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

恢复导向左室辅助装置（recovery - directed Left Ventricular Assist Device， RDLVAD）是一种新型左室辅助装置，其特点是在收缩期显著降低心室后负荷，在舒张期不限制心室舒张或扩张，从而促进心脏恢复。它由一个带瓣的根尖导管、一个柔性后负荷控制室（ACC）和一个连续血流型血泵组成。在模拟循环和离体灌注兔心脏的实验中，我们研究了适合RDLVAD的主要成分的大小和性质，以实现上述特征。以模拟循环为代表的严重左心衰竭状态下，研究3个不同顶瓣与4个不同ACC的12种组合对左室压（LVP）、ACC压及最大心输出量的影响。内径9 mm和13 mm的尖瓣太小，无法减轻心室负荷。18mm的顶瓣，其开放面积为23mm主动脉瓣的60%，ACC为脑卒中容积的一半，是持续显著降低心室后负荷和充足血供的最小瓣膜；即使ACC的顺应性低至0.1-0.6mL/ mmhg，当平均收缩期LVP低至27mmHg，峰值LVP为47mmHg时，仍能产生5.8L/min的最大心输出量（=最大泵流量）。我们已经警告过，随着泵流量的增加，连续血流型lvad会增加阻碍心室舒张和充盈的风险。这一现象在模拟循环和动物实验中都得到了证实。在一些孤立的心脏中，当泵流量增加时，心率也会突然增加。另一方面，RDLVAD不限制心室舒张或充盈。

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.