Influence of an extracorporeal artificial ventricle on native ventricular performance.
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Hemodynamic and ventricular energetic parameters were measured in calves implanted with the air driven Utah Ventricular Assist Device (UVAD). Uptake site was varied to determine the effect of control mode and vacuum augmentation of filing. Uptake was drawn solely from the left atrium or combined with a left ventricular apical vent. LVAD outflow returned to the descending, thoracic aorta. Control modes examined included asynchronous pumping as well as 1:1 and 1:2 synchronous diastolic counterpulsation. The 85cc LVAD, vacuum formed from PELLETHANE, was implanted acutely in four animals and chronically in six (7, 49 and 116 days paracorporeally, 1, 28 and 32 days intrathoracically). Instantaneous blood pressures, intramyocardial pressure, aortic outflow, oxygen consumption, LVAD output and drive parameters were recorded. LVAD output was independent of control mode when the natural heart rate was greater than or equal to 80 beats per minute. Intrathoracically positioned LVADs pumped a mean flow of approximately equal to 5 liters/min without vacuum augmentation of filling. Paracorporeally positioned LVADs pumped approximately equal to 3 liters/min mean flow without vacuum augmentation and up to approximately equal to 6 liters/min with 38 mm Hg of vacuum augmentation of filling. Instantaneous ascending aortic pressure and flow showed distinct beat-to-beat variation depending on LVAD control mode. Lower average ventricular afterload was observed when pumping the LVAD asynchronously or 1:2 synchronously. In one acute preparation, left ventricular myocardial oxygen consumption was reduced from the unassisted average control level by 37% for the asynchronous and 1:1 synchronous control modes with left atrial uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
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After nearly 25 years of continuous technological development, the therapeutic arsenal for treating severe cardiac failure has been reinforced by the addition of a new weapon: a mechanical bridge whilst waiting for emergency cardiac transplantation for patients in cardiogenic shock and an alternative to transplantation in certain categories of chronic disease. The author describes the system and the results in the indication of a bridge to transplantation and the problems posed by the indication of chronic cardiac failure are discussed.
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Right ventricular balloon pumping (RVBP), i.e., using a balloon inserted into the right ventricular cavity to expel the blood into the pulmonary artery, was developed in this study. The balloon, which had an unstretched volume of approximately 15 ml, was made of polyurethane. In this experiment the balloon was inserted into the right ventricle via the right auricle or the apical area of the right ventricle. It was found that even when the natural heart was not beating, the pulmonary arterial blood flow could be maintained above 80 ml/min . kg body weight and the central venous pressure could be kept normal by combining RVBP and LVA. When the natural heart was beating but weak, the amount of increase of the pulmonary arterial blood flow induced by the application of RVBP depended on the degree of right heart failure, but RVBP could supply a sufficient flow rate to compensate for the failure of the right ventricle. Regurgitation through the tricuspid valve was scarcely ever found during RVBP.