[Development and evaluation of ventricular assist blood pump to salvage patients with profound heart failure].

One of the most important characteristics of a ventricular assist device (VAD) is good antithrombogenicity such that the circulating blood does not clot on the surface even when the bypass flow through the device is reduced at the time of weaning-off. A pneumatic and diaphragm-type VAD with excellent antithrombogenicity was developed for clinical use. The pump is made of Japanese-made segmented polyether polyurethane and the maximum output is 7.0 L/min. If the bypass flow was maintained above 2.0 L/min during early postoperative period, thrombus formation was rarely observed even when the flow rate decreased afterwards in chronic animal experiments using 30 goats. Experimental analyses suggested that a biolization mechanism of the material surface covered by absorbed plasma protein might play a major role in the establishment of antithrombogenicity of the pump. No mechanical failure, thrombosis, calcification, and complication in experimental animals occurred when the VAD manufactured under our good quality control system was driven adequately. These results proved that the VAD could be used reliably for at least 3 months. In conclusion, the VAD is safely applicable to clinical cases and contributes to treatments of profound heart failure patients.

[Human heart recovery during weaning from a left ventricular assist system: time course and outcome prediction].

To investigate the time course of recovery of a failing heart using the left ventricular assist system (LVAS) and to predict the outcome of weaning from the LVAS, 14 patients with a failing heart were studied. Among them, 5 had recovered and survived for more than 2 weeks after weaning from the LVAS (recovered group), while 9 could not be weaned or died within 2 weeks after weaning (unrecovered group). All patients were gradually weaned from the LVAS with adequate support for systemic circulation for 3 days. In the recovered group, indices of systolic time intervals (STIs) showed improvement within a week. However, improvement of STIs was slow reaching a plateau around the 10th day in the unrecovered group. On weaning from the LVAS, aortic systolic pressure and ejection time were regulated by the patients' own hearts and were nearly the same between the 2 groups. However, left atrial pressure was significantly higher in the unrecovered group than in the recovered group. These hemodynamic features were first present on the 7th day. Therefore, hemodynamic data on the 7th assistant day can be a reliable factor in predicting the possibility of successful weaning from the LVAS and recovery in patients with a failing heart.