studied. The apical valves, 9 and 13 mm in internal diameter, were too small to reduce the ventricular load. The 18-mm apical valve, whose opening area was 60% of that of the 23-mm aortic valve, and the ACC half as large as the stroke volume were smallest for constantly achieving significant reduction in ventricular afterload and sufficient blood supply ; the developed pressure as low as a mean systolic LVP of 27mmHg and a peak LVP of 47mmHg was capable of producing a maximum cardiac output (=maximum pump flow) of 5.8L/min even if the compliance of ACC was as low as 0.1-0.6mL/mmHg.2.We have warned that continuous-flow type LVADs increase the risk of impeding ventricular relaxation and filling as a pump flow rate rises. This phenomenon was shown both in the mock circulation and animal experiments. In some isolated hearts, heart rate also suddenly increased when the pump flow was raised. On the other hand, the RDLVAD did not restrict ventricular relaxation or filling.