1Universitätsklinikum Schleswig-Holstein Klinik für angeborene Herzfehler und Kinderkardiologie Kiel, Deutschland; 2Universitätsklinikum Schleswig-Holstein Innere Medizin III mit den Schwerpunkten Kardiologie, Angiologie und internistische Intensivmedizin Kiel, Deutschland
Background
Hypoplastic left heart syndrome (HLHS) is a complex univentricular congenital heart defect with underdevelopment of all left heart structures. Long-term management of HLHS typically involves the series of three surgical steps to establish a Fontan circulation starting with the Norwood operation during the early neonatal period. Due to scarring from extensive atrial surgery and hemodynamic stress, atrial arrhythmias are common.
Clinical Case
We report on a 17-year-old boy with HLHS who underwent surgical palliation establishing a Fontan circulation. The Fontan tunnel was built as an intra-atrial lateral tunnel (IALT) using Gore-Tex with a 4 mm fenestration, marked with four metal clips, connecting the IALT with the common atrium. In this case, stenosis of the neo-aortic valve resulted in the need for valve repair, followed by valve replacement initially with a homograft and finally with a mechanical valve prosthesis.
Since 2016, the patient experienced multiple episodes of atrial tachycardia (AT). Despite medical treatment with bisoprolol and flecainide, the arrhythmia burden increased, and exercise tolerance declined so that an electrophysiological study (EP) aiming to ablate arrhythmia was felt indicated.
The EP study was conducted during ongoing (AT) with cycle length 260ms. A 10-pole diagnostic catheter (DECANAV®, Biosense Webster) was positioned as a reference on the lateral wall of the IALT. Passage through the fenestration with a long steerable sheath (Agilis™ NxT, Abbott) could only be achieved after dilation with a 5 x 20 mm Cutting Balloon (Peripheral Cutting Balloon™, Boston Scientific) (Fig.1). The activation map (Carto® 3 System, Biosense Webster) revealed a counterclockwise cavotricuspidal isthmus (CTI)-dependent re-entry around the tricuspid valve (TV). In our case, not only the right atrium (as typical in atrial flutter), but the whole common atrium was included into the reentry circuit. (Fig. 2A & 2B). Linear ablation was successfully performed, CTI- block could be confirmed. Programmed pacing resulted in induction of another AT with an unstable CL between 400-450ms. Re-mapping revealed a focal mechanism originating in the upper third of the anterolateral suture site of the Gore-Tex patch into the lateral atrial wall (Fig. 3A & 3B). Ablation was performed from the tunnel side and led to the termination of the tachycardia. Hours after the ablation the focal AT (FAT) recurred, bisoprolol and flecainide were gradually reintroduced, and the tachycardia terminated. The post-interventional echocardiography showed an unchanged tunnel fenestration, the oxygen saturation remained unchanged. In the follow-up post-ablation, the patient reported improved well-being and almost no palpitations. Long-term ECG monitoring showed occasional FAT at night, prompting us to continue the medication therapy.
Conclusion
In Fontan patients, atrial tachycardia can have various mechanisms. If needed, a Cutting Balloon can be used to effectively enlarge the fenestration in the IALT to allow passage of a long steerable sheath.