[Experimental study of effect on lung in pig supported with RVAD]

Ventricular assist device (VAD) has a potent assist effect in the treatment of severe cases of acute heart failure, exhibiting excellent results at present. Right ventricular assist device (RVAD) has a potent flow volume assist effect in severe right heart failure, but in possibly induces aggravation because of pulmonary function disturbance, left heart failure, etc, since it supplies blood to the low-pressure pulmonary circulation system. However, its assist effects and drawbacks have not yet been examined sufficiently. These points, an acute experiment was performed on the effect of RVAD-induced changes in assist flow volume on hemodynamic changes and the lungs. Pulmonary arterial trunk of pigs weighting 40 +/- 3.4 kg were strangulated to obtain right heart failure models of pulmonary arterial blood flow reduced to about 60%. RVAD was then set to run on the models at a fixed rate (100 beats/min, S/D 35%). The models with RVAD flow about 30% of Ao flow were defined as Group I (low flow assist group: N = 9) and those with RVAD flow about 60% of Ao flow were defined as Group II (high flow assist group: N = 9), and results were compared between both groups. RVAD showed remarkable right ventricular preload relieving effect in both groups. The left cardiac function in Group II after 3 hours of RVAD run differed significantly from Group I in LVRDF, LAP, AoP, and Ao flow, and tended to aggravate them when the left cardiac function was reduced. Pulmonary function changes in Group II in terms of PaO2, PaCO2, SaO2, and A-aDO2 change rates suggested retention to some extent of gas exchange capacity and gradual decrease in gas diffusion capacity. In Group II after 3 hours of RVAD run, pulmonary extravascular thermal volume increased significantly, ACE levels decreased significantly, and the lungs presented morphologically high-level edematous changes, suggesting the possible damage to the lung physiological function in Group II. It was considered that excess flow volume assist during right ventricular assist alone may possibly induce left heart failure and that the assist volume should be decided carefully with attention paid to the left ventricular and pulmonary function.