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Mechanical interactions between four heart chambers with and without the pericardium in canine hearts
Insights
The pericardium significantly impacts heart chamber interactions and ventricular function, especially during simultaneous filling pressure increases. This finding is crucial for understanding heart disease, particularly acute heart failure.
Area of Science:
- Cardiovascular Physiology
- Cardiac Mechanics
- Biomedical Engineering
Background:
- Understanding mechanical interactions between heart chambers is vital for cardiac function.
- The role of the pericardium in modulating these interactions is not fully elucidated.
- Ventricular pressure-volume relationships are key indicators of cardiac performance.
Purpose of the Study:
- To investigate mechanical interactions among the four heart chambers.
- To determine the influence of the pericardium on these interactions.
- To analyze ventricular pressure-volume relationships under varying filling pressures.
Main Methods:
- Utilized excised postmortem mongrel dog hearts with intact pericardium.
- Inserted compliant balloons into all four heart chambers to control filling pressures.
- Measured right and/or left ventricular pressure-volume relationships under constant pressures in other chambers.
Main Results:
- Ventricular pressure-volume relationships were minimally affected by atrial pressure changes without the pericardium.
- Ventricular compliance decreased with increased opposing ventricular pressure.
- The pericardium significantly enhanced all investigated mechanical interactions, especially with elevated filling pressures.
Conclusions:
- The pericardium plays a critical role in modulating mechanical interactions between heart chambers.
- These interactions are amplified by the pericardium when filling pressures of all chambers increase.
- Findings offer insights into ventricular function in conditions like acute heart failure.
Abstract:
By using excised postmortem hearts obtained from 15 mongrel dogs with the pericardium intact, we investigated mechanical interactions between the four heart chambers from the standpoint of ventricular pressure-volume relationships. The interactions investigated were those between (1) the atrium and the ventricle, (2) the right ventricle and left ventricles, (3) the atrium and one ventricle vs. the other ventricle, and finally (4) the left and right atrium and the right ventricle vs. the left ventricle. For these purposes, we inserted compliant balloons into the four heart chambers without injuring the pericardium, i.e., we incised the base of the atria which was not covered with the pericardium. We obtained the right and/or left ventricular pressure-volume relationships under a constant pressure in three other heart chambers by changing the height of the reservoir connected to each balloon. As a result, both ventricular pressure-volume relationships were hardly affected by an increase in the atrial pressure ranging from 5 to 30 cm H2O with the pericardium removed, although the ventricle became less compliant due to an increase of the same magnitude of the opposite ventricular pressure. On the other hand, the effect of an increase in atrial pressure was distinct with the pericardium intact. Also, all mechanical interactions were enhanced dramatically with the intact pericardium. Thus, the pericardium plays an important role in these mechanical interactions, especially when the filling pressures of all heart chambers increase simultaneously. Clinically, these findings may be important to understanding ventricular functions as related to various heart disease-especially acute heart failure.