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What is The antiarrhythmic drug which decreases both rate of depolarization (phase 0) as well as rate of repolarization of myocardial fibres is and explain in detail?
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