It has been suggested that pulsatile blood flow is superior to continuous flow in cardiopulmonary bypass (CPB). However, adoption of pulsatile flow (PF) technology has been limited due to practically and complexity of creating a consistent physiologic pulse. A pediatric pulsatile rotary ventricular pump (PRVP) was designed to address this problem. We evaluated the PRVP in an animal model, and determined its ability to generate PF during CPB. The PRVP (modified peristaltic pump, with tapering of the outlet of the pump chamber) was tested in 4 piglets (10-12kg). Cannulation was performed with right atrial and aortic cannulae, and pressure sensors were inserted into the femoral arteries. Pressure curves were obtained at different levels of flow and compared with both the animal's baseline physiologic function and a continuous flow (CF) roller pump. Pressure and flow waveforms demonstrated significant pulsatility in the PRVP setup compared to CF at all tested conditions. Measurement of hemodynamic energy data, including the percent pulsatile energy and the surplus hydraulic energy, also revealed a significant increase in pulsatility with the PRVP (p <0.001). PRVP creates physiologically significant PF, similar to the pulsatility of a native heart, and has the potential to be easily implemented in pediatric CPB.
Background Centrifugal pumps are increasingly used for temporary mechanical support for the treatment of cardiogenic shock. However, centrifugal pumps can generate excessive negative pressure and are afterload-sensitive. A previously developed modified roller pump mitigates these limitations both in vitro and in preliminary animal experiments. We report the results of intermediate-term testing of our evolving pump technology, known as BioVAD. Methods The BioVAD was implanted in 6 adult male sheep (62.5 ± 3.9 kg), with drainage from the left atrium and reinfusion into the descending aorta. The sheep were monitored for 5 days. Heparin was given during the initial implantation, but no additional anti-coagulation was given. Data collected included hemodynamic status, pump flow and pressures, laboratory values to monitor end-organ function and hemolysis, pathologic specimens to evaluate for thromboembolic events and organ ischemia, and explanted pump evaluation. Results All animals survived the planned experimental duration and there were no pump malfunctions. Mean BioVAD flow was 3.57 ± 0.30 L/min (57.1 cc/kg/min) and mean inlet pressure was -30.51 ± 4.25 mmHg. Laboratory values, including plasma free hemoglobin, creatinine, lactate, and bilirubin levels, remained normal. Three animals had small renal cortical infarcts, but there were no additional thromboembolic events or other abnormalities seen on pathologic examination. No thrombus was identified in the BioVAD blood flow path. Conclusions The BioVAD performed well for five days in this animal model of temporary left ventricular assistance. Its potential advantages over centrifugal pumps may make it applicable for short-term mechanical circulatory support.
Lung disease in children often results in pulmonary hypertension and right heart failure. The availability of a pediatric artificial lung (PAL) would open new approaches to the management of these conditions by bridging to recovery in acute disease or transplantation in chronic disease. This study investigates the efficacy of a novel PAL in alleviating an animal model of pulmonary hypertension and increased right ventricle afterload. Five juvenile lambs (20-30 Kg) underwent PAL implantation in a pulmonary artery to left atrium configuration. Induction of disease involved temporary, reversible occlusion of the right main pulmonary artery. Hemodynamics, pulmonary vascular input impedance, and right ventricle efficiency were measured under (A) baseline, (B) disease, and (C) disease+PAL conditions. The disease model altered hemodynamics variables in a manner consistent with pulmonary hypertension. Subsequent PAL attachment improved pulmonary artery pressure (p=0.018), cardiac output (p=0.050), pulmonary vascular input impedance (Z.0 p=0.028, Z.1 p=0.058), and right ventricle efficiency (p=0.001). The PAL averaged resistance of 2.3±0.8 mmHg/L/min and blood flow of 1.3±0.6 L/min. This novel low-resistance PAL can alleviate pulmonary hypertension in an acute animal model and demonstrates potential for use as a bridge to lung recovery or transplantation in pediatric patients with significant pulmonary hypertension refractory to medical therapies.
Purpose of Study: Availability of mechanical circulatory support of both sides of the heart for pediatric patients has been limited due to size constraints. By combining 2 scaled down ventricular assist devices (VADs), one centrifugal and one axial, into a single compact BiVAD unit, it is possible that a full heart replacement will be able to fit into pediatric patients. Methods Used: A scaled-up model of the final design has been constructed with some modifications to test the centrifugal pump and compatibility of the combination. A previously developed VAD was used as an inner axial pump. The outer pump consisted of a centrifugal pump using a slice motor design. A copper wound cast iron armature surrounded the housing, and drove permanent magnets in the pump rotor base. The pump housing and rotor were made using SLA 3D printing. The coils were driven by an RC speed controller and battery. The centrifugal pump's performance was tested using a closed loop of water. A clamp provided resistance, differential pressure was measured by a pressure sensor, and flow rate was measured using a clamp-on ultrasonic flow meter. Results: Tests show the centrifugal pump, which will support the left ventricle, generates 63-67 mmHg pressure increase at 0.5-5 L/min of flow at 1500 rpm. The axial pump, which will support the right ventricle generates 10-25 mmHg at 0.5-5 L/min of flow. Figure 1 shows the BiVAD configuration. Summary: The testing of a scaled up centrifugal pump showed promising results. In addition, the incorporation of the axial pump has allowed preliminary testing of the BiVAD system. Future work will focus on the miniaturization and levitation of the device.
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