Correlation between QT interval and RR interval on epicardial electrogram in anesthetized open-chest dog was studied. The aortic blood pressure was kept above 70mmHg during the course of the experiment. RR interval was changed by left atrial pacing in the range of 0.243-0.870sec (0.412±0.119, mean±SD). In association with the change in RR interval, QT interval varied in the range of 0.190-0.360sec (0.253±0.028). The relation of QT interval to RR interval was statistically significant (r=0.744, p<0.01), though QT interval varied widely when the heart rate was under 100beat/min. QT interval correlated more closely to √RR interval than RR interval. The correlation equation was as follow: QT interval(sec)=0.24√RR interval (sec)+0.102, r=0.760, p<0.01. The data suggest that QT interval obtained by epicardial electrogram would be of use as an index of local electrical systole.
anesthetized open-chest dog