De Subitaneis mortibus. XVI. Intractable tachycardia in infancy.

Intractable tachycardia in a boy proved fatal at the age of one year. A cousin still living has the same problem. Special electrocardiographic studies in the boy demonstrated a consistent abnormality which included complete atrioventricular dissociation with a normal atrial rate but a ventricular rate usually about 240 beats/minute; a His bundle comples preceded each QRS and all QRS complexes were narrow and uniform in configuration without a delta wave. At postmortem examination there were changes due to congestive failure and the heart was enlarged but otherwise normal except for the His bundle. In its midportion the His bundle was split into several thin and irregular longitudinally oriented strands, within which there were many areas of focal degeneration. There was no myocarditis and no focal degeneration elsewhere in the heart. Although the etiology of this process is uncertain, some possibilities are discussed.