Study of Effects of Sildenafil on Patients With Fontan Heart Circulation

Response to Sildenafil in Patients With Fontan Physiology, A Pressure-volume Loop Analysis

The study will investigate the cardiovascular effects of sildenafil on patients with Fontan circulation. Recent studies suggest that sildenafil may improve exercise in patients with Fontan circulation. However, why this occurs is not known. The study will used specialized catheters to measure pressure and volume. The measure of pressure and volume leads to more detailed analysis of heart function. Patients will receive either sugar pill or sildenafil prior to catheterization. It is believed that sildenafil will improve relaxation and contraction of the heart.

Modifications to surgical procedures and medical treatment have led to a rapidly declining mortality rates in patients with single-ventricle heart disease (SV). However, SV patients still suffer from lower quality of life, decreased exercise capacity, worse neurodevelopmental outcomes and many other morbidities. While patients with SV circulation only make a small portion of all congenital heart diseases, 2-4 %, they require a great deal of resource utilization.

Standard medical treatments for adult heart failure have not had the same success in the SV population. Phosphodiesterase 5 (PDE5) inhibitors have recently become a frequently used medication class in patients with SV heart disease to treat pulmonary hypertension, heart failure, as well as "Fontan" failure (i.e., plastic bronchitis and protein-losing enteropathy). While there have been findings of improved measures of exercise capacity and some reports of improved symptoms of heart failure, the physiologic mechanisms behind these findings are not completely understood. There have been reports, indicating that the phosphodiesterase five inhibitors improve ventricular function in biventricular circulation patients and animal models. The aim of our study was to investigate the effect of acute PDE5 inhibition on ventricular function in SV patients after the final palliative surgery, the Fontan procedure.

Inclusion Criteria:

• Presence of a congenital heart defect that leads to single ventricle physiology
• Previously performed Fontan surgery

Exclusion Criteria:

• The use of phosphodiesterase type 5 (PDE5) inhibitors at the time of catheterization of within 1 month of catheterization

  • Unstable arrhythmia at the time of catheterization
  • History of unstable arrhythmia within 2 months of catheterization
  • Venous, arterial or cardiac malformation that precludes the proper placement of a microconductance catheter
  • Allergy to sildenafil or previous significant adverse reaction to sildenafil (e.g. hypotension)