From a Runny Nose to a Slow Heart: A Case Report About Disentangling the Mystery of A Heart Block Secondary to Influenza

Respiratory tract infections are frequently seen in children, with influenza responsible for the majority of hospital visits. While the respiratory manifestations of influenza are well recognized and managed by pediatricians, cardiovascular complications such as myocarditis, pericarditis, and conduction abnormalities are less commonly encountered and often overlooked. These complications, though rare, can have serious clinical implications if not promptly identified and treated. Here we present a rare case of influenza-induced third-degree heart block, which responded to dexamethasone therapy. A seven-month-old male child presented with fever, cough, rhinorrhea, and increased work of breathing. The child was initially managed as a case of pneumonia with intravenous antibiotics and supportive therapy. The findings from a chest radiograph were suggestive of viral pneumonia. With negative blood cultures and normal inflammatory markers, antibiotics were discontinued. Hemagglutinin Type 1 and Neuraminidase Type 1 (H1N1) influenza was confirmed on reverse transcription polymerase chain reaction (RT-PCR) testing. Though there was an improvement in the respiratory signs and symptoms, the child developed bradycardia with hypotension. Electrocardiography revealed a third-degree atrioventricular block with ST-T changes, normal cardiac structure, and preserved left ventricular function. Cardiac biomarkers were within normal limits. Despite the initiation of isoprenaline for persistent bradycardia, no improvement was seen. A short course of dexamethasone was administered, following which the child's cardiac rhythm reverted to the normal sinus rhythm. This case underscores the importance of considering cardiovascular complications, like conduction abnormalities, in children presenting with an influenza-like illness. Early recognition and timely corticosteroid therapy might restore normal cardiac conduction and potentially prevent the need for invasive interventions like the placement of a pacemaker.