Pressure-volume loops: feasible for the evaluation of right ventricular function in an experimental model of acute pulmonary regurgitation?
Pressure-volume loop measurements by cardiac catheterization constitute a highly reliable method for the direct beat-to-beat functional analysis of the heart. We aimed to prove its feasibility for the instantaneous evaluation of right ventricular performance in a novel experimental model of pulmonary regurgitation (PR). Four-month-old sheep (n=18, weighing 35-45 kg) were operated via left anterior thoracotomy. A transannular patch (TAP) was sutured to the right ventricular outflow tract (RVOT). Pulmonary valve annulus was transsected through an incision over the patch without the need for cardiopulmonary bypass. Baseline right ventricular function was obtained by inserting conductance catheters through the pulmonary artery before and immediately after surgical induction of PR. All animals survived. Pressure-volume loop analysis presented immediate significant elevations in pressure and volume loading of the right ventricle. Maximum developed pressure incremented from 26.9±1.1 mmHg to 30.5±0.9 mmHg (P<0.01). End-diastolic volume [62.4±3.4-102.7±8.6 ml (P<0.01)] increased as well. Peak rate of pressure rise increased during ejection phase, and heart rate rose from 427.1±21.4 mmHg/s to 492.6±24.7 mmHg/s (P<0.01) and from 89.0±3.0/min to 93.0±3.3/min (P=0.04), respectively. Right ventricular ejection fraction decreased from 74.1±2.7% to 56.6±3.0% (P<0.01). Our results demonstrate that the conductance catheter method is feasible for the evaluation of acute right ventricular volume overload in this new model of PR with TAP augmentation of RVOT.