The effects of selective brain cooling on E. C. G. were studied on dogs. The method applied was entirely the same as Kimoto described. Rectal temperature of dogs were kept at 31°C and brain temperature at around 19°C. In two dogs inflow tracts of heart were occluded and in another three further intracardiac manipulation were performed. E. C. G. were taken continuously during cooling, cardiac inflow occlusion and after release of occlusion. The following alterations in E. C. G. were noticed. (1) Changes during cooling Prolongation of R-R, P-Q, and Q-T intervals were marked compared to in the case of general hypothermia. QRS widened markedly and R wave appeared in earlier stage than in the latter. R wave was rather depressed instead of increase of amplitude which was seen in the case of general hypothermia. There were found no marked changes in R, Q and S waves as in the latter. Invertion of T occurred but no depression of ST segments were observed. (2) Changes during inflow tract occlusion Within ten to fifteen minutes following the occlusion R-R was markedly prolonged, R wave markedly depressed, QRS widened and T wave elevated. After release of occlusion these changes returned to normal. No marked prolongation of P-Q was seen though P(E)Q(A) was markedly depressed and concomitant depression of P wave occurred in leads II and III. Q-T was rather shortened compared to before occlusion. No marked alterations of ST segments were seen.
Temporary ventricular premature beats appeared after release of occlusion in one dog. (3) Changes during intracardiac manipulation
Two of three dogs on which intracardiac manipulation were attempted died of ventricular fibrillation at the end of manipulation. One survived the experiment though he developed complete atrio-ventricular dissociation at the end of intracardiac manipulation.