[The electrophysiologic effect of atenolol and nitrendipine on normal and ischemic rabbit myocardium in situ. II. Effects on effective refractory periods and its dispersion].

ABSTRACT

The study was carried out to determine the effective refractory period (ERP) in central part of ischemic region (CR), boundary of ischemic region (BR) and nonischemic region (NR), after occlusion of left ventricular branch of coronary artery in rabbit heart. The results turned out to be that atenolol produced significant prolongation of ERPs in all three regions before and after ligation of the coronary branch. Atenolol also caused significant reduction in dispersion of ERPs in ischemic heart. Nitrendipine, on the other hand, had no significant effects of all the parameters determined. We also found that slight changes in the absolute value of ERPs would result in much more greater changes in dispersion. So it could be inferred that the dispersion in ERPs among different regions of heart is of greater importance to the genesis and interruption of arrhythmias than ERPs themselves. Lastly, our results supported the view that there is a boundary region surrounding the central part of ischemic region, in which cells were moderately damaged and could be saved by proper treatment.