Influence of pericardium on ventricular mechanical interdependence in an isolated biventricular working pig heart model

The pericardium plays an important role in mechanical interactions between the right (RV) and left (LV) ventricles, referred to as ventricular interdependence. However, the exact mechanisms of its supportive role remain unknown. The present study aimed to evaluate specifically ventricular interdependence in a model of isolated biventricular working heart of large mammal, which is in absence of neurohormonal influence or series interactions, and to evaluate the impacts of intact pericardium on this phenomenon. Pig hearts were excised with the pericardium intact and connected to a biventricular working mode setup. Low and high ventricular preloads and afterloads were imposed on the hearts by changing independently the left (LA) and right (RA) atrial pressures, or the aortic (Ao) and pulmonary artery (PA) pressures, respectively, in the presence or absence of an intact pericardium. In the presence of the pericardium, increasing atrial pressures mainly impacted the ipsilateral ventricular haemodynamics, including an increase in ventricular outflow and end-diastolic pressures, independent of the contralateral atrial pressure. LV haemodynamics were also mainly altered by the increase in the ipsilateral afterload (Ao pressure). By contrast, RV haemodynamics, including the PA flow, were not only affected by increasing its ipsilateral (PA pressure), but also by its contralateral (Ao pressure) ventricular afterload. The preload but not afterload-dependent effects were abolished after removing the pericardium. Our work indicates that RV haemodynamics are highly impacted by the pericardiectomy. This highlights the requirement of keeping the pericardium intact to explore accurately cardiac haemodynamics, particularly in the RV. KEY POINTS: Pericardium has an important role in maintaining mechanical interventricular interaction, even if it is not essential for life. We used an ex vivo biventricular working pig heart model to explore intrinsic ventricular responses to independent variations of left and right preload and afterload, in the presence and absence of the pericardium. We show that, in the presence of the pericardium, the right ventricular haemodynamics is impacted by the ipsilateral preload as well as the ipsi- and contralateral afterloads, whereas the left ventricular haemodynamics is only impacted by its ipsilateral pre- and afterload. The preload but not afterload-dependent effects are abolished after removing the pericardium. These results demonstrate a critical function of the pericardium in maintaining RV haemodynamics, as well as preload-dependent ventricular interactions.