EFFECTS OF LIGNOCAINE ON DISPERSION OF REPOLARIZATION AND REFRACTORINESS IN A WORKING RABBIT HEART MODEL OF REGIONAL MYOCARDIAL-ISCHEMIA

The aims of this study were to establish a working rabbit heart model of regional myocardial ischaemia in which electrophysiologic parameter s and arrhythmogenesis could be correlated and to explore the mechanis ms underlying the antiarrhythmic activity of lignocaine. Monophasic ac tion-potential duration (MAPD(90)), effective refractory period (ERP), and conduction delay were measured at three ventricular sites in isol ated hearts paced at 3.3 Hz. The hearts were treated before and throug hout 30 min of ischaemia and 15 min of reperfusion with a vehicle or 2 0 mu M lignocaine. In both groups, ischaemia produced a similar shorte ning in MAPD(90). Lignocaine decreased ERP shortening during ischaemia from -56 +/- 4 to -32 +/- 6 ms. An ischaemia-induced increase in cond uction delay was greater in the lignocaine than the control group (49 +/- 7 vs. 11 +/- 2 ms). Ischaemia-induced dispersion of repolarisation was reduced by lignocaine from 66 +/- 4 to 32 +/- 7 ms, and dispersio n of refractoriness was decreased from 57 +/- 6 to 16 +/- 3 ms. Lignoc aine decreased inducibility of ventricular fibrillation (VF) during is chaemia from 86 to 25%. We conclude that, in this model, the antiarrhy thmic activity of lignocaine during regional ischaemia is associated w ith an increase in ischaemia-induced conduction delay and reduced disp ersion of repolarisation and refractoriness.