An intriguing case of supraventricular tachycardia and a "deadly" cure.

A 62-year-old man was admitted to the emergency department due to sudden onset palpitations and chest discomfort. He denied syncope, dyspnea, and other relevant symptoms. Past medical history was relevant for excessive alcohol intake and a previous diagnosis of hypertension. The patient wasmedicatedwith 20mg of lisinopril daily. Physical examination at admission revealed blood pressure of 170/99 mmHg, heart rate of 140 bpm with no signs of hypoperfusion nor peripheral congestion. Cardiac auscultation revealed tachycardia without murmurs and pulmonary auscultation was normal. A 12-lead electrocardiogram was taken at admission, revealing a regular narrow-QRS tachycardia (Figure 1). The emergency physician decided to administer an intravenous drug, which almost immediately caused a decrease in the cycle-length (CL) of the tachycardia, culminating in very rapid heart rate (290 bpm) and hemodynamic collapse of the patient, with loss of consciousness. A rhythm strip was taken during drug administration (Figure 2). The patient was immediately submitted to emergent synchronized electrical cardioversion, which restored sinus rhythm.