Pericardial Effects on Diastolic Ventricular Interaction during Development

Abstract

ABSTRACT. The effects of the pericardium on myocardial diastolic ventricular interaction during early development were determined in vitro using hearts excised from eight preterm (109 f 0.106 SE d gestation; term = 147 d) and eight newborn (2.3 + 0.30 SE d postnatal age) lambs. The lamb hearts were excised with the pericardium intact and immersed in a cold cardioplegic solution. Subsequently, very compliant balloon catheters were inserted into the right and left ventricles retrograde through the pulmonary artery and aorta respectively. Before and after the removal of the pericardium, the changes in left ventricular pressure or volume caused by increasing right ventricular pressure or volume were measured. Computerized analysis of the pressure and volume recordings yielded pressure and volume transfer functions that quantified ventricular interaction. The pressure transfer functions (left ventricular pressure/right ventricular pressure) both with and without the pericardium intact were 0.297 f 0.010 SE and 0.140 f 0.005 SE, respectively, for the preterms and 0.650 + 0.033 S E and 0.301 f 0.031 SE for the newborns. The volume transfer functions (left ventricular volume/right ventricular volume) with and without the pericardium were 0.320 f 0.04 SE and 0.150 f 0.024 SE, respectively, for the preterm and 0.514 f 0.052 SE and 0.233 f 0.027 S E for the newborns. These data demonstrate that 1 ) the pericardium increases ventricular interaction in both preterm and newborn lambs and 2) the relative percentage increase is similar for both age groups and not age dependent. Furthermore, these findings suggest that the increase in ventricular interaction due to the presence of the pericardium is mediated by the relative compliances of the free walls, septum, and pericardium. through the myocardium, independent of neural, circulatory, or humoral effects, is termed ventricular interaction (1-3).Previous in vitro investigations have demonstrated age-related differences in diastolic ventricular interaction in the absence of the pericardium (4). These differences in interaction were attributed to a difference in the relative compliances of the interventricular septae between preterm and newborn lamb hearts. In a previous study (4), no difference was demonstrated between the free wall compliances of the right and left ventricular free walls of either group. The effect of the developing pericardium on ventricular interaction is not known. Studies of adult hearts enclosed by the pericardium and having a relatively more compliant right than left ventricular free wall have indicated that the pericardium enhances ventricular coupling (5-18). Furthermore, other adult studies suggest that the pericardium may grow or adapt to increased volume loads imposed on the myocardium (1 7, 19-2 1). Myocardial development may actually stimulate growth and affect endogenous characteristics of the pericardium (22-24). Therefore, it is reasonable to postulate that the pericardium may affect ventricular coupling in developing hearts and that these effec...

Cardiopulmonary interaction during partial liquid ventilation in surfactant-treated preterm lambs

“…The newborn's hypertrophied right ventricle and pericardial constraint may increase ventricular interdependence in our animals as compared to the series performed in the adult [34]. In addition, it has been shown that improved cardiac performance with increased intrathoracic pressure was limited to subjects in acute ventricular failure in whom afterload is the dominant determinant of cardiac function [38,39].…”

“…However, echocardiographic examination of the right ventricle is limited by the irregular shape, trabeculations of the walls, and the location of the right ventricle in the chest [14]. While measurements of the right ventricle would require a more invasive approach, the relatively high degree of ventricular interdependence at this age suggests that the right ventricle might respond in a similar fashion [34].…”

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