Sildenafil improves exercise hemodynamics in Fontan patients

Area of Science:

• Cardiovascular Physiology
• Pediatric Cardiology
• Pharmacology

Background:

• Patients with Fontan circulation exhibit reduced exercise capacity due to impaired cardiac output.
• The absence of a presystemic pump in Fontan physiology may limit pulmonary blood flow and ventricular filling.

Purpose of the Study:

• To evaluate exercise hemodynamics in Fontan patients.
• To assess the effect of sildenafil on exercise hemodynamics in this population.

Main Methods:

• Cardiac magnetic resonance imaging (CMR) was used to assess ventricular volumes at rest and during graded supine bicycle exercise in 10 Fontan patients.
• Hemodynamic parameters including cardiac index, stroke volume index, and resistance indices were measured before and after sildenafil administration.
• cGMP levels were also monitored.

Main Results:

• Exercise led to increased cardiac index but decreased stroke volume and end-diastolic volume in Fontan patients.
• Sildenafil significantly improved cardiac index and stroke volume index during exercise, particularly at high intensities.
• Sildenafil reduced systemic and total pulmonary resistance indices, with a notable decrease in pulmonary resistance during exercise.

Conclusions:

• Sildenafil enhances exercise cardiac index and stroke volume index in Fontan patients.
• The pulmonary vasculature is a significant physiological limitation in Fontan circulation, which can be attenuated by sildenafil.
• Further studies are warranted to determine the clinical significance of sildenafil in managing Fontan patients.