Atrial fibrillation ablation in a single atrium with inferior vena cava interruption

Abstract Common atrium (CA), also called three‐chambered heart, is one of the rare congenital anomalies, defined by a complete absence of the atrial septum, eventually associated with malformation of the atrioventricular (AV) valves. We report the case of a 57‐year‐old woman with CA complicated with Eisenmenger syndrome and inferior vena cava interruption, who suffered from symptomatic persistent atrial fibrillation (AF). She underwent an initial successful pulmonary vein isolation procedure. A repeat procedure for perivalvular atrial flutter was complicated with inadvertent complete AV block, due to unusual AV node location in this challenging anatomy.


| C A S E PR E S E NTATI O N
Common atrium (CA), also called three-chambered heart or cor triloculare biventriculare, is one of the rare congenital anomalies, (Garg et al., 2020) defined by a complete absence of the atrial septum, eventually associated with malformation of the atrioventricular (AV) valves. We report the case of a 57-year-old woman with CA complicated with Eisenmenger syndrome, who suffered from symptomatic persistent atrial fibrillation (AF). The patient did not have any muscular, skeletal, ophthalmologic, or vascular abnormalities to signify that her abnormalities were part of any congenital syndrome.
Visceroatrial, atrioventricular, and ventriculoarterial concordance were noted. Nevertheless, she also presented inferior vena cava (IVC) interruption. During her last clinical evaluation, a mild holosystolic murmur was heard at all auscultation points, gaining intensity at the apex and mesocardiac area. On physical examination, while S1 was normal, a widely split S2 was heard. There was no pretibial edema, and the lungs were clear. Oxygen saturation measured with finger pulse oximetry was 92%.
Her last echocardiography evaluation showed in apical view the absence of interatrial septum (Figure 1). CA surface was 50 cm 2 . Left ventricular ejection fraction was 60%. In addition to right ventricular dilatation, moderate tricuspid regurgitation was seen, along with severe pulmonary hypertension. Tricuspid annular plane systolic excursion 17 mm. Mitral and tricuspid valve attachments to the interventricular septum were on the same anatomic plane, and there was a small cleft present in the mitral valve, with mild regurgitation. Paradox movement of the interventricular septum was observed but without any interventricular communication.
Cardiac catheterization revealed systolic pulmonary arterial pressure around 102 mmHg. Right ventricular pressure was 116/0 mmHg denoting severe pulmonary hypertension, RV end-diastolic pressure at 21 mmHg, mean CA pressure as 13 mmHg, and left ventricular end-diastolic pressure as 12 mmHg.
The patient was treated with furosemide, spironolactone, with anticoagulation by rivaroxaban. Rate control was achieved with a low dose of acebutalol. Because CA was diagnosed at a late stage, Received: 3 December 2022 | Revised: 9 January 2023 | Accepted: 28 February 2023 DOI: 10.1111/anec.13057

Atrial fibrillation ablation in a single atrium with inferior vena cava interruption
complicated with severe pulmonary hypertension despite combined therapy with bosentan and tadalafil (the later added since 2017), the patient was managed conservatively with no intervention to correct the congenital anomalies.
In March 2021, the patient presented a first episode of highly symptomatic persistent AF, with fast ventricular response (mean 150 beats per minute, with left anterior fascicular block, QRS width 110 ms) that benefited from successful electrical cardioversion (200 J delivered). Nevertheless, because of recurrent palpitations despite amiodarone after electrical cardioversion, a percutaneous AF ablation was decided 1 month later.

| Atrial fibrillation ablation procedure
Before planning the procedure, the patient underwent a computed tomography aiming for three-dimensional reconstruction.
The right superior vena cava was present and joined preferentially the right side of the CA. There was a connection of a supra-hepatic vein at the inferior part of the CA, instead of the IVC. There was a normal drainage of pulmonary veins to the left side of the CA. contact force (30% of time > 3 g). RF was delivered (SmartAblate®, Biosense Webster Inc.) in a power-controlled mode with 35 to 45 W. Target values of ablation index were 450 to 550 (≥450) at the anterior wall, ≥400 on the roof and 300 to 400 (≥300) at the posterior wall. At the vicinity of the esophagus, RF was delivered until an ablation index target of 300. To achieve PVI, an inter-vein line was performed within the right circle, associated with a posterior line as well (Figure 2). Complete PVI was achieved at the end of the procedure. The day after the procedure, a mild pericardial effusion was noticed, needing symptomatic treatment with colchicine. On day 3, the patient developed "typical" clockwise atrial flutter with prolonged QTc interval (600 ms), leading to amiodarone interruption, then switched by acebutalol. Because of persistent symptomatic atrial flutter (cycle length 270 ms) in the blanking period, another ablation procedure was performed 1 month later ( Figure 2b). Activation mapping showed a peri-valvular circuit that was interrupted by creating a line between the interrupted IVC and the valve. During RF delivery, an inadvertent and complete AV block occurred with junctional escape at 50 beats per minute, without any His potential recorded during high-density mapping.
A dual-chamber pacemaker had to be implanted in the right pectoral region. The hospitalization was uneventful, and the patient was discharged after 2 days. After 20 months of follow-up, the patient was free from any atrial arrhythmia recurrence without antiarrhythmic drug therapy.

| DISCUSS ION
To the best of our knowledge, this is the first description of PVI in a patient with CA. Since its first description by Young & Robinson (1907/1908 term SA should be reserved to the following condition: (a) complete absence of interatrial septum, (b) absence of malformation of the AV valves, and (c) absence of interventricular communication. Only three previous case reports described the presence of documented AF in patients with CA. The eldest patient to date with CA, was a 60-year-old female patient with permanent AF (Rawala et al., 2019). Kim et al. (2016) presented a 48-year-old male patient who was admitted for intermittent palpitations starting 1 week ago. AF was the initial manifestation leading to unmask CA. AF was managed with amiodarone and warfarin until surgery in this patient. In the case report from Altıntaş et al. (2017), AF was also the first manifestation of SA in a 43-year-old female patient, anticoagulated with dabigatran 150 mg bid. Actually, structural abnormalities (as well as genetic) should be investigated when discovering AF in young patients (Stoyanov et al., 2014).
Our case emphasizes the difficulties of performing an ablation procedure in complex anatomies. The first description of cavotricuspid isthmus ablation via a superior approach was reported by Varma et al. (2004). Later remote magnetic navigation was used to access transhepatic route via the femoral vein (Latcu et al., 2012).
Even if associated with a high success in experienced centers, electrophysiological procedures are still challenging in the presence of IVC interruption (Al-Sinan et al., 2022;Pons et al., 2012). In this recent study, IVC interruption was integrated with congenital heart disease in 43% of the cases. Liang et al. (2020)  Conduction disturbances are not rare in patients with endocardial cushion defects (Mehta et al., 1982). Hasanin & Kinsara (2008) reported the case of a 24-year-old soldier with syncopal attacks attributed to paroxysmal complete AV block in the setting of SA with persistent LSVC. Catheter ablation may be difficult in patients with congenital heart disease, because of potentially deviant and often unpredictable sites of the specific conduction system (Waldmann et al., 2022). Khairy et al. (2007) reported a case of inverted AV nodal input in a 25-year-old patient with surgically repaired partial AV canal defect.

| CON CLUS ION
A rare case of atrial fibrillation ablation is presented in a 57-year-old patient with common atrium and inferior vena cava interruption.
Special considerations should be taken when performing an ablation procedure in this challenging anatomy, especially concerning the likelihood of atypical location of the atrioventricular node.

AUTH O R CO NTR I B UTI O N S
S.-S.B.: writing, review and editing; F.S. and D.S.: investigation and data collecting; P.M.: validation; E.F.: supervision.

CO N FLI C T O F I NTE R E S T S TATE M E NT
Nothing to disclose.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author upon reasonable request.

E TH I C S S TATEM ENT
The patient provided her consent for the study.