Effect of variable annular reduction on functional tricuspid regurgitation and right ventricular dynamics in an ovine model of tachycardia-induced cardiomyopathy.

OBJECTIVE: To investigate the effect of variable tricuspid annular reduction (TAR) on functional tricuspid regurgitation (FTR) and right ventricular (RV) dynamics in ovine tachycardia-induced cardiomyopathy. METHODS: Nine adult sheep underwent implantation of a pacemaker with an epicardial lead and were paced at 200 to 240 bpm until the development of biventricular dysfunction and functional TR was noted. During reoperation on cardiopulmonary bypass, 6 sonomicrometry crystals were placed around the tricuspid annulus (TA) and 14 were placed on the RV epicardium. Annuloplasty suture was placed around the TA and externalized to an epicardial tourniquet. After weaning from cardiopulmonary bypass, echocardiographic, hemodynamic, and sonomicrometry data were acquired at baseline and during 5 progressive TARs achieved with suture cinching. TA area and RV free wall strains and function were calculated from crystal coordinates. RESULTS: After pacing, changes in left ventricular (LV) ejection fraction and RV fractional area decreased significantly. Mean TA diameter increased from 25.1 ± 2.9 mm to 31.5 ± 3.3 mm (P = .005), and median TR (range, 0-3+) increased from 0 (0) to 3 (2) (P = .004). Progressive suture cinching reduced the TA area by 18 ± 6%, 38 ± 11%, 56 ± 10%, 67 ± 9%, and 76 ± 8%. Only aggressive annular reductions (67% and 76%) decreased TR significantly, but these were associated with deterioration of RV function and strain. A moderate annular reduction of 56% led to a substantial reduction of TR with little deleterious effect on regional RV function. CONCLUSIONS: A moderate TAR of approximately 50% may be most advantageous for correction of functional TR and simultaneous maintenance of regional RV performance. Additional subvalvular interventions may be needed to achieve complete valvular competence.

The influence of tricuspid annuloplasty prostheses on ovine annular geometry and kinematics.

BACKGROUND: Surgical repair of functional tricuspid regurgitation is centered on annular reduction with artificial rings; however, the precise effect of prosthesis implantation on annular geometry, dynamics, and strain is unknown. METHODS: Forty healthy sheep had sonomicrometry crystals implanted around the tricuspid annulus and onto right ventricle free wall. Ten animals underwent tricuspid annuloplasty with a flexible Duran AnCore ring (Medtronic, Minneapolis, Minn) (28 ± 1 mm), 10 with Contour 3D rigid ring (Medtronic) (29 ± 1 mm), 10 with hybrid Tri-Ad Adams band (Medtronic) (28 ± 1 mm), and 10 had no prosthesis (control group). Pressure sensors were inserted in the left ventricle, right ventricle, and right atrium. Data were acquired with open chest after weaning off cardiopulmonary bypass and hemodynamic stabilization. Annular area, global and regional contraction, height, and strain were calculated based on cubic spline fits to crystal locations. RESULTS: Tricuspid annular area contraction during the cardiac cycle was 11% ± 3% in the control group. The Contour 3D ring significantly impaired annular contraction (2% ± 1%) whereas the Duran AnCore ring and Tri-Ad Adams band (9% ± 3% and 8% ± 4%, respectively) permitted dynamic area change. Global perimeter reduction was 6% ± 1% in the control group and decreased in the Duran AnCore (3% ± 1%), Contour 3D (0.4% ± 0.2%), and Tri-Ad Adams (3% ± 1%) groups (all P values < .001 vs control). Annular height was 6.2 ± 2.0 mm in the control group, unchanged in the Contour 3D (4.9 ± 1.1 mm) but reduced in the Duran AnCore (3.1 ± 1.3 mm) and Tri-Ad Adams (3.1 ± 1.0 mm) groups (P < .001 Duran AnCore and Tri-Ad Adams vs control). Rings perturbed systolic global annular strain (control, 5.3% ± 1.8%; Duran AnCore, 2.3% ± 1.0%; Contour 3D, 0.6% ± 0.2%; and Tri-Ad Adams, -2.6% ± 0.7%) with Contour 3D inducing the biggest change (P < .05 vs other groups). CONCLUSIONS: In healthy ovine hearts, flexible and hybrid rings better preserved annular dynamics and strain, whereas the rigid ring maintained 3-dimensional geometry. These data may aid the design of optimal tricuspid annular prostheses and improve durability of valve repair.

Impact of tricuspid annular size reduction on right ventricular function, geometry and strain.

OBJECTIVES: Restrictive tricuspid annuloplasty is a clinically accepted approach to treat functional tricuspid regurgitation. We set out to investigate the effect of varying degrees of tricuspid annular reduction on the right ventricular (RV) function, geometry and strain. METHODS: Eight, healthy sheep (45 ± 4 kg) had 6 sonomicrometry crystals implanted around the tricuspid annulus and 20 onto the epicardium of the right ventricle defining 3 free wall regions: basal, mid and lower. A polypropylene annuloplasty suture was placed around the tricuspid annulus and externalized to an epicardial tourniquet. Simultaneous echocardiographic, haemodynamic and sonomicrometry data were acquired at baseline and during 5 consecutive annular reduction steps (TAR 1-5) with successive (5-7 mm) suture cinching. RV free wall circumferential, longitudinal and areal cardiac and interventional strains, RV radius of curvature (ROC), cross-sectional area and tricuspid annular dimensions were calculated from 3-dimensional crystal coordinates. RESULTS: TAR 1-5 resulted in 19 ± 15%, 35 ± 15%, 51 ± 15%, 60 ± 15% and 68 ± 13% tricuspid annular area reduction, respectively. TAR 1 and 2 had minimal influence on the RV function, RV-ROC and strains. TAR 4 and 5 decreased RV-ROC in basal and mid-regions, but reduced the RV cross-sectional area change (from 19 ± 4% at baseline to 14 ± 3% and 13 ± 2%, respectively, P < 0.001) and circumferential and areal strains. TAR 3 significantly decreased free wall RV-ROC from 44.0 ± 1.5 to 42.6 ± 2.4 mm P < 0.001 at the RV base but maintained the regional ventricular function and strains. CONCLUSIONS: In healthy ovine hearts, a tricuspid annular area reduction of ∼50% provides optimal conditions for reducing RV-ROC while maintaining regional RV function and strain patterns.

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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Sonomicrometry-derived 3-dimensional geometry of the human tricuspid annulus.

OBJECTIVES: Surgical correction of functional tricuspid regurgitation is focused on prosthetic reduction and remodeling of the tricuspid annulus. We set out to investigate the precise geometry of the human tricuspid annulus to better guide surgical therapy. METHODS: Eleven human donor hearts with normal right ventricular function and without tricuspid regurgitation that were rejected for clinical transplantation were harvested. Sonomicrometry crystals were sewn around the tricuspid annulus and pressure sensors placed in the right ventricle and right atrium. The hearts were studied in the TransMedics Organ Care System (Andover, Mass) ex vivo perfusion apparatus in the right heart working model. Data were acquired at baseline and before and after bolus calcium infusion. Annular height, dimensions, strain, and curvature were calculated based on 3-dimensional crystal coordinates. RESULTS: Maximal annular area was 997 ± 258 mm2 and minimal 902 ± 257 mm2 with contraction of 10% ± 5% at baseline and 19% ± 6% after calcium (P = .007). Segmental contractility of anterior, posterior, and septal annular regions was 7% ± 5%, 6% ± 4%, and 6% ± 3%, respectively. Only anterior region had increased contractility after calcium infusion (to 15% ± 5%; P = .023). Annulus had its high points at anteroseptal commissure and the midposterior region and lowest point in the midseptal region with maximal and minimal height of 5.0 ± 1.1 mm and 4.0 ± 1.1 mm, respectively. The greatest curvature responsible for out of plane annular bending was observed at annular high points. CONCLUSIONS: The human tricuspid annulus is a complex 3-dimensional dynamic structure with its high points and maximal degree of bending at the anteroseptal commissure and midposterior annulus. These detailed geometric data may aid the design of more physiologic annular prostheses and surgical reparative techniques.

A fiduciary marker-based framework to assess heterogeneity and anisotropy of right ventricular epicardial strains in the beating ovine heart.

Quantifying ventricular deformation in health and disease is critical to our understanding of normal heart function, heart disease mechanisms, and the effect of medical treatments. Imaging modalities have been developed that can measure ventricular deformation non-invasively. However, because of the small thickness, complex shape, and anatomic position of the right ventricle, using these technologies to determine its deformation remains challenging. Here we develop a first fiduciary marker-based method to assess heterogeneity and anisotropy of right ventricular epicardial strain across the entire free wall. To this end, we combine a high-density array of sonomicrometry crystals implanted across the entire right ventricular epicardial surface with a subdivision surface algorithm and a large deformation kinematics framework. We demonstrate our approach on four beating ovine hearts and present a preliminary regional analysis of circumferential, longitudinal, and areal strain. Moreover, we illustrate maps of the same strains across the entire right ventricular epicardial surface to highlight their spatial heterogeneity and anisotropy. We observe in these animals that RV epicardial strains vary throughout the cardiac cycle, are heterogeneous across the RV free wall, and are anisotropic with larger compressive strains, i.e., contraction, in the longitudinal direction than in the circumferential direction. Average peak compressive strains vary by region between -3.34% and -8.29% in circumferential direction, and -4.02% and -10.57% in longitudinal direction. In summary, we introduce an experimental framework that will allow us to study disease- and device-induced deformations, and long-term consequences of these deformations, including heterogeneous and anisotropic effects.