Final answer:
Excessive intrapericardial pressure compared to RV diastolic pressure can lead to collapse of the RV wall during diastole due to the disruption in ventricular filling, linked to the isovolumic ventricular relaxation phase.
Step-by-step explanation:
When the intrapericardial pressure exceeds the diastolic pressure in the right ventricle (RV), it can lead to the collapse of the RV free wall during diastole. During the isovolumic ventricular relaxation phase, which is the initial phase of ventricular diastole, the pressure within the ventricles falls below that of the pulmonary trunk and aorta, prompting the semilunar valves to close and creating the dicrotic notch on blood pressure tracings. In contrast, during ventricular systole, the ventricular ejection phase occurs once ventricular pressure exceeds that of the pulmonary trunk and aorta, resulting in the expulsion of blood from the heart and a subsequent decrease in ventricular volume to the end systolic volume (ESV).
Understanding this dynamic helps to explain why excessive intrapericardial pressure can inhibit the normal filling of the RV during diastole, as the external pressure counteracts the lower pressure within the relaxed ventricle, preventing it from accepting incoming blood efficiently.