Sudden Cardiac Arrest during Anesthesia in a 30-Month-Old Boy with Syndactyly: A Case of Genetically Proven Timothy Syndrome
A 30-month-old boy suddenly experienced cardiac arrest during anesthesia induction with sevoflurane and nitric oxide before undergoing plastic surgery for bilateral cutaneous syndactyly of the fingers (third, fourth, and fifth digits) on June 7, 2004 (). After 10 min of resuscitation, sinus rhythm was recovered, and an electrocardiogram (ECG) showed a prolonged QT interval (QTc, 0.58-0.60 sec). Before the operation, the patient had never undergone ECG. During the Holter study, T-wave alternans and functional 2:1 AV block due to QT prolongation was also observed, suggesting LQTS ().\nOn the patient's echocardiogram, intracardiac anomaly was absent, and ventricular function was normal. The preoperative biochemical analysis result was normal; in addition, the electrolyte level was normal. The patient had a round face, small upper jaw and teeth, and nearly bald head; he had fused fingers but normal toes, no history of seizure or syncope, and normal neurodevelopment. The patient was born via vaginal delivery without any complications. The patient's family, particularly his older sister, had no history of syncope, seizure, or sudden death. The QT intervals of the father, mother, and sister were not significantly prolonged, as determined by ECG. The epinephrine stress test result of his sister showed a paradoxical QT interval prolongation (QTc baseline 0.4 → peak 0.53 sec), but she was asymptomatic. Genetic tests were not administered to the patient's parents and sister. No other arrhythmic events were detected, and a β-blocker (propranolol) was administered 3 times a day (1 mg/kg/dose) to prevent further tachycardia and collapse event. After supportive care for hypoxic brain damage, the patient was discharged with propranolol (2 mg/kg/day), and his neurological function returned to its premorbid state after one month. Although there was persistent severe QTc prolongation with intermittent 2:1 functional AV block, the patient underwent repeated plastic surgery for syndactyly without any arrhythmic event (at the age 4 and 5 yr), with propranolol and mexiletine. Mexiletine was prescribed from the ages of 4-7 yr on the supposition that he might be LQTS type 3 due to very long QTc interval, late appearing high amplitude T wave, and repolarization-dependent atrioventricular block. It has been discontinued since the result of SCN5A genes mutation test came out negative informally. The short acting β-blocker, propranolol, was changed to long acting β-blocker, atenolol, at the age of 10 yr old.\nAt the age of 6 yr, one morning, the patient had a generalized tonic-clonic seizure that lasted for 10 min; his blood glucose level was 38 mg/dL, with no other symptoms. There were no specific findings on his electroencephalogram and magnetic resonance imaging scan, and no recurring seizure was reported. Moreover, the result of the gene study performed during this time was negative for KCNQ1 and KCNH2 mutations. At the age of 10 yr (2011), mutations were absent in the KCNE1, KCNE2, and SCN5A genes, but point mutation c.1216G > A in exon 9 in CACNA1C was confirmed (). However, the patient's family refused to undergo the recommended gene study.\nThe patient was administered a β-blocker (atenolol at 0.35 mg/kg/dose bid) for 8 yr. The QT prolongation on ECG (QTc, 0.65 sec) and T-wave alternans on Holter monitoring persisted, but syncope or cardiac arrest did not recur during the 8-yr follow-up period.