Abstract
Atrial flutter (AFL) is uncommon in children without underlying heart disease. This report details the case of a 7-year-old boy with AFL detected during school electrocardiogram (ECG) screening. He had no prior arrhythmias, congenital heart disease, or cardiomyopathy. Initial evaluations showed AFL with right bundle branch block but no structural heart abnormalities. Radiofrequency catheter ablation (RFCA) was performed, initially resolving the AFL but resulting in a 13-s sinus arrest requiring atrial pacing. Post-RFCA, the patient experienced a sinus arrest lasting up to 7 s, leading to a diagnosis of sick sinus syndrome (SSS). A second RFCA was needed due to AFL recurrence, and post-ablation ECGs revealed saddleback-type ST-segment elevation and Brugada-type patterns, raising suspicion of Brugada syndrome (BrS). Genetic testing identified a loss-of-function (LOF) SCN5A variant (c.2678G > A p.R893H) in the patient, his mother, and his sister. This case underscores that AFL in children without structural heart disease, especially when associated with SSS, may be linked to LOF SCN5A variants, which are also associated with BrS.
Learning objective
Atrial flutter in children without structural heart disease can be linked to genetic factors with Brugada syndrome (BrS). This case highlights the importance of thorough diagnostic evaluation, including family history and genetic testing, when rare arrhythmias are present. Early detection of BrS through detailed electrocardiographic findings and family screening can help identify at-risk individuals and guide appropriate management to prevent serious arrhythmias and sudden cardiac death.
Introduction
Atrial flutter (AFL) is a common arrhythmia in adults but is rarely experienced in children, except in the neonatal period [ ]. Furthermore, it is uncommon for AFL to occur independently without a background of congenital heart disease or cardiomyopathy [ ]. Notably, pathogenic SCN5A variants are often present in such cases, sometimes associated with Brugada syndrome (BrS) or sick sinus syndrome (SSS), which can have a fatal outcome [ ]. Here, we describe a case of BrS presenting with SSS and electrocardiographic changes after radiofrequency catheter ablation (RFCA) for common counterclockwise AFL.
Case report
A 7-year-old boy presented to the hospital with AFL found during a school electrocardiography (ECG) screening. He had no history of syncope, convulsions, or cardiac events. He underwent surgery for a buried penis at the age of 5 years, during which ECG showed AFL, but no significant perioperative issues were noted. AFL was not recognized at that time. There was a family history of sudden death in his maternal grandfather at age 30 years. Moreover, the patient had no history of arrhythmia except for AFL, congenital heart disease, or cardiomyopathy.
Physical examination revealed a height of 120.6 cm and a weight of 24.0 kg. An irregular heart sound was noted, but there were no gallops or murmurs. No abnormalities were found in respiratory, abdominal, or neurological examinations. Similarly, blood tests were unremarkable, with hemoglobin at 13.4 g/dL, aspartate aminotransferase at 28 IU/L, alanine aminotransferase at 12 IU/L, creatine kinase at 103 IU/L, lactate dehydrogenase at 259 IU/L, brain natriuretic peptide at 14.1 pg/mL, thyroid stimulating hormone at 1.52 μIU/mL, free triiodothyronine (T3) at 4.46 pg/mL, and free thyroxine (T4) at 1.74 ng/mL. Chest radiography revealed a cardio-thoracic ratio of 45 %. The 12‑lead ECG showed AFL with a 3:1–5:1 atrioventricular conduction and a right bundle branch block ( Fig. 1 a ). Echocardiography revealed no structural abnormalities and good cardiac function with a left ventricular ejection fraction of 65 %. No myocardial changes suggestive of cardiomyopathy were observed. Holter ECG demonstrated a persistent AFL with 2:1–5:1 conduction and no sinus rhythm. Warfarin was initiated for anticoagulation due to persistent AFL without confirmed sinus rhythm. Contrast enhanced computed tomography showed no intracardiac thrombus.
Three months after diagnosis of AFL, RFCA was performed for common counterclockwise AFL under general anesthesia, induced by midazolam bolus injection and maintained by continuous infusion of dexmedetomidine hydrochloride. An 8.5F sheath, 7.5F sheath, and 5F sheath were inserted into the right and left femoral veins respectively. Next, 5F electrode catheters (EPstar Snake; Japan Lifeline, Tokyo, Japan) were placed in the right atrium along the tricuspid valve to the coronary sinus (CS) and from the septal to the lateral wall (POLALYON™; Boston Scientific Japan, Tokyo, Japan). AFL was terminated by atrial stimulation during the insertion of the Halo electrode catheter, which resulted in a 13-s sinus arrest necessitating atrial pacing ( Fig. 1 b). Ultrahigh-density three-dimensional mapping using the ORION™ high-density catheter and the RHYTHMIA™ Mapping System (Boston Scientific Japan) was then performed. Linear ablation was executed along the inferior vena cava-tricuspid valve interatrial line during CS pacing. Temporary pacing was used until the next day.
After RFCA, his heart rate was unstable, alternating between sinus and junctional rhythms at 30–40 bpm. He was managed in the intensive care unit with continuous isoproterenol administration and an external pacemaker. AFL recurred on post-RFCA day 2 and persisted until cardioversion was performed, and the patient was restored to sinus rhythm. A Holter ECG after the first RFCA showed sinus arrest lasting up to 7 s. Therefore, he was diagnosed with SSS.
One month after his discharge, common counterclockwise AFL recurred, necessitating a second RFCA. Ultrahigh-density three-dimensional mapping using the ORION™ high-density catheter and the RHYTHMIA™ Mapping System revealed a gap near the tricuspid valve. Radiofrequency application at this site terminated the AFL. After the second RFCA, the patient experienced sinus arrest lasting up to 3.4 s. The voltage map of the right atrium revealed an abnormal low voltage area around the sinus node during both AFL and sinus rhythm ( Fig. 2 a, b). The electrophysiological study did not evaluate sinus node function. His heart rate increased with activity, and he remained asymptomatic, allowing for follow-up without medication. Warfarin was discontinued two months after the second catheter ablation, as no AFL recurrence was observed.
