In order to investigate the differences of cellular electrophysiologic changes between laser photocoagulation（LP） and radiofrequency ablation（RFA）

transmembrane potentials were recorded at 0 5

1

3

5

8 mm from lesions before and after LP and RFA had been performed respectively on 15 endocardial tissues removed from 15 adult rabbits in each group Resting potential（RP）

action potential amplitude（APA）

maximum rate of upstroke velocity （dV/dT）

and action potential duration at 50 percent of repolarization（APD50） decreased at 0 5

1

3 mm from lesions in RF

so did all of them at 0 5

1 mm in LP

but all transmembrane potential variables were almost normal at 3 mm in LP Furthermore

almost all the transmembrane potential variables at 0 5 1

3 mm in RFA went down much lower than those in LP（P<0 01） There was no difference in all transmembrane potential variables at 5

8 mm between LP and RFA APD 90 had no difference at varing distance in both the groups Electrophysiologic abnormalities of border zone of injured but nonnecrotic myocardium around the lesions of laser photocoagulation are much less than those of radiofrequency ablation in strength and much smaller in scope

which suggest that unfavorable effects of laser photocoagulation on hemodynamics and arrhythmogenicity would be less than those of radiofrequency ablation