The Fontan circulation: who controls cardiac output?

Area of Science:

• Cardiology
• Pediatric Cardiology
• Physiology

Background:

• Cardiac output regulation in Fontan circuits deviates from normal physiology.
• The classical model of cardiac output is insufficient for Fontan patients due to limited preload availability.

Purpose of the Study:

• To critically analyze factors influencing cardiac output in Fontan patients.
• To highlight the significance of pulmonary vascular resistance (PVR) in Fontan physiology.
• To present a conceptual model for cardiac output determinants in Fontan circulation.

Main Methods:

• Literature review focusing on cardiac output control mechanisms.
• Critical analysis of contractility, heart rate, and afterload in Fontan patients.
• Development of a conceptual model based on existing evidence.

Main Results:

• Contractility, heart rate, and afterload play distinct roles in Fontan physiology.
• Pulmonary vascular resistance (PVR) is a key determinant of preload and cardiac output.
• The Fontan circuit presents unique challenges to maintaining adequate cardiac output.

Conclusions:

• Understanding Fontan physiology requires moving beyond classical cardiac output models.
• Pulmonary vascular resistance is a critical therapeutic target for optimizing cardiac output in Fontan survivors.
• A new conceptual model clarifies the determinants of cardiac output in this complex patient population.