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We developed a novel controller for a continuous-flow left ventricular assist device (EVAHEART) that can change the pump's rotational speed (RS) in synchronization with a patient's myocardial electrocardiogram (ECG) with the aim of facilitating cardiac recovery. We previously presented various applications of this system in animal models, but there remained a concern that the repeated acceleration and deceleration of the impeller may induce additional hemolysis. In this study, we evaluated the blood trauma and motor power consumption induced by our system in a mock circulation. We evaluated our system with a 60-bpm pulse frequency and a variance between the high and low RSs of 500 rpm (EVA-P; n = 4). The continuous modes of EVAHEART (EVA-C; n = 4) and ROTAFLOW (n = 4) were used as controls. The pumps were examined at a mean flow rate of 5.0 ± 0.2 L/min against a mean pressure head of 100 ± 3 mmHg for a 4-h period. As a result, the normalized indexes of the hemolysis levels of EVA-P and EVA-C were 0.0023 ± 0.0019 and 0.0023 ± 0.0025, respectively, and their difference was not significant. The estimated mean motor power consumptions of EVA-C and EVA-P were 6.24 ± 0.33 and 7.19 ± 0.93 W, respectively. When a novel ECG-synchronized RS-change system was applied to EVAHEART, the periodic RS change with a 500-rpm RS variance did not affect the hemolysis at a 60-bpm pulse frequency.

Aortic insufficiency (AI) is a serious complication for patients on long-term support with left ventricular assist devices (LVAD). Postoperative aortic valve opening is an important predictor of AI. A system is presently available that can promote native aortic flow by reducing rotational speed (RS) for defined intervals. However, this system can cause a reduction in pump flow and lead to insufficient support. We therefore developed a novel "delayed copulse mode" to prevent AI by providing both minimal support for early systole and maximal support shortly after aortic valve opening by changing the RS in synchronization with heartbeat. To evaluate whether our drive mode could open the aortic valve while maintaining a high total flow (sum of pump flow and native aortic flow), we installed a centrifugal LVAD (EVAHEART(®); Sun Medical) in seven goats each with normal hearts and acute LV dysfunction created by micro-embolization of the coronary artery. We intermittently switched the drive mode from continuous (constant RS) with 100 % bypass to delayed copulse mode with 90 % bypass. Total flow did not significantly change between the two modes. The aortic valve opened when the delayed copulse mode was activated. The delayed copulse mode allowed the aortic valve to open while maintaining a high total flow. This novel drive mode may considerably benefit patients with severe heart failure on long-term LVAD support by preventing AI.

Using simple, safe, and economical in-body tissue engineering, autologous valved conduits (biovalves) with the sinus of Valsalva and without any artificial support materials were developed in animal recipients’ bodies. In this study, the feasibility of the biovalve as an aortic valve was evaluated in a goat model. Biovalves were prepared by 2-month embedding of the molds, assembled using two types of specially designed plastic rods, in the dorsal subcutaneous spaces of goats. One rod had three projections, resembling the protrusions of the sinus of Valsalva. Completely autologous connective tissue biovalves (type VI) with three leaflets in the inner side of the conduit with the sinus of Valsalva were obtained after removing the molds from both terminals of the harvested implants with complete encapsulation. The biovalve leaflets had appropriate strength and elastic characteristics similar to those of native aortic valves; thus, a robust conduit was formed. Tight valvular coaptation and a sufficient open orifice area were observed in vitro. Biovalves (n = 3) were implanted in the specially designed apico-aortic bypass for 2 months as a pilot study. Postoperative echocardiography showed smooth movement of the leaflets with little regurgitation under systemic circulation (2.6 ± 1.1 l/min). α-SMA–positive cells appeared significantly with rich angiogenesis in the conduit and expanded toward the leaflet tip. At the sinus portions, marked elastic fibers were formed. The luminal surface was covered with thin pseudointima without thrombus formation. Completely autologous biovalves with robust and elastic characteristics satisfied the higher requirements of the systemic circulation in goats for 2 months with the potential for valvular tissue regeneration.