Sodium and potassium channel blockade

Q: Blockade of sodium channel leads to prolongation of QT interval on EKG?

A) True

B) False

Answer: B

The rule of thumb is

• Sodium channel blockade causes prolongation of the QRS interval
• Potassium channel blockade causes prolongation of the QT interval

Cocaine is a classic example of sodium channel blockade. and antipsychotics are classic examples of potassium channel blockade.

#cardiology

References:

1. Roden DM, George AL Jr. Structure and function of cardiac sodium and potassium channels. Am J Physiol. 1997 Aug;273(2 Pt 2):H511-25. doi: 10.1152/ajpheart.1997.273.2.H511. PMID: 9277464.

2. Balser JR. The cardiac sodium channel: gating function and molecular pharmacology. J Mol Cell Cardiol. 2001 Apr;33(4):599-613. doi: 10.1006/jmcc.2000.1346. PMID: 11273715.

3. Starmer CF, Reddy MR, Namasivayam A, Singh M. Potassium channel blockade amplifies cardiac instability numerical studies of torsades de pointes. Indian J Physiol Pharmacol. 1994 Oct;38(4):259-66. PMID: 7883289.