ObjectiveAn out-thoracic paraaortic counterpulsation device(PACD) developed in the Reseach Center of our hospital was evaluated for its hemodynamic effects in an animal model with induced acute heart failure.MethodsEight healthy adult sheep with a weight of 38.5 to 54.5 kg were used as models for acute heart failure by snaring branches of coronary arteries.Thoracotomy was performed through the space under the left 4th rib.A Satinski clamp was used for partially clamping the descending aorta, and the Dacron vascular graft of out-thoracic PACD was sutured end-to-side to the descending aorta.The out-thoracic PACD used in this study had a blood chamber that was separated from the gas chamber by a movable polyurethane membrane .A stroke volume of 60 ml could be pumped when it was fully inflated.A 4F multipurpose catheter was inserted through the left ventricular apex for measuring and recording left ventricular pressures.A standard 40-ml intraaortic balloon was inserted into the descending aorta via the surgically exposed left femoral artery.Baseline hemodynamic data were collected after the model for acute heart failure was created without mechanical support.Mechanical support was randomly initiated either by the IABP or by the out-thoracic PACD in each experimental phase.Both devices were driven by the same console and synchronization with electrocardiogram was performed.Hemodynamic indexes and left carotid artery flow were calculated at baseline (device off) and during the period of 1 : 2 support for the 60-ml out-thoracic PACD and 40-ml IABP in the same animal.Baseline and support modes for devices were maintained for 15 minutes individually to ensure that a steady-state was achieved.ResultsBoth out-thoracic PACD and IABP resulted in a increase in the cardiac output (17.79％ with out-thoracic PACD vs.13.46％ with IABP, P =0.803) and the mean diastolic aortic pressure (29.48％ with out-thoracic PACD vs.15.01％ with IABP, P = 0.001).The use of out-thoracic PACD also led to a greater reduction in left ventricular end-diastolic pressure (35.09％ with out-thoracic PACD vs.15.79％ with IABP, P = 0.004).Meanwhile the out-thoracic PACD increased left carotid artery flow (14.52％ with out-thoracic PACD vs.6.70％ with IABP, P =0.006).No evidence of hemolysis, thrombus formation or major organ injury was identified during the experiment.ConclusionThe study indicated that a 60-ml out-thoracic PACD, which providing an improved mechanical circulatory support, was superior to a 40-ml IABP in the setting of experimental acute heart failure.This device may be used as a desirable alternative for the long-term mechanical support in patients with severe heart failure or those waiting for a heart transplantation, owing to its properties of low cost,easily to be implanted and removed, as well as a high biocompatibility.