امرأة عمرها ٧٤ سنة عندها رجفان أذيني، تأخذ ديلتيازيم منذ سنة، وأُضيف لها حديثاً ميتوبرولول لأن نبضها كان سريعاً. اليوم نبضها ٤٤ وضغطها ٨٨/٥٢ وتشعر بدوخة وتعب، ولم تأخذ جرعات زائدة. ما التفسير الأرجح؟

A 74-year-old woman with atrial fibrillation has taken diltiazem for a year; metoprolol was recently added for a fast rate. Today HR is 44, BP 88/52, she is dizzy and tired, and has not taken extra doses. What is the most likely explanation?

1. The combined effect of both drugs on the AV node
2. An allergy to metoprolol
3. AF improving and reverting to sinus rhythm
4. Hypokalaemia from a diuretic

Answer: A) The combined effect of both drugs on the AV node. Diltiazem and beta-blockers both slow AV conduction and depress contractility, and together they can cause marked bradycardia and hypotension. Both are held and the prescriber notified.