Pericardial modulation of right and left ventricular diastolic interaction
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The right ventricle and pericardium significantly impact left ventricular diastolic pressure-volume relations. Pericardial tightness amplifies the right ventricle's influence on left ventricular chamber stiffness.
Area of Science:
- Cardiovascular Physiology
- Cardiac Mechanics
Background:
- Understanding the interplay between cardiac chambers and surrounding structures is crucial for diagnosing and treating heart conditions.
- The pericardium's role in modulating ventricular diastolic function requires further elucidation.
Purpose of the Study:
- To investigate the effects of right ventricular (RV) filling and pericardial integrity on left ventricular (LV) diastolic pressure-volume (P-V) relationships.
- To quantify the influence of the pericardium on RV-LV diastolic interactions.
Main Methods:
- Isolated blood-perfused dog heart model with controlled heart rate and coronary perfusion pressure.
- Stepwise increases in RV filling pressure with intact and altered pericardial conditions.
- Direct control of LV volume via an intraventricular balloon to assess diastolic P-V curves.
Main Results:
- Increased RV filling pressure shifted LV diastolic P-V relations upward and leftward, indicating increased LV chamber stiffness when the pericardium was intact.
- Suturing pericardial incisions exacerbated this leftward shift, highlighting the effect of pericardial tightness.
- In the absence of the pericardium, RV filling had minimal impact on LV diastolic P-V relations except at very high RV pressures.
Conclusions:
- The pericardium exerts a significant influence on LV diastolic P-V relations, particularly at elevated RV filling pressures.
- Pericardial tightness modulates the impact of the right ventricle on left ventricular diastolic function.
- These findings underscore the importance of pericardial integrity in maintaining normal diastolic mechanics.
Abstract:
We studied the effects of the right ventricle (RV) and pericardium on left ventricular (LV) diastolic pressure-volume (P-V) relations in the normothermic isolated blood-perfused dog heart. Studies were performed at a constant heart rate (atrial pacing at 120 beats/min) with a coronary perfusion pressure of 100 mm Hg. LV volume was directly controlled by an intraventricular balloon, whereas RV filling pressure was increased stepwise from zero to 20 mm Hg. During progressive increases in RV filling pressure, with the pericardium intact, the LV diastolic P-V relations were shifted up and to the left; this leftward shift of the LV diastolic P-V relation was associated with an increase in the modulus of LV chamber stiffness. Closing the small pericardial incisions with sutures significantly increased this effect. In the absence of the pericardium, progressive filling of the RV resulted in minor changes in LV diastolic P-V relations. Only when the RV filling pressure was markedly elevated (20 mm Hg) was there a significant effect on LV diastolic pressure. The pericardium has a small but significant effect on LV diastolic P-V relations at physiological RV filling pressures, and this effect becomes considerable at high RV filling pressures. The RV influence on LV diastolic P-V relations is significantly modulated by the presence of tightness of the pericardium.