Irregular Narrow Complex Tachycardia

Abstract

A woman in her 40s with a medical history of infective endocarditis and hepatitis C secondary to ongoing intravenous drug use presented to the emergency department with severe back pain and evidence of vertebral osteomyelitis/diskitis. She was hospitalized and treated for Staphylococcus aureus bacteremia. Transesophageal echocardiography findings revealed pulmonic valve vegetations and severe tricuspid valve regurgitation secondary to a flail leaflet. She underwent 6 weeks of intravenous antibiotic treatment and subsequent tricuspid valve replacement with a 29-mm bioprosthetic Carpentier-Edwards valve complicated by transient third-degree heart block. Two days after pacemaker placement, she had episodes of light-headednessandchestpainwithheartratesbetween150and190beats per minute. Her blood pressure was 94/60 mm Hg. The electrocardiogram during tachycardia is presented in Figure 1.Question: What is the rhythm demonstrated on the electrocardiogram? InterpretationThe P waves are upright in leads II, III, and aVF, suggesting an origin in the sinus node with a rate of 96 beats per minute. Grouped beating is apparent, with 1 P wave producing 2 QRS complexes, giving rise to the regularly irregular rhythm. This pattern is diagnostic of dual atrioventricular (AV) nonreentrant tachycardia.

Differential Diagnosis for Electrocardiography Challenge—Reply

“…In Reply This letter is written as a reply to the astute Letter to the Editor written by Mahabala and colleagues offering atrial bigeminy as another differential diagnosis regarding a regularly irregular narrow complex tachycardia presented in our Challenge in Clinical Electrocardiography . The authors interpret the electrocardiogram (ECG) presented in the article and highlight the possibility of atrial bigeminy with a sinus P wave with a PR interval of 240 milliseconds followed by an ectopic P wave with a shorter PR interval of 160 milliseconds, as summarized in their ladder diagram.…”

“…We thank the authors for their expansion of the differential diagnosis, and we do not have an atrial electrogram on electrophysiologic study or an atrial lead from a device interrogation during tachycardia to reference as a gold standard. With proof of a slow pathway, no discernable P waves during the short RR interval, and that the early beats should actually conduct with a longer PR interval, we favor dual atrioventricular nodal nonreentrant tachycardia over atrial bigeminy …”

Differential Diagnosis for Electrocardiography Challenge

“…To the Editor This letter is in reference to the Challenge in Clinical Electrocardiography by Choxi et al describing an irregular narrow complex tachycardia. The article described an interesting and unusual case of occurrence of dual atrioventricular nodal nonreentrant tachycardia and the need to differentiate it from atrial fibrillation.…”

“…Our understanding of the ECG in the article is that it shows the presence of sinus node P waves prior to the first beat of the bigeminy, with a PR interval of 240 milliseconds, and then an ectopic P wave with a shorter PR interval (160 milliseconds) preceding each second beat. We believe there is a strong possibility of this being an atrial bigeminy with tachycardia, as we observe 2 different morphologies of the P wave and 2 different PR intervals, which is the hallmark of atrial bigeminy .…”