Noninvasive determination of exercise cardiac function following Fontan operation

Area of Science:

• Cardiology
• Pediatric Cardiology
• Physiology

Background:

• The Fontan procedure is a palliative surgery for complex congenital heart defects, creating a single ventricle physiology.
• Understanding the cardiovascular adaptations to exercise in these patients is crucial for managing their long-term health.
• Patients with single ventricle physiology lack a functioning right ventricle, impacting cardiac output dynamics.

Purpose of the Study:

• To define the mechanisms that increase cardiac output during exercise in patients with a single functioning ventricle.
• To investigate the hemodynamic responses to exercise in post-Fontan procedure patients.
• To compare exercise capacity and cardiac function in Fontan patients versus healthy children.

Main Methods:

• Radionuclide studies were conducted at rest and during upright bicycle exercise.
• 16 patients who underwent the Fontan procedure were studied.
• Data were compared to 10 age-matched healthy children.

Main Results:

• Patients following Fontan procedures demonstrated a significant increase in cardiac index from rest (5.2 L/min/m2) to exercise (9.4 L/min/m2).
• Exercise cardiac index in Fontan patients was comparable to that of normal children.
• Increased heart rate was a primary mechanism for augmenting cardiac output; however, mean systemic ventricular ejection fractions were lower than in controls.

Conclusions:

• Patients without a functioning right ventricle can achieve substantial cardiac output during exercise.
• Compensatory mechanisms, including increased heart rate, allow for adequate exercise performance despite altered ventricular function.
• These findings highlight the adaptability of the single ventricle system in response to physiological stress.