A man in his mid-50s with a history of mitral valve repair presented to the emergency department with complaints of recent-onset palpitation within the last hour. On physical examination, the patient showed a rhythmic tachycardia with a rate of 178 beats/min and blood pressure of 130/80 mm Hg. The 12-lead electrocardiogram (ECG) revealed a regular tachycardia with a rate of 178 beats/min; no obvious P waves were recognizable (Figure 1A). The QRS complexes displayed 2 different morphologies occurring with a definite allorhythmic distribution: pairs of beats exhibiting complete right bundle branch block (RBBB) and QRS duration of 140 milliseconds followed by a third beat with normal configuration and QRS duration of 70 milliseconds. This trigeminal variation in intraventricular conduction occurred without any change in cycle length and was maintained. Adenosine administration quickly slowed the ventricular rate allowing recognition of an atrial tachycardia with a rate of 178/min and a 2:1 atrioventricular (AV) ratio (Figure 1B).
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Corresponding Author: Vincenzo Carbone, MD, Outpatient Cardiology, via Europa, 84 S Giuseppe Vesuviano, Naples 80047, Italy (email@example.com).
Published Online: September 7, 2022. doi:10.1001/jamacardio.2022.2902
Conflict of Interest Disclosures: None reported.
Additional Contributions: We thank the patient for granting permission to publish this information.
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