Left ventricular heart failure model for testing cardiac assist devices

During the development of a new circulatory support system, we have used different animal models with and without heart failure for hemodynamic testing. As the normally functioning heart does not always allow for proper evaluation of a circulatory support system, a good and adjustable animal heart failure model is needed. The aim of the study was to develop a left ventricular failure model in calves for acute hemodynamic studies. The principle is based on the negative inotropic effect of drugs with bypass of the right ventricle. Seven calves were used in the study. Metoprolol and verapamil were both given intravenously as a bolus, and verapamil was continued as an infusion. The animals were equipped with a VVI pacemaker to treat the expected arteriovenous blockade. A centrifugal pump provided an adjustable flow with a two-stage inflow cannula draining both the upper and lower caval veins and with the outflow cannula in the pulmonary artery. The pump counteracted the effects of right ventricular failure and enabled us to increase the left atrial pressure to more than 20 mm Hg. Pressure in the left atrium rose from 5+/-3 to 25+/-4 mm Hg (p < 0.001), the left ventricular diastolic pressure increased from 2+/-3 to 17+/-7 mm Hg (p = 0.003), and the mean pulmonary pressure increased from 17+/-5 to 33+/-5 mm Hg (p < 0.001). Cardiac output was not significantly changed from 4.0+/-0.8 L/min in the healthy animals to 3.5+/-0.5 L/min (p = 0.25) in failure. The model allowed us to create an adjustable and isolated left ventricular failure well suited for short-term hemodynamic testing of a left ventricular support device.