Dissimilar atrial rhythms in a patient with the Wolff-Parkinson-White syndrome

In this report, we present the findings in a patient who had paroxysmal supraventricular tachycardia and atrial flutter associated with the Wolff-Parkinson-White syndrome. During atrial flutter, localized atrial fibrillation was recorded in the coronary sinus (dissimilar atrial rhythms), near the accessory pathway; and during 90 minutes of observation, ventricular activation occurred solely over the normal pathway. We postulate that localized atrial fibrillation repetitively invaded the accessory pathway and rendered it refractory to conduction by flutter impulses.