Fontan Heart: Insight Into the Physiological Role of the Right Heart

Area of Science:

• Pediatric Cardiology
• Hemodynamics
• Congenital Heart Disease

Background:

• Right ventricular (RV) dysfunction is a clinical concern in Fontan physiology despite near-normal cardiac output (CO).
• Investigating the primary drivers of reduced CO in single-ventricle physiology is crucial.

Purpose of the Study:

• To test the hypotheses that increased pulmonary vascular resistance (PVR) is the dominant factor in reduced CO.
• To evaluate the efficacy of volume expansion in improving CO in the absence of a functional RV.

Main Methods:

• A previously developed MATLAB model was modified by removing the RV.
• Vascular volume, venous compliance (Cv), PVR, and left ventricular (LV) function were altered.
• CO and regional vascular pressures were the primary outcome measures.

Main Results:

• RV removal decreased CO by 25% and increased mean systemic filling pressure (MSFP).
• Increasing stressed volume moderately increased CO, with or without the RV.
• Increasing PVR significantly reduced CO in the absence of the RV.
• Enhanced LV function provided minimal improvement in CO.

Conclusions:

• Increased PVR is the dominant factor limiting CO in Fontan physiology.
• Volume expansion provides only moderate CO improvement.
• LV function has a limited role in improving CO in this model.