This study aims to explore the structural and functional characteristics of the pulmonary vasculature in adult Fontan patients.

Objectives:

• Determine the effect of pulmonary vasodilatation on indexed cardiac output during simulated exercise.
• Characterization of structural properties of small pulmonary arteries.

Rationale:

The Fontan circulation is a palliation for patients with a functionally univentricular heart. The Fontan circulation is characterized by impaired exercise capacity and gradual attrition over time. To date treatment options are extremely limited. It has been proposed that pulmonary vascular resistance (PVR) is the controlling and limiting factor of cardiac output in the Fontan circulation. Remodeling of the pulmonary vasculature and increasing PVR are possible key factors in the long term failure of the Fontan circulation. Optical Coherence Tomography (OCT) is an intravascular imaging modality used for structural characterization of blood vessels. Nitric oxide is a pulmonary vasodilator used in pulmonary vascular response tests, aimed at lowering PVR which may improve cardiac output in the Fontan circulation. These two diagnostic procedures are tools to study the structural and functional characteristics of the pulmonary vasculature in the Fontan circulation. The results of this study could identify the pulmonary circulation as a future treatment target in Fontan patients and may provide clues for new therapeutic treatment strategies to improve the long term outcome of these patients.

Study procedure:

The study protocol will be performed during a clinically indicated cardiac catheterization. In the context of this study additional measurements will be performed which will include a pulmonary vascular response test, trans-thoracic echocardiography and pulmonary artery OCT measurements.

Inclusion criteria:

Fontan group

• written informed consent
• Clinical indication for cardiac catheterization

Control group

• written informed consent
• Clinical indication for right heart catheterization
• Absence of pulmonary vascular disease
• Normal pulmonary vascular hemodynamic profile

Exclusion criteria:

Fontan group

• Standard exclusion criteria for cardiac catheterization
• Obstruction in Fontan conduit
• Inability to measure a reliable cardiac index and PVR (rhythm instability, hemodynamic or anatomic reasons)

Control Group

- No specific exclusion criteria apart from the standard exclusion criteria for right heart catheterization.

All adult patients (≥18 years), who attend the University Medical Center Groningen for follow-up after a Fontan completion.

Additionally 5 adult patients (≥18 years) without a Fontan circulation and without a univentricular heart-like diagnosis but with a clinical indication for right heart catheterization and normal values at right heart catheterization measurements will be included to serve as controls for the pulmonary artery OCT analysis.