OBJECTIVES: Pulmonary hypertension (PHT) is associated with tricuspid annular 
dilatation, but the effect of acute increase of pulmonary pressure on 
three-dimensional (3D) tricuspid annular dynamics and shape is unknown. Better 
understanding of tricuspid annular dynamics may lead to improved and more 
durable surgical reparative techniques.
METHODS: In nine open-chest anaesthetized sheep nine sonomicrometry crystals 
were implanted on the right ventricle while on cardiopulmonary bypass. 
Additional nine crystals were implanted around the tricuspid annulus (TA) with 
one crystal at each commissure defining three separate annular regions: 
anterior, posterior and septal. Two additional equidistant crystals were 
implanted between each commissure, creating three segments for every region. 
Pressure transducers were placed in the left ventricular (LV), right ventricular 
(RV) and right atrium. PHT was induced by acute pulmonary artery constriction 
with a pneumatic occluder. Sonomicrometry and echocardiographic data were 
collected before and after induction of PHT. TA area, regional and total 
perimeter, and 3D annular geometry were calculated from 3D crystal coordinates. 
Regional annular contraction was defined as the percentage difference between 
maximal and minimal region length during the cardiac cycle.
RESULTS: PHT increased RV pressure from 31 ± 9 mmHg to 46 ± 13 mmHg (P = 0.001) 
and decreased left ventricular (LV) pressure from 111 ± 24 mmHg to 78 ± 36 mmHg 
(P = 0.018). There was no significant tricuspid regurgitation observed with PHT. 
During PHT, the TA area increased by 12 ± 13% from 641 ± 139 mm(2) to 721 ± 177 
mm(2) (P = 0.037). The total perimeter increased from 103 ± 11 mm to 109 ± 13 mm 
(P = 0.02). All annular regions dilated significantly with PHT with 8 ± 10, 5 ± 
5 and 5 ± 5% increase in anterior, posterior and septal annular length, 
respectively (P < 0.05). PHT reduced regional annular contraction in the 
anterior region only (17 ± 7 vs 14 ± 8%; P = 0.02). The TA had a complex 3D 
saddle geometry and the shape of the annulus was altered during PHT only in the 
antero-posterior region.
CONCLUSIONS: The changes in tricuspid annular conformation, contractility and 
its 3D geometry observed during acute ovine PHT may help in the design of new 
pathology-specific tricuspid annular rings.