Transient complete heart block complicating acute rheumatic fever.

First-degree heart block is a common electrocardiographic manifestation of acute rheumatic fever and is included in Jones' diagnostic criteria. Other electrocardiographic changes such as sinus tachycardia, bundle branch blocks. nonspecific ST-T wave changes, atrial and ventricular premature complexes have been reported with variable frequency. However, complete heart block is an exceptionally rare manifestation of acute rheumatic fever. We report the clinical course of a 16-year-old boy with acute rheumatic fever who had prolonged P-R interval in the electrocardiogram on admission which subsequently progressed to complete heart block. The patient regained normal sinus rhythm within a few minutes without any pharmacologic or electrical intervention.