Sinus bradycardia and atrial fibrillation associated with the Wolff-Parkinson-White syndrome

Thirty-three patients with atrial fibrillation associated with the Wolff-Parkinson-White (WPW) syndrome were studied to determine the relation of sinus bradycardia and atrial fibrillation. In seven patients the sinus rate was less than 40 beats/min and sinus nodal disease was considered a cause of the periods of bradycardia. Ventricular fibrillation or functional cardiac arrest was documented in four instances. Twenty-six patients demonstrated a type A and seven a type B WPW pattern during periods of sinus rhythm. Male patients predominated. The average age was 38.5 years among patients with a type A pattern compared with 25.3 years among those with a type B pattern. The shortest R-R cycle length in this group was 130 msec during a period of atrial fibrillation. Five thousand serial microscopic sections were studied in one patient who demonstrated ventricular fibrillation. Three anomalous pathways were located in this patient with the widest tract, 380 μ, containing about 400 muscle cells. Most of the sinoatrial node was replaced by collagen elastic fibers, and there was widespread destruction of the atria with a marked increase in fibrous connective tissue.Ventricular fibrillation or functional cardiac arrest is not a rare arrhythmia in patients with atrial fibrillation associated with the WPW syndrome and may be responsible for sudden death in patients with these arrhythmias. Hence, precise electrophysiologic studies and pharmacologic or surgical management, or both, are suggested to prevent sudden death in patients with short refractory periods associated with atrial fibrillation and the WPW syndrome.