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Chronic pressure overload hypertrophy decreases direct ventricular interaction
Insights
In hypertrophied hearts, direct ventricular interaction is less significant than series interaction for determining left ventricular size. This finding impacts comparisons between normal and enlarged hearts.
Area of Science:
- Cardiovascular Physiology
- Cardiac Mechanics
- Heart Failure Research
Background:
- Ventricular interaction, both direct (septal) and series (pulmonary circulation), influences cardiac function.
- Concentric left ventricular hypertrophy alters heart structure and mechanics.
- Understanding these interactions is crucial for interpreting pressure-volume relationships in disease states.
Purpose of the Study:
- To investigate the relative importance of direct and series ventricular interaction in concentric left ventricular hypertrophy.
- To analyze how hypertrophy affects the contribution of the interventricular septum and pulmonary circulation to ventricular size.
- To assess the impact of pericardial removal on these interactions.
Main Methods:
- Statistical modeling of transient responses in ventricular pressures and dimensions.
- Occlusion of vena cava and pulmonary artery in five open-chest anesthetized dogs.
- Induction of moderate concentric left ventricular hypertrophy via renovascular hypertension.
Main Results:
- At end diastole, direct interaction was one-tenth as important as series interaction in determining left ventricular size (with pericardium).
- At end systole, direct interaction was one-fifth as important as the end-systolic pressure-volume relationship.
- Pericardium removal reduced the significance of direct ventricular interaction.
Conclusions:
- Direct ventricular interaction plays a diminished role in hypertrophied hearts compared to normal hearts, likely due to septal thickening.
- The reduced distensibility of the thickened septum limits direct interaction's influence.
- Altered relative importance of ventricular interaction complicates pressure-volume relationship comparisons between normal and hypertrophied hearts.
Abstract:
We studied the relative roles of direct (via the interventricular septum) and series (via the pulmonary circulation) ventricular interaction in hearts with concentric left ventricular hypertrophy by using statistical models to analyze the transient responses in right and left ventricular pressures and dimensions to occlusions of the venae cava and pulmonary artery in five open-chest anesthetized dogs. The left ventricles of these dogs had moderate concentric hypertrophy (31% increase in mass) induced by 3 mo of renovascular hypertension [peak left ventricular pressure = 160 +/- 13 (SD) mmHg]. At end diastole we found that direct interaction was only about one-tenth as important as series interaction in determining left ventricular size with the pericardium around the heart. At end systole we found that direct interaction was about one-fifth as important as the end-systolic pressure-volume relationship in determining left ventricular size. Removing the pericardium decreased the importance of direct interaction. Direct interaction is less important in these hearts than in normal hearts, probably because the septum is thicker and, hence, less distensible. This change in the relative importance of direct ventricular interaction with hypertrophy complicates comparison of pressure-volume relationships between normal and hypertrophied hearts.