Transient Atrioventricular Conduction Disturbances in a Case of Severe Fever with Thrombocytopenia Syndrome

A 79-year-old woman with severe fever with thrombocytopenia syndrome (SFTS) developed progressive atrioventricular (AV) conduction disturbances during hospitalization. On hospital day 6, first-degree AV block progressed to transient complete AV block, causing syncope and a 15-sec asystolic pause. Echocardiography showed preserved ventricular function, and cardiac magnetic resonance imaging did not support clinically overt myocarditis. A temporary transvenous pacemaker was inserted, and AV conduction recovered spontaneously; pacing was discontinued by day 9 without permanent pacemaker implantation. This case suggests that SFTS can cause reversible high-degree AV block and may warrant continuous twelve-lead electrocardiography (ECG) monitoring and timely temporary pacing.