Motomi Shiono

Clinical evaluation of left ventricular assist device in six cases

During recent years, ventricular assist devices (VADs) have demonstrated early clinical applications in circulatory support, with the potential of increasing use. VAD systems have been used in more than 50 cases in Japan, although a significant change in survival was achieved in only 15% of the cases. There have been a number of difficulties inherent to both the hardware and techniques of clinical application. Retrospective analysis of six cases where VADs were applied clinically are reviewed. Left ventricular assist devices (LVADs) were indicated in five patients for cardiopulmonary bypass (CPB) weaning and in one patient for postcardiotomy low output syndrome (LOS). Five cases could be weaned from LVAD, however one patient failed and was classified as LVAD dependent. In the group which could be weaned from LVAD, two patients died from multiple organ failure (MOF) and two from heart failure. Longterm survival was significant in only one patient. A clinical evaluation of the LVADs suggests that there was a remarkable hemodynamic improvement in postoperative pump failure in all six cases, and total cardiac output index should be maintained at more than 2.2–2.5 1/min/m2 for the prevention of hypoperfusion of vital organs. Antithrombogenicity of the system was satisfactory, though thrombi were observed microscopically. The method and indication for removal of LVAD have not been established; however, these problems may be resolved as the number of clinical cases increase in future.

Development of a Seal-Less Motor-Driven Centrifugal Blood Pump (Baylor Gyro Pump)

To overcome the seal shaft-related problems of conventional centrifugal blood pumps, a new seal-less centrifugal blood pump capable of more than 2 weeks’ operation was designed by supporting the rotating part of the pump with two pivot bearings. The rotor of a brushless direct current (DC) motor is placed in the inlet side of the pump and is directly connected with the impeller. The blood passes through the gap around the rotor and enters the impeller eye; the rotor impeller rotates as a “gyroscope” in the pump. The pump generated 31/min against 86 mmHg at 2000 rpm. Indices of hemolysis of 0.005 was obtained in hemolysis tests using bovine blood.

Clinical Applications and Problems of Pneumatic Pulsatile Ventricular Assist Devices

Since October 1982, we have employed a pneumatic ventricular assist device (VAD; Nippon Zeon, Tokyo, Japan) for profound heart failure in 16 post-cardiotomy settings. The etiology of the underlying diseases was ischemic in four patients, valvular in six, combined ischemic and valvular in four, and congenital in one, and “cardiomyopathy” in one patient. Average assist duration was 86 h, with left side assist being employed in 13 patients and right side assist in 3 patients. Weaning rate from the device was 66% and survival rate was approximately 20%. Causes of death were: multiple organ failure in 40%, ventricular failure in 25% and other causes in the remaining patients. Infection and thromboembolic complications were not observed during assistance. Optimization of assist flow was achieved by monitoring hemodynamic and echo-cardiographic data. Hemodynamic criteria for weaning from the device were also established; cardiac index (CI) > 2.51/min/m2, pulmonary capillary wedge pressure (PCWP) < 15 mmHg, etc. Monitoring of the coagulation system has also been important for avoiding multi-organ failure and achieving long-term survival. Comparisons of pulsatile and nonpulsatile devices have been considered. The results suggest that this system, which is currently available commercially, is versatile for use in profound heart failure in the postcardiotomy setting and could also be employed as a short-term or intermediate-term device in an emergency setting and in bridge-to-transplant patients.