This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
For a patient of hypertension on metoprolol, verapamil was given. This will result in: 
Select and explain. 
A. Atrial fibrillation, B. Bradycardia with AV block, C. Torsades de pointes, D. Tachycardia
B: Bradycardia with AV block
Answer: B: Bradycardia with AV block 
Explanation: Ans. B. Bradycardia with AV block* Impulse generation in theSA node and conduction in AV node are blocked by all calcium channel blockers* Sodium channel block is modest with verapamil, and still less marked with diltiazem. It is negligible with dihydropyridines.* Verapamil and diltiazem block conduction in cardiac calcium-dependent cells (AV node) more selectively than do the dihydropyridines.* Metoprolol is selective (b1 blocker which blocks b1 receptors in heart and as a result decreases the heart rate.* So combination of metoprolol with verapamil can cause marked decrease in heart rate along with AV block effect. This combination is irrational.