QT-RR relation is different in humans and rats

The QT interval (QT) variability has been recently computedto infercardiac control of rats. It has been suggested that QT variability markers in rats have the same physiological meaning as in humans. However, some evidences indicate a different dependence of QT on the previous RR interval (RR).Thus, the aim of this study was to compare the relation of the QT tothe precedingRRin humans and in rats. Electrocardiogram was recorded in supine position (REST) and during tilt test (T90) in 23 healthy subjects and in 9 Wistar (WI) and 14 wild-type Groningen(WT) ratsduring the dark period. Pearson product moment correlation coefficient rcomputed between RR and QT was calculated for each subject or animalwithin each experimental condition.In humans we found that r was positive and decreased from REST to T90. Conversely, r was negative in rats and did not differ between WI and WT. The r absolute value was significantly higher in humans than in rats. Our results showed that trends toward longer RRs lead to longer QTs in humans but shorter QTs in ratsand that thestrength of the QT-RR associationis lower in rats. We conclude that attention should be paid when using the rat modelin translational studies assessing the QT-RR relation..