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Ventriculoarterial coupling in normal and failing heart in humans
H Asanoi1, S Sasayama, T Kameyama
1Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Japan.
Insights
Ventriculoarterial coupling optimizes heart efficiency. In healthy individuals, it maximizes work efficiency, while in moderate cardiac dysfunction, it prioritizes stroke work over efficiency, impacting cardiac performance.
Area of Science:
- Cardiovascular Physiology
- Cardiac Mechanics
- Hemodynamics
Background:
- Understanding ventriculoarterial coupling is crucial for assessing cardiac function.
- The relationship between ventricular and arterial properties influences overall cardiovascular efficiency.
- Cardiac dysfunction alters the balance between cardiac output and arterial load.
Purpose of the Study:
- To investigate the coupling between the left ventricle and the arterial system in healthy subjects and cardiac patients.
- To determine how ventricular elastance and effective arterial elastance change with varying ejection fractions.
- To analyze the impact of ventriculoarterial coupling on ventricular work efficiency and stroke work.
Main Methods:
- Measured left ventricular end-systolic pressure-volume relation (ventricular elastance) and arterial end-systolic pressure-stroke volume relation (effective arterial elastance).
- Assessed left ventricular stroke work, end-systolic potential energy, and ventricular work efficiency.
- Compared these parameters across three groups based on ejection fraction: normal (≥60%), moderate dysfunction (40-59%), and severe dysfunction (<40%).
Main Results:
- In normal subjects (Group A), ventricular elastance was nearly twice arterial elastance, optimizing mechanical efficiency.
- In moderate dysfunction (Group B), ventricular elastance approximated arterial elastance, maximizing stroke work at reduced efficiency.
- In severe dysfunction (Group C), ventricular elastance was less than half of arterial elastance, leading to increased potential energy and decreased work efficiency.
Conclusions:
- Normal ventriculoarterial coupling prioritizes left ventricular work efficiency.
- Moderate cardiac dysfunction shifts coupling to maximize stroke work, compromising efficiency.
- Severe cardiac dysfunction results in suboptimal stroke work and work efficiency due to mismatched ventriculoarterial properties.
Abstract:
To investigate coupling between the heart and arterial system in normal subjects and cardiac patients, we determined both the slope of the left ventricular end-systolic pressure-volume relation (ventricular elastance) and the slope of the arterial end-systolic pressure-stroke volume relation (effective arterial elastance) in three groups of subjects: group A, 12 subjects with ejection fraction of 60% or more; group B, seven patients with ejection fraction of 40-59%; and group C, nine patients with ejection fraction of less than 40%. We also determined the left ventricular stroke work, end-systolic potential energy, and the ventricular work efficiency defined as stroke work per pressure-volume area (stroke work + potential energy). In group A, ventricular elastance was nearly twice as large as arterial elastance. This is a condition for a maximal mechanical efficiency. In group B, ventricular elastance was almost equal to arterial elastance. This is a condition for maximal stroke work from a given end-diastolic volume. In group C, ventricular elastance was less than one half of arterial elastance, which resulted in increased potential energy and decreased work efficiency. Thus, the present study suggests that ventriculoarterial coupling is normally set toward higher left ventricular work efficiency, whereas in patients with moderate cardiac dysfunction, ventricular and arterial properties are so matched as to maximize stroke work at the expense of the work efficiency. Neither the stroke work nor the work efficiency is near maximum for patients with severe cardiac dysfunction.