Right ventricular free wall stress after tricuspid valve annuloplasty in acute ovine right heart failure.

Abstract

Tricuspid annuloplasty rings may have a direct impact on right ventricular shape and free wall stress, potentially affecting chamber remodeling and recurrent regurgitation. In an acute model of ovine right heart failure, we investigated right ventricular free wall stress after annuloplasty with different prostheses. Thirty-xix sheep underwent implantation of sonomicrometry crystals on the tricuspid annulus and right ventricle. Each group consisted of 9 animals that received a flexible (28 ± 1 mm), rigid (29 ± 1 mm), or flexible-rigid hybrid (28 ± 1 mm) ring. Nine control animals had no ring implanted. Hemodynamic, sonomicrometry, and echocardiographic data were collected before (baseline-control group) and during acute right heart failure (control and ring groups). Free wall stress was calculated using the modified Laplace formula for thick shells. Ventricular geometry was determined from 3-dimensional crystal coordinates. Acute right heart failure reduced right ventricular deformation and fractional volume change while increasing pressure, tricuspid regurgitation grade, cross-sectional area, and free wall stress in control animals versus baseline. All rings significantly decreased right ventricular free wall stress versus control except rigid ring at end-systole. There was no significant difference in free wall stress or tricuspid regurgitation between any ring group during acute heart failure and baseline-control group. No significant difference in free wall stress was observed between any of the ring groups. Acute right heart failure significantly increased right ventricular free wall stress, which was normalized with equal efficacy by all studied prostheses. Chronic studies are needed to evaluate long-term effects of annuloplasty rings on right ventricle free wall stress and remodeling.