A 58-year-old man presented to the emergency department with sudden onset rapid palpitations and significant
presyncope while walking on the flat. The previous day he had undergone DC
cardioversion for
atrial fibrillation (AF) which had been initially successful. However, 6 h after
cardioversion he was aware of intermittently raised but regular heart rates. On arrival at the emergency department (ED) he was well with no haemodynamic compromise. The ECG showed an atrial
tachycardia instead of AF. Medications consisted of
propafenone 300 mg twice daily,
bisoprolol 5 mg at night and
warfarin.
Bisoprolol was increased to 5 mg twice daily and he was discharged with a plan for outpatient ablation. He collapsed in the hospital car park with rapid palpitations, chest tightness and vagal symptoms. On return to the ED he was hypotensive with a heart rate of 200 bpm. The ECG showed 1:1 atrioventricular conduction (AV) of the atrial
tachycardia which promptly improved after administering intravenous
atenolol. Class 1c antiarrhythmic agents such as
propafenone can precipitate 1:1 AV conduction of atrial
tachycardias resulting in dangerous exacerbations of ventricular rate or even malignant
tachyarrhythmias. It is therefore essential that concomitant AV blocking agents are used both prophylactically or acutely in suspected cases.