De subitaneis mortibus. XI. Young girl with palpitations.

A seventeen-year-old girl in apparent good health was found dead in bed one morning. Two clinical features of note were multiple premature beats present in her electrocardiograms for several years, and a tall thin habitus without stigmata of Marfan's syndrome. At necropsy examination the heart was grossly normal. At its margin abutting the central fibrous body the atrioventricular (A-V) node exhibited numerous fronds and outcroppings, some forming loop connections from one part of A-V node to another. Groups of A-V nodal cells detached from the A-V node were also found connected to the crest of the interventricular septum. There were large connections directly from the His bundle to the crest of the interventricular septum (Mahaim fibers). The A-V node artery was moderately narrowed but patent. The possible significance of these findings in the pathogenesis of re-entrant arrhythmias or ectopic automaticity is discussed.