Low-flow support of the chronic pressure-overloaded right ventricle induces reversed remodeling

Background: Mechanical right ventricular (RV) support in pulmonary arterial hypertension patients has been feared to cause pulmonary hemorrhage and to be detrimental for the after-load-sensitive RV. Continuous low-flow pumps offer promise but remain insufficiently tested.

Methods: The pulmonary artery was banded in 20 sheep in this study. Eight weeks later, a Synergy micro-pump (HeartWare International, Framingham MA) was inserted in 10 animals, driving blood from the right atrium to the pulmonary artery. After magnetic resonance imaging, hemodynamics and RV pressure-volume loop data were recorded. Eight weeks later, RV function was assessed in the same way, followed by histologic analysis of the ventricular tissue.

Results: During the 8 weeks of support, RV volumes and central venous pressure decreased significantly, whereas RV contractility increased. Pulmonary artery pressure increased modestly, particularly its diastolic component. RV contribution to total right-sided cardiac output increased from 12 ± 12% to 41 ± 9% (p < 1 × 10^-4). After pump inactivation, and compared with 8 weeks earlier, RV volumes had significantly decreased, tricuspid valve regurgitation had almost disappeared, and RV contractility had significantly increased, resulting in significantly increased RV forward power (0.25 ± 0.05 vs 0.16 ± 0.06 W, p = 0.014). Fulton index and RV myocyte size were significantly smaller, and without changes in fibrosis, when compared with controls.

Conclusions: Prolonged continuous low-flow RV mechanical support significantly unloads the chronic pressure-overloaded RV and improves cardiac output. After 8 weeks, RV hemodynamic recovery and reverse remodeling begin to occur, without increased fibrosis.