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Arrhythmia in Fontan Circulation — EECC MCQ

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HardCongenital Heart Disease (Adult)Arrhythmia in Fontan CirculationEECC

A 50-year-old man with a Fontan circulation develops atrial flutter with rapid ventricular response. He is haemodynamically unstable. What is the key difference in managing atrial arrhythmias in Fontan patients compared with structurally normal hearts?

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Correct answer: E — Atrial arrhythmias in Fontan are poorly tolerated (loss of AV synchrony severely reduces cardiac output in a circulation dependent on passive pulmonary blood flow); urgent cardioversion and aggressive rhythm control are essential

The Fontan circulation is uniquely dependent on: (1) low PVR (to allow passive pulmonary blood flow); (2) adequate venous return; (3) AV synchrony (atrial contraction contributes ~30% of cardiac output vs ~15% in normal hearts). Atrial arrhythmias (common in Fontan due to atrial scarring, dilatation, and haemodynamic abnormalities) are poorly tolerated — loss of atrial kick causes significant CO reduction and symptoms. The 2020 ESC ACHD Guidelines recommend: urgent cardioversion for haemodynamic instability, aggressive rhythm control (amiodarone is often used), catheter ablation for recurrent arrhythmias (though technically challenging due to complex anatomy), and anticoagulation for all Fontan patients with atrial arrhythmias regardless of stroke risk scores.

Reference: ESC (2020): ACHD Guidelines