Background and aim:

Right-ventricular (RV) failure secondary to RV volume or pressure overload is frequently encountered in patients with congenital heart disease. While left-ventricular (LV) failure is increasingly well characterized, the functional and structural features of RV failure are currently insufficiently understood. In this study, we aimed to characterize the influence of experimentally induced pulmonary valve (PV) regurgitation (PR) on the RV morphology and function in a juvenile porcine animal model.

Methods:

One-month-old piglets underwent surgical PR induction. The animals were randomly assigned to the PR or the control group. After left-lateral thoracostomy and local opening of the pericardium, the PV cusps of the lateral hemi-circumference of the PV were attached to the pulmonary artery wall by external placement of plication sutures, thus creating PR. In control group animals, a sham procedure without placement of the plication sutures was conducted. After 10 weeks, the animals underwent cardiac magnetic resonance imaging (MRI) in order to objectify the degree of PR, static and dynamic measurements of the RV and the LV dimensions and functions, respectively. These parameters were compared between PR group and control group animals.

Results:

12 piglets (weight 15±2.5kg) were included in the experiment. 4 animals died, thereof 2 (1 PR group, 1 control group) because of immediate perioperative RV failure, 1 (PR group) because of ventricular arrhythmia after central line placement and 1 (control group) due to pulmonary infection 9 days postoperatively. The remaining 8 animals (PV group n=5, control group n=3) underwent MRI after a median of 70±2days with a median weight of 47±7.9kg. The PR group showed a significantly increased RV stroke volume (95±20 vs. 64±13ml; p=0.041) and pulmonary valve regurgitation fraction (23±17 vs. 0.3±0.02%; p=0.031) compared with the control group. The mean gradient over the PV was higher in the PR compared with the control group (2.9±0.6 vs. 1.1±0.3mmHg; p=0.002). The RV enddiastolic volume (PR:130±21ml, control:87±16ml; p=0.012), endsystolic volume (PR:35±10ml, control:23±2.4ml; p=0.043) and myocardial mass (PR:34±4g, control:23±4g; p=0.05) were increased in the PR group, while the RV ejection fractions were comparable in both groups (PR:73±8% control:73±3%; p=0.046). Circumferential Of note, the differences in in RV volumes were not adequately reflected by the RV enddiastolic (PR:33±7mm, control:28±6mm; p=0.19) and endsystolic (PR:13±3mm, control:10±1.6mm; p=0.14) diameters. The left-ventricular and left- and right-atrial parameters did not differ between the groups.

Conclusions:

Despite high vulnerability in this young animal model, the model results in reproducible induction of PR and RV volume overload. The effects can be objectified using cardiac MRI.