Chronic In Vivo Test of a Right Heart Replacement Blood Pump for Failed Fontan Circulation

Abstract

An implantable rotary blood pump was developed to provide long-term mechanical right heart support for patients who have failing Fontan circulation. The objective of this study was to evaluate the pump in vivo in a 30 day sheep study. Pump speed was set at 3,900 rpm for the duration of the study, and pump power was between 4.3 and 4.6 W. The pump inlet pressures for the superior vena cava (SVC) and inferior vena cava (IVC) were 14 ± 15 and 11 ± 15 mm Hg, respectively, over the duration of the study. Hematocrit remained stable at 30% ± 4%. Partial thromboplastin time (PTT) steadily increased from 30 s preoperatively to a high of 59 s on postoperative day 20, while prothrombin time (PT) remained at 20 ± 2 s for the duration of the study. The implantation and postoperative recovery were successful, and the animal demonstrated normal physiologic pulmonary and venous pressures and cardiac output. On pump inspection, the IVC and SVC inlets were completely clear of any deposits, but there were small thrombi (approximately 0.5 mm diameter) between each of the three rotor blades and along 20% of the parting line of the two volute halves. A complete right heart bypass was performed, postoperative recovery was successful, and the pump demonstrated adequate circulatory support and normal physiologic pulmonary and venous pressures. This study was the first successful test of a right heart replacement device in a chronic animal study.

Review on Mechanical Support and Cell-Based Therapies for the Prevention and Recovery of the Failed Fontan-Kreutzer Circulation

“…Several groups have identified the need for a mechanical assist device that does not assist the systemic ventricle in hopes of improving CVP, but rather is implanted in the central venous system. All groups (Table 2) tested these devices in an in vitro system, with tunable capacitance and resistance, representative of Fontan physiology (65, 67,69,70). The largest in vitro change in pressure (7.6 mmHg) was found by Rodefeld et al using a derivative of the Von Karman viscous rotary pump (Table 2) (66,67).…”

“…A group out of Penn State College of Medicine performed both in vitro and in situ experimentation of a venous assist device placed at the four way junction of the PA, IVC, and SVC (70). The in vitro work delivered promising results with an inverse relationship between pressure head and flow (70).…”

“…A group out of Penn State College of Medicine performed both in vitro and in situ experimentation of a venous assist device placed at the four way junction of the PA, IVC, and SVC (70). The in vitro work delivered promising results with an inverse relationship between pressure head and flow (70). The authors then implanted their device in a single sheep model for 30 days; post-operative complications included pressure catheter migration from the PA to the RV, edema, and increased levels of thromboplastin, a protein responsible for initiating blood coagulation (70).…”

“…The in vitro work delivered promising results with an inverse relationship between pressure head and flow (70). The authors then implanted their device in a single sheep model for 30 days; post-operative complications included pressure catheter migration from the PA to the RV, edema, and increased levels of thromboplastin, a protein responsible for initiating blood coagulation (70). The explant data revealed a severely bent outlet cannula with multiple thrombi present and thrombus formation on the outlet rotor (70).…”

“…The authors then implanted their device in a single sheep model for 30 days; post-operative complications included pressure catheter migration from the PA to the RV, edema, and increased levels of thromboplastin, a protein responsible for initiating blood coagulation (70). The explant data revealed a severely bent outlet cannula with multiple thrombi present and thrombus formation on the outlet rotor (70). This study confirms the importance of device testing in a large animal model with Fontan circulation for a better understanding of design needs and in situ function.…”