Tricuspid valve mechanics: understanding the effect of annular dilatation and papillary muscle displacement

Tricuspid regurgitation (TR), back flow of blood from the right ventricle to the right atrium, has been reported in approximately 85% of the population, with 16% having mild or severe TR. Patients with untreated moderate to severe TR are likely to experience decreased exercise capacity and have increased morbidity and mortality, thus affecting the patient's quality of life. Current methods of repair offer limited rates of success, and many patients require further operations to correct returning levels of TR. Incomplete repair may be due to incomplete understanding of the functional anatomy and mechanics of the TV and the underlying causes of TR. It was hypothesized that alterations in the geometry of tricuspid valve annular and subvalvular apparatus induced by ventricular dilatation determine the severity of TR. In vivo measurements of papillary muscle (PM) position in patients with single or biventricular dilatation revealed PM displacement away from the center of the annulus as compared to control patients. Additionally, pulmonary arterial pressure, annulus area, ventricular size and apical displacement of the anterior PM were highly correlated with the severity of TR. An in vitro right-heart simulator was developed to investigate isolated mechanics of TR. Through these in vitro studies it was demonstrated that the tricuspid valve begins to leak at only 40% dilation, much lower than the mitral valve. Additionally, it was shown that isolated PM displacement resulted in significant TR. The highest levels of TR were achieved with a combination of annular dilatation and PM displacement. Alterations in leaflet coaptation, as quantified by measuring the amount of leaflet available for coaptation and leaflet mobility were observed with annular dilatation and PM displacement, both isolated and combined. The changes in leaflet coaptation resulted in redistribution of the forces on the chords originating from the anterior PM and inserting into the anterior and posterior leaflets. The findings herein provide the clinical and scientific community with a mechanistic understanding of the tricuspid valve to further improve intervention and repair of TV disease.PhDCommittee Chair: Yoganathan, Ajit P.; Committee Member: Adams, David H.; Committee Member: Gleason, Rudoplh; Committee Member: Lerakis, Stamatios; Committee Member: Oshinski, John; Committee Member: Taylor, W. Rober

Correlates of Tricuspid Regurgitation as Determined by 3D Echocardiography: Pulmonary Arterial Pressure, Ventricle Geometry, Annular Dilatation, and Papillary Muscle Displacement

Background— While it is understood that annular dilatation contributes to tricuspid regurgitation (TR), other factors are less clear. The geometry of the right ventricle (RV) and left ventricle (LV) may alter tricuspid annulus size and papillary muscle (PM) positions leading to TR. Methods and Results— Three-dimensional echocardiographic images were obtained at Emory University Hospital using a GE Vivid 7 ultrasound system. End-diastolic area was used to classify ventricle geometry: control (n=21), isolated RV dilatation (n=17), isolated LV dilatation (n=13), and both RV and LV dilatation (n=13). GE EchoPAC was used to measure annulus area and position of the PM tips. Patients with RV dilatation had significant ( P ≤ 0.05) displacement of all PMs apically and the septal PM and posterior PM away from the center of the RV toward the LV. Patients with LV dilatation had significant ( P ≤0.05) apical displacement of the anterior PM. Pulmonary arterial pressure ( r =0.66), annulus area ( r =0.51), apical displacement of the anterior PM ( r =0.26), posterior PM ( r =0.49), and septal PM ( r =0.40), lateral displacement of the septal PM ( r =0.37) and posterior PM ( r =0.40), and tenting area and height ( r =0.54, 0.49), were significantly ( P ≤0.05) correlated to the grade of TR. Ventricle classification ( r =0.46) and RV end-diastolic area ( r =0.48) also were correlated with the grade of TR. A regression analysis found ventricle classification ( P =0.001), pulmonary arterial pressure ( P ≤0.001) annulus area ( P =0.027), and apical displacement of the anterior PM ( P =0.061) to be associated with the grade of TR. Conclusions— Alterations in ventricular geometry can lead to TR by altering both tricuspid annulus size and PM position. Understanding these geometric interactions with the aim of correcting pathological alterations of the tricuspid valve apparatus may lead to more robust repairs

Correlates of Tricuspid Regurgitation as Determined by 3D Echocardiography: Pulmonary Arterial Pressure, Ventricle Geometry, Annular Dilatation, and Papillary Muscle Displacement

Background— While it is understood that annular dilatation contributes to tricuspid regurgitation (TR), other factors are less clear. The geometry of the right ventricle (RV) and left ventricle (LV) may alter tricuspid annulus size and papillary muscle (PM) positions leading to TR. Methods and Results— Three-dimensional echocardiographic images were obtained at Emory University Hospital using a GE Vivid 7 ultrasound system. End-diastolic area was used to classify ventricle geometry: control (n=21), isolated RV dilatation (n=17), isolated LV dilatation (n=13), and both RV and LV dilatation (n=13). GE EchoPAC was used to measure annulus area and position of the PM tips. Patients with RV dilatation had significant ( P ≤ 0.05) displacement of all PMs apically and the septal PM and posterior PM away from the center of the RV toward the LV. Patients with LV dilatation had significant ( P ≤0.05) apical displacement of the anterior PM. Pulmonary arterial pressure ( r =0.66), annulus area ( r =0.51), apical displacement of the anterior PM ( r =0.26), posterior PM ( r =0.49), and septal PM ( r =0.40), lateral displacement of the septal PM ( r =0.37) and posterior PM ( r =0.40), and tenting area and height ( r =0.54, 0.49), were significantly ( P ≤0.05) correlated to the grade of TR. Ventricle classification ( r =0.46) and RV end-diastolic area ( r =0.48) also were correlated with the grade of TR. A regression analysis found ventricle classification ( P =0.001), pulmonary arterial pressure ( P ≤0.001) annulus area ( P =0.027), and apical displacement of the anterior PM ( P =0.061) to be associated with the grade of TR. Conclusions— Alterations in ventricular geometry can lead to TR by altering both tricuspid annulus size and PM position. Understanding these geometric interactions with the aim of correcting pathological alterations of the tricuspid valve apparatus may lead to more robust repairs

In Vitro Characterization of the Mechanisms Responsible for Functional Tricuspid Regurgitation

Background—Functional tricuspid regurgitation (TR) is increasingly recognized as a source of morbidity. Current repair strategies focus on annular remodeling because annular dilatation is common in patients with TR. Although papillary muscle (PM) displacement is recognized in functional mitral regurgitation, its role in TR is less well characterized. The objective of this in vitro study was to further clarify the mechanisms by which TR occurs as an effect of annular dilatation and PM displacement. Methods and Results—Porcine tricuspid valves (n=16) were studied in an in vitro right heart simulator. The valve dynamics were quantified with isolated annular dilatation starting with a normal annular size (6 cm2) and incrementally dilated up to 100%, isolated PM displacement, and a combination of the 2. All valves lost competence at 40% dilatation, resulting in a TR of 7.9±3.4 mL (P≤0.05) compared with baseline and central residual leaflet length of 0.5±0.2 cm. Multidirectional displacement of the anterior and..