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Published on: November 20, 2016
THE PHYSIOLOGICAL RESPONSE OF THE CIRCULATORY SYSTEM TO EXPERIMENTAL ALTERATIONS : II. THE EFFECT OF VARIATIONS IN
1Laboratory of Surgical Research, Lakeside Hospital and Western Reserve University, Cleveland.
Insights
The pericardium limits acute heart dilation by restricting expansion. While it adapts to chronic pressure, exceeding vena cava pressure is fatal; however, pericardiectomy had no lasting negative effects.
Area of Science:
- Cardiovascular Physiology
- Cardiac Anatomy
Background:
- The pericardium's role in cardiac function is debated.
- Existing research suggests the pericardium may limit acute heart dilation.
Purpose of the Study:
- To investigate the pericardium's constrictive effects on acute cardiac dilatation.
- To explore the pericardium's adaptive capacity under prolonged tension.
- To assess the consequences of exceeding critical intrapericardial pressure.
Main Methods:
- Experimental manipulation of cardiac volume and pericardial tension.
- Observation of hemodynamic changes during acute dilatation.
- Evaluation of pericardial adaptation to sustained pressure (effusion model).
- Assessment of outcomes following pericardiectomy.
Main Results:
- The pericardium exerts a limiting action on acute heart dilatation.
- Prolonged tension leads to pericardial enlargement, as seen in effusion.
- Intrapericardial pressure equaling vena cava pressure results in fatal cessation of cardiac inflow.
- Pericardiectomy in dogs showed no significant long-term adverse effects on health, exercise response, or heart size.
Conclusions:
- The pericardium functions as a critical restraint against acute cardiac dilatation.
- While adaptable to chronic stress, exceeding venous pressure is incompatible with life.
- Surgical removal of the pericardium does not appear to compromise overall cardiovascular health or function in the long term.
Abstract:
The pericardium presents a limiting or constricting action to acute dilatation of the heart. The diastolic pressure tends to approach the systolic pressure in a circulatory system distended with blood. The limiting action of the pericardium may be responsible for the small differences in the size of the heart noted by Meek and Eyster in their studies on the effect of plethora. The views concerning the function of the pericardium are divergent. That it may restrict the heart in cases of acute dilatation is shown in the above experiments. If the tension upon the pericardium be exerted over a prolonged period of time, as occurs in cases of pericardial effusion, the pericardium readily enlarges. If, however, the intrapericardial pressure should at any time equal the pressure in the venae cavae, blood would no longer enter the heart and the condition would become fatal. In recovery experiments, pericardiectomy was followed by no demonstrable effect upon the general health of the dog, upon the response to exercise, or upon the size of the heart (6).
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