The effects of lidocaine on the ventricular fibrillation threshold and primary ventricular fibrillation following acute experimental coronary occlusion

Experiments were performed on 39 anaesthetized open-chest dogs (BW 16–33 kg) to examine the effect of lidocaine on the frequency of primary ventricular fibrillation (VF) and the time course of the ventricular fibrillation threshold (VFT) (train of stimuli-method) following acute coronary artery occlusion, and also to study the effects of lidocaine on the VFT of non-ischaemic heart at different therapeutic and high non-therapeutic doses. At effective plasma levels of lidocaine usually reached in clinical therapy (130–480 μg/l) there was no measurable increase in VFT compared to control values. The drop in VFT following acute ligation of the left anterior descending coronary artery (LAD) was neither eliminated nor even merely diminished. After occlusion of the left circumflex coronary artery (CIR), the incidence of spontaneous VF was not reduced in comparison to a control group. With regard to the doses administered and the plasma levels of lidocaine achieved, only the application of clinically extremely high or toxic doses resulted in increases in VFT in the non-ischaemic heart. Therefore it cannot be expected that there exists a protective effect of clinically recommended doses of lidocaine in preventing primary VF during the early phase of arrhythmia following acute coronary occlusion.