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Ventricular energetics after the Fontan operation: contractility-afterload mismatch
Gábor Szabó1, Volker Buhmann, Andy Graf
1Department of Cardiac Surgery, University of Heidelberg, Germany. dzsi@hotmail.com
The Journal of Thoracic and Cardiovascular Surgery
|May 29, 2003
Summary
Fontan circulation impairs cardiac function by creating a mismatch between contractility and afterload, leading to reduced mechanical efficiency and limited cardiac reserve. This study analyzed ventricular-vascular coupling to understand these effects.
Area of Science:
- Cardiovascular Physiology
- Pediatric Cardiology
- Surgical Outcomes
Background:
- Fontan-type operations create a single-ventricle circulatory system, essential for patients with complex congenital heart defects.
- The hemodynamic effectiveness of this single-ventricle physiology is critical for patient outcomes, influencing both resting and exercise capacity.
Purpose of the Study:
- To investigate cardiac performance following Fontan operations using a ventricular-vascular coupling framework.
- To analyze the impact of Fontan circulation on myocardial contractility and arterial load.
- To quantify changes in mechanical efficiency and energy transfer within the Fontan circulatory system.
Main Methods:
- Utilized a canine model (n=12) with established Fontan circulation via cavopulmonary anastomosis.
- Measured left ventricular hemodynamics using a pressure-volume-conductance catheter system.
- Quantified ventricular contractility (end-systolic pressure-volume relationship slope) and arterial load (end-systolic pressure/stroke volume ratio).
- Calculated ventriculoarterial coupling ratio, stroke work, total mechanical energy, and mechanical efficiency.
Main Results:
- Fontan circulation significantly decreased ventricular contractility (slope of end-systolic pressure-volume relationship) and increased arterial load.
- The ventriculoarterial coupling ratio significantly increased, indicating a mismatch between the ventricle and arterial system.
- Stroke work and mechanical efficiency were significantly reduced in the Fontan circulation model.
Conclusions:
- Fontan circulation results in a contractility-afterload mismatch, partly due to increased impedance and myocardial contractility deterioration.
- The observed increase in ventriculoarterial coupling and reduced mechanical efficiency suggest limited cardiac functional reserve post-Fontan operation.
- These findings highlight the importance of understanding ventricular-vascular interactions for optimizing outcomes in Fontan patients.