Background: Multiple episodes of syncope in rapid succession are extremely rare, and syncope in the elderly has multiple potential mechanisms. Even though the electrophysiology study has little role in patients with syncope who have structurally normal hearts, the history of syncope preceded by palpitations was a red-flag symptom that made us go ahead with the electrophysiology study (EP) that revealed the ultimate diagnosis of typical atrioventricular nodal reentry tachycardia (AVNRT), which was documented to be associated with critical hypotension.

Case presentation: A 78-year-old man with a history of hypertension experienced a ‘Syncopal Storm’, with four episodes within 15 minutes. There was no history to suggest common etiologies like postural hypotension or vasovagal syncope. The examination, ECG, and echocardiogram were normal. In view of the nasty sequence and a history of syncope preceded by palpitations, we conducted an electrophysiology study. Surprisingly, typical AVNRT at 190 bpm was easily and repeatedly induced with atrial extrastimuli. During the AVNRT, the systolic BP fell from 160 mm Hg to 40 mm Hg with the development of presyncope. No ventricular tachycardia was inducible despite vigorous ventricular stimulation protocol. Radiofrequency ablation was performed successfully. The patient was symptom-free after 6 months of follow-up. 

Conclusion: We report a unique case of a syncopal storm due to AVNRT in the setting of a structurally normal heart. The syncopal storm is a rare but ominous presentation of AVNRT. The cause of syncope was a combination of a high heart rate, loss of atrioventricular synchrony, and an impaired autonomic vasomotor response, causing severe hypotension.