Familial atrial dysrhythmia with A-V block. Intracellular microelectrode, clinical electrophysiologic, and morphologic observations.

This study is of a family with a syndrome of atrial fibrillation or flutter with advanced or complete atrioventricular (A-V) block, involving four members in two generations. Less serious arrhythmias were documented in another 15 members (three generations). Inheritance was by autosomal dominance with varying degrees of expression. An atrial biopsy was obtained in one of the members, a 40-year-old female who had atrial flutter with advanced A-V block proximal to the His bundle (H-V interval of 39 msec). Intracellular action potential (IAP) recordings from this tissue revealed: 1) partially depolarized cells with depressed IAP amplitude, 2) phase IV diastolic depolarization with spontaneous firing, 3) diminished excitability and responsiveness, and 4) decremental conduction with local block and re-entry. Histological findings revealed vacuolar degeneration, hypertrophy, and early necrosis of atrial cells. In conclusion, the multiple IAP and pathologic abnormalities provide a basis for atrial dysrhythmia in this family. The etiology of the disease is unknown.