Familial Atrial Dysrhythmia withA-VBlock

SUMMARY Thisstudy isofa family with a syndrome ofatrial fibrillation or flutter withadvanced or complete atrioventricular (A-V) block, involving fourmembers intwogenerations. Lessserious arrhythmias were documented inanother 15members (three generations). Inheritance was byautosomal dominance with varying degrees ofexpression. Anatrial biopsy was obtained inone ofthemembers, a 40-year-old female whohadatrial flutter withadvanced A-Vblock proximal totheHisbundle (H-Vinterval of39msec). In- tracellular action potential (IAP) recordings fromthis tissue revealed: 1)partially depolarized cells with depressed IAPamplitude, 2)phase IVdiastolic depolarization with spontaneous firing, 3)diminished ex- citability andresponsiveness, and4)decremental conduction withlocal block andre-entry. Histological findings revealed vacuolar degeneration, hypertrophy, andearly necrosis ofatrial cells. Inconclusion, themultiple IAPandpathologic abnormalities provide abasis foratrial dysrhythmia inthis family. Theetiology ofthedisease isunknown.