Pharmacology Which one of the following best represents the mechanism of action and electrocardiographic effect of diltiazem? A Calcium channel blockade; increased QT interval B Adrenergic receptor blockade; decreased QT interval C Calcium channel blockade; increased PR interval D Potassium channel blockade; increased QRS duration 💡 Explanation Which one of the following best represents the mechanism of action and electrocardiographic effect of diltiazem? ✓ Correct Answer: C. Calcium channel blockade; increased PR interval