Heart block during the acute phase of Kawasaki disease

Sir, A 4-y-old male presented to the emergency room at The Hospital for Sick Children, Toronto, Canada, with a 6-d history of fever. He had nasal congestion, and cough. He looked unwell and mildly dehydrated. By day 2 of admission, the patient had developed all the criteria for Kawasaki disease (KD). He remained febrile, had a left cervical node 3 cm in diameter, peripheral extremity changes with swollen hands and feet, red lips and tongue, bilateral nonpurulent conjunctivitis, and a maculopapular rash on the trunk. The cardiovascular examination was normal. Serum laboratory results were all normal: white blood cells 10 /10/l, hemoglobin 123 g/l, platelets 410/l and ESR 6 mm/h. A nasopharyngeal swab was positive for influenza A by immunofluorescence. A chest X-ray revealed no cardiomegaly or pulmonary infiltrates. In view of the concurrent influenza A infection, aspirin was not prescribed because of the risk of development of Reye’s syndrome. Intravenous immunoglobulin (IVIG) was administered at a dose of 2 g/kg. During the IVIG infusion, the patient’s heart rate was noted to be 50 bpm. Prior to the infusion, the heart rate was consistently recorded as 120 to 140 bpm. The patient remained well perfused, normotensive, and had no murmur or gallop rhythm. An electrocardiogram (ECG) revealed a type 1 seconddegree heart block. There were no ST segment changes or Q waves. A repeat chest X-ray was normal. Repeat laboratory examination was unremarkable, including serum creatinine phosphokinase. Echocardiography revealed no coronary artery aneurysms or valvular disease. There was good biventricular function with a left ventricular ejection fraction of 67%. By the end of the infusion of IVIG on day 3 of admission, the patient had clinically improved. He was started on dipyridamole at a dose of 3 mg/kg/d. He remained well perfused, with no evidence of heart failure or myocarditis. His heart rate ranged between 60 and 100 bpm. There was evidence of seconddegree heart block on cardiac monitoring. Twenty-four-hour Holter monitoring on day 4 recorded predominantly sinus rhythm with normal heart rate range and variability for age. There was episodic first-degree AV block and second-degree Wenckebach block with no significant ectopy. There were no symptoms reported during the monitoring. The patient was discharged on day 5 of admission on dipyridamole with cardiology follow-up. Two weeks after discharge, repeat electrocardiography and 24-h Holter monitor revealed sinus rhythm with no AV block. Four weeks after discharge, echocardiography was normal. Cardiovascular examination was normal. Electrocardiographic abnormalities most commonly reported in patients with KD reflect myocarditis, pericarditis, or myocardial infarction. Such changes include tachycardia out of proportion to the degree of fever, prolonged PR and QT intervals, ST-segment and T-wave changes, and decreased R-wave voltages [1]. Most ECG changes normalize following the acute episode. Apart from sinus tachycardia, rhythm abnormalities are less commonly reported. Large, population-based studies on KD have not described arrhythmias during the acute phase. We identified few reports in the literature specifically concerning heart block or bradyarrhythmias in KD. During the acute phase of the illness, the frequency of first-degree heart block was between 30 and 60% in two studies [2,3]. In a third series, 27/75 (36%) children had ECG abnormalities which included second-degree heart block [4]. In the two studies reporting follow-up ECGs at 6 mo, the frequency of persisting abnormal ECGs was 0 and 6%, respectively [2,4]. The patient that we report presented with AV block during the acute phase and treatment of KD, with concurrent influenza A infection. All symptoms of KD, including the AV block, resolved quickly with IVIG treatment. The onset of the AV block was within a short time of commencing the IVIG infusion, but we are unaware of any reports of AV block related to IVIG. An arrhythmia secondary to influenza A infection was also considered. Myocarditis is a well recognized complication of influenza infection. The exact prevalence of AV block or ECG abnormalities in children with influenza, upper respiratory tract infection, or subclinical myocarditis is unknown, but most likely is very low [5,6]. In one study looking at the prevalence of electrocardiographic abnormalities in children with acute respiratory tract infections, which included influenza, 0 of 737 children had heart block [5]. In the patient that we report, there were no clinical signs of heart failure related to myocarditis, no evidence of ischemic changes on the ECG, or coronary aneurysms on echocardiography. Along with early diagnosis and appropriate treatment, knowledge of potential sequelae will help aid the care of children with KD. Conduction abnormal-