Effects of lidocaine and verapamil on early afterdepolarizations in isolated rabbit sinoatrial node.
The effects of local anaesthetic anti-arrhythmic agents (lidocaine) and Ca antagonists (Verapamil) have been examined on the early afterdepolarizations (EADs) in isolated rabbit sinoatrial (SA) node. In a nominally calcium free and magnesium free solution, strontium (0.5-4.5 mM) produced an EAD in small pieces isolated from the SA node. The additional presence of 0.02-0.6 mM lidocaine did not abolish the strontium (0.5 mM)-induced EAD. 0.6 mM lidocaine produced an increase in EAD amplitude and then abolished a prolonged action potential (AP) associated with repetitive EADs. On the other hand, the addition of 4 micro M verapamil abolished the strontium (0.5 mM)-induced EAD but did not abolish the AP.It is concluded that under conditions when the AP is not abolished, EAD blockade by lidocaine is less effective than that by verapamil.
Department of Anesthesiology, Kanazawa Medical University, Ishikawa, Uchinada, Japan.
S
S
Miyamae
T
T
Matsuda
K
K
Goto
H
H
Mori