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

恢复型左心辅助装置(RDLVAD)是一种新型的左心辅助装置，其特点是收缩期室后负荷显著降低，舒张期室壁不受舒张性或舒张性限制，从而促进心脏恢复。它由一个带瓣的心尖管道、一个顺应性后负荷控制室(ACC)和一个连续流动式血泵组成。在模拟循环和离体兔心脏灌流实验中，我们研究了适合于RDLVAD实现上述特征的主要成分的大小和性质。1.在模拟循环中表现的严重左心衰竭状态下，研究了3种不同心尖瓣和4种不同AC之间的12种组合对左室压(LVP)、ACC压和最大心输出量的影响。内径分别为9 mm和13 mm的心尖瓣太小，不能减轻心脏负荷。开放面积是23 mm主动脉瓣的60%的18 mm心尖瓣和心搏出量的一半的ACC是最小的，以不断实现显著降低的心室后负荷和充足的血液供应；开发的压力低至平均收缩压27 mmHg，峰值LVP为47 mm Hg，即使ACC的顺应性低至0.1-0.6mL/mm Hg2，最大心输出量(=最大泵流量)也能够产生5.8L/min的心输出量。我们已经警告过，连续流动型LVAD会随着泵流量的增加而增加阻碍心室松弛和充盈的风险。这一现象在模拟循环和动物实验中都有表现。在一些孤立的心脏中，当泵的流量增加时，心率也会突然增加。另一方面，RDLVAD不限制心室松弛或充盈。

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.