We studied a syndrome involving a progressive atrioventricular conduction defect in three generations of a large family. Clinical findings included a slow heart rate, episodes of lightheadedness, syncope, and absence of predisposing acquired or hereditary cardiac disorders. Electrocardiography showed a prolonged atrioventricular conduction with onset usually in the 30s, loss of R waves in the right precordial leads, and arrhythmia that occurs only as a late manifestation. Progression from first-degree to complete heart block was usually slow, but occasionally a fulminant course led to sudden death within two or three years. Specific differences from other forms of conduction defects suggest that this is a new hereditary syndrome.
Lynch HT, Mohiuddin S, Sketch MH, Krush AJ, Carter S, Runco V. Hereditary Progressive Atrioventricular Conduction DefectA New Syndrome?. JAMA. 1973;225(12):1465–1470. doi:10.1001/jama.1973.03220400011003