BIOM3010 Lecture Notes - Lecture 4: Cardiac Action Potential, Atrial Flutter, Sotalol
Document Summary
Lecture 4 - dysrhythmias and anti-dysrhythmic drugs ii. Class 1b drugs (tend to be more specific for na channels than 1a) Bind to alpha subunit of sodium channels to prevent na entry and reducing rate of depolarisation during phase 0. Display use-dependent block the more frequently the channels are activated the greater the degree of block produced. Lie midway between 1b (fastest) and 1c (slowest) in terms of binding speed. They slow phase 0 of the cardiac action potential and increase the refractory period. Disopyramide used in life threatening ventricular tachyarrhythmias that are refractory to other tx. Rapidly associate and dissociate from na+ channels and have limited effects on conduction velocity (not good for ars) Lignocaine binds to both activated and refractory channels. Has greater effects of depolarized tissues, and limited actions on sa/atrial tissue. Associate/dissociate much more slowly reach level of steady- state block (minimal variation throughout the cardiac cycle) Has greater effect on slowing ventricular conduction system.
