Maximal hemodynamic response after the Fontan procedure: Doppler evaluation during the treadmill test

Area of Science:

• Pediatric Cardiology
• Cardiovascular Physiology

Background:

• The Fontan procedure is a palliative surgery for complex congenital heart disease.
• Assessing exercise capacity is crucial for monitoring Fontan-associated physiology.

Purpose of the Study:

• To evaluate the hemodynamic response to maximal exercise in young patients post-Fontan procedure.
• To compare exercise performance and cardiac function between Fontan survivors and healthy children.

Main Methods:

• 16 young patients who underwent the Fontan procedure performed a maximal treadmill test (Bruce protocol).
• Continuous-wave Doppler echocardiography measured peak aortic blood flow velocity, stroke index, and cardiac index at rest and during exercise.
• Hemodynamic data were compared to 18 age-matched healthy children.

Main Results:

• Fontan patients had a 37% shorter endurance time than controls.
• Stroke index increase was blunted in Fontan patients during submaximal exercise and decreased at maximal exercise.
• Cardiac index response was comparable initially but failed to ascend in Fontan patients at maximal exercise.
• Hemodynamic values, including cardiac index increase (79% vs. 170%), were significantly lower in the Fontan group at maximal exercise.

Conclusions:

• Fontan survivors exhibit subnormal stroke volume response during exercise.
• Impaired cardiac index response and reduced endurance highlight functional limitations post-Fontan procedure.
• These hemodynamic findings are critical for understanding exercise intolerance in Fontan patients.