Ovine tricuspid annular dynamics and three-dimensional geometry during acute atrial fibrillation

Long-standing atrial fibrillation (AF) may lead to tricuspid regurgitation (TR) and right ventricular dysfunction. However, the effect of acute AF on tricuspid annular (TA) dynamics and three-dimensional geometry is unknown.

In eight adult sheep, sonomicrometry crystals were implanted around the tricuspid annulus and right ventricular free wall. Pressure transducers were placed in the right ventricle, left ventricle, and right atrium. After weaning from cardiopulmonary bypass and a period of hemodynamic stabilization, simultaneous sonomicrometry and hemodynamic data were collected in sinus rhythm (SR) and during experimental AF (400b/min right atrial pacing). Annular area, perimeter, dimensions, height, global and regional annular contraction, and strain were calculated based on cubic spline fits to crystal 3D locations.

Maximal TA area increased from 1084.9±273.9mm2 in SR to 1207.5±322.1mm2 during AF (p = 0.002). Anteroposterior diameter increased from 36.5±5.0mm to 38.4±5.5mm (p = 0.05). TA contraction decreased from 7±2% in SR to 2±1% in AF (p = 0.001). Anterior, posterior, and septal regional annular contraction decreased from 10±4%, 8±3% and 6±2% to 4±2%, 3±1% and 2±1% for SR and AF, respectively (p<0.05). AF perturbed systolic global annular strain (from -6.52±1.74% to -2.78±1.79%; p = 0.003) and caused annular stretch. Annular height marginally decreased with AF from 5.8±1.9mm to 5.7±2.0mm; p = 0.039.

Acute experimental AF in healthy sheep was associated with TA dilation, flattening, and decreased total and regional annular contractility. These data may help elucidate the pathophysiology of functional TR associated with AF.