Vaughan Williams classification

Class Basic Mechanism Comments
1 Sodium-channel blockade Reduce phase 0 slope and peak of action potential.
1A - moderate Moderate reduction in phase 0 slope; increase APD; increase ERP.
1B - weak Small reduction in phase 0 slope; reduce APD; decrease ERP.
1C - strong Pronounced reduction in phase 0 slope; no effect on APD or ERP.
2 β-blockers Block sympathetic activity; reduce rate and conduction.
3 K+-channel blockade Delay repolarization (phase 3) and thereby increase action potential duration and effective refractory period.
4 Ca++-channel blockade Block L-type calcium-channels; most effective at SA and AV nodes; reduce rate and conduction.

Content by Dr Íomhar O' Sullivan 08/09/2016. Last review Dr ÍOS 10/06/21.