Exercise-Induced Systemic Venous Hypertension in the Fontan Circulation

Area of Science:

• Cardiology
• Physiology
• Pediatric Cardiology

Background:

• Late end-organ injury, including liver fibrosis and cirrhosis, is increasingly observed in patients with Fontan circulation.
• The precise mechanisms underlying these late-onset complications remain poorly understood.
• Exercise may precipitate systemic venous hypertension and inadequate cardiac output, contributing to end-organ damage.

Purpose of the Study:

• To investigate the dynamic exercise responses in systemic venous perfusion (SVP) and concurrent end-organ perfusion in Fontan patients.
• To test the hypothesis that exercise induces systemic venous hypertension and insufficient cardiac output in Fontan circulation.

Main Methods:

• Ten stable adult Fontan patients and nine healthy controls underwent incremental cycle ergometry.
• Systemic venous perfusion (SVP) was monitored in the right upper limb.
• Regional tissue oxygen saturation in the brain and kidney was measured using near-infrared spectroscopy.

Main Results:

• SVP increased significantly with workload in Fontan patients (15.97 + 0.073 mm Hg/watt), but not in controls.
• Fontan patients exhibited significantly lower and more rapidly decreasing renal and cerebral tissue oxygen saturations during exercise.
• Exercise was associated with systemic venous hypertension and reduced systemic oxygen delivery in Fontan patients.

Conclusions:

• High-intensity exercise in stable adult Fontan patients is linked to systemic venous hypertension.
• Reduced systemic oxygen delivery during exercise in Fontan patients may contribute to end-organ injury.
• These findings suggest a potential mechanism for late-onset organ damage in Fontan circulation.