This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
The antiarrhythmic drug which decreases both rate of depolarization (phase 0) as well as rate of repolarization of myocardial fibres is 
Select and explain. 
A. Verapamil, B. Quinidine, C. Propranolol, D. Lignocaine
B: Quinidine
Answer: B: Quinidine 
Explanation: QUINIDINE Mechanism of action:- Quinidine blocks myocardial Na+ channels in the open state--reduces automaticity and maximal rate of 0 phase depolarization in a frequency dependent manner. Prolongation of APD is due to K+ channel block, while lengthening of ERP is caused by its moderate effect on recovery of Na+ and K+ channels. At high concentrations it also inhibits L type Ca2+ channels. ECG:- Quinidine increases P-R and Q-T intervals and tends to broaden QRS complex. Changes in the shape of T wave may be seen reflecting effect on repolarization. Ref:- kd tripathi; pg num:-529