Pseudo‐Wenckebach

Abstract

A 47-year-old man with an implanted dual-chamber pacemaker was transferred to the emergency department with acute onset shortness of breath. He had tachycardia, with a heart rate of 123 beats/min in a regularly irregular rhythm. His respiratory rate was 30 breaths/min, and oxygen saturation was 88% with 15-L oxygen via a mask with a nonrebreathing reservoir. The chest X-ray showed bilateral perihilar airspace opacity with dilatation of the main pulmonary artery. An electrocardiogram (Fig. 1A) showed wide-complex tachycardia with regularly irregular RR intervals induced by progressive prolongation of the AV interval. Based on the clinical presentation, a diagnosis of acute pulmonary edema was made. This progressive prolongation of the AV delay is often called “pseudo-atrioventricular Wenckebach.” The pseudo-Wenckebach occurs when the sinus rate exceeds the programmed maximum tracking rate, but the P–P interval is longer than the total atrial refractory period to avoid an abrupt decrease of the ventricular rate that results in circulatory disruption.1, 2 When physicians find irregular P–Q interval, the pseudo-Wenckebach is sometimes mistaken for pacing failure. Therefore, emergency physicians should know this phenomenon. After recovery within a day on nitrates and diuretics, the electrocardiogram (Fig. 1B) showed a normal pacing rhythm. Approval of Research Protocol: Not applicable. Informed Consent: Not applicable . Registry and the Registration No. of the study/Trial: Not applicable. Animal Studies: Not applicable. Conflict of Interest: None declared.