Acute left ventricular unloading in chronic ovine biventricular failure with functional tricuspid regurgitation.

OBJECTIVES

Right ventricular failure and functional tricuspid regurgitation are associated with left ventricular assist device implantation. We set out to investigate the effect of acute left ventricular unloading on right ventricular subvalvular geometry in the setting of ovine biventricular heart failure with functional tricuspid regurgitation.

METHODS

Seven adult Dorset male sheep underwent left thoracotomy and pacemaker implantation and were paced until the development of biventricular dysfunction and functional tricuspid regurgitation. Subsequently, animals underwent sternotomy and cardiopulmonary bypass for implantation of sonomicrometry crystals around the tricuspid annulus, on each papillary muscle tip, and on the right ventricular epicardium. After weaning from cardiopulmonary bypass, a continuous-flow left ventricular assist device was implanted. Simultaneous hemodynamic, sonomicrometry, and echocardiographic data were acquired before and after full left ventricular unloading.

RESULTS

Pacing resulted in a significant increase in left ventricular end-diastolic dimension, tricuspid annular size, and tricuspid and mitral regurgitation. There was a significant reduction in left ventricular ejection fraction (60% ± 6% vs 34% ± 11%, P = .002) and right ventricular fractional area contraction (56% ± 8% vs 38% ± 12%, P = .001). During left ventricular unloading, inter-papillary muscle distances and papillary muscle area increased without changes in the distance of each papillary muscle tip to tricuspid annular plane. The septal region of the tricuspid annulus tended to increase during unloading. Tricuspid regurgitation did not change during left ventricular assist device unloading.

CONCLUSIONS

Left ventricular unloading in an ovine model of biventricular failure with tricuspid regurgitation was associated with increased inter-papillary distances and papillary muscle area most likely due to septal shift. These geometric alterations in subvalvular geometry may contribute to valvular insufficiency and right ventricular failure over time.