LAUSR

A 23-year-old woman with Ebstein anomaly gave birth to her first healthy-born baby and subsequently developed recurrent episodes of regular wide QRS complex tachycardia (WQRST) with a left bundle-branch block (LBBB) morphology (≈140 bpm) (Figure 1). A diagnosis of supraventricular tachycardia with aberration was made, and she was given intravenous adenosine that promptly terminated the tachycardia. However, the tachycardia recurred multiple times and usually ended spontaneously within <1 minute. During normal sinus rhythm, the PR interval was normal (0.13 s), and the QRS complexes exhibited a right bundle-branch block morphology with left anterior hemiblock. Inverted T waves were present in the right precordial leads (V1 through V3). All episodes of WQRST had a pattern of LBBB with left-axis deviation (Figure 1) and showed a late precordial transition (R/S>1) in lead V5. The first QRS complexes of the WQRST occurred at varying coupling intervals, had a morphology identical to the subsequent regular WQRST, and were not preceded by atrial activity. A retrograde atrial activity with a short RP was noted following the first beat of the tachycardia, whereas the subsequent 1:1 retrograde atrial activity was associated with a longer and constant RP interval. The WQRST occasionally terminated with a similar premature complex that did not conduct retrogradely to the atrium. Variably coupled LBBB extrasystoles identical in morphology to the WQRST were also frequently documented after tachycardia ended (Figure 1). The patient was taken to the electrophysiology laboratory. What is the diagnosis and mechanism of the WQRST? Please turn the page to read the diagnosis. Anat Milman, MD, PhD Eyal Nof, MD Bernard Belhassen, MD