A patient in their 40s presented to the emergency department with sudden-onset rapid palpitations at rest. The patient recalled similar episodes in the past that had terminated spontaneously. The patient’s heart rate was 210 beats/min at presentation, and blood pressure was 110/70 mm Hg. Carotid sinus massage was attempted to terminate the tachycardia but to no effect. Intravenous adenosine, 12 mg, followed by rapid saline flush was administered while recording the 12-lead electrocardiogram (ECG) in the emergency department (Figure 1).
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Narrow complex regular tachycardia is a common ECG finding in patients presenting to the emergency department with palpitations. Accurate identification of the rhythm and the mechanism of arrhythmia is imperative, as the success and complication rates after radiofrequency ablation are different. The morphology of the retrograde P wave and the response of the arrythmia to adenosine play an important role in identifying the rhythm abnormality. Ergo, adenosine acts not only as a therapeutic drug but also a diagnostic tool.
In patients with typical AVNRT, the retrograde P wave is very close to the QRS complex, thus producing short RP tachycardia with RP interval less than 70 milliseconds. Also, as the atrial depolarization travels from the AV node and above, P waves in inferior leads are negative, described as pseudo-S waves, and are positive in lead V1 and termed as pseudo-R waves.2
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CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.
Corresponding Author: Anunay Gupta, MD, DM, Department of Cardiology, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi-110029, India (firstname.lastname@example.org).
Published Online: February 7, 2022. doi:10.1001/jamainternmed.2021.7764
Conflict of Interest Disclosures: None reported.
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