QT-RR Relation Is Different in Humans and Rats

The QT interval (QT) variability has been recently computed to infer cardiac 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 to the preceding RR in 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) rats during the dark period. Pearson product moment correlation coefficient r computed between RR and QT was calculated for each subject or animal within 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 rats and that the strength of the QT-RR association is lower in rats. We conclude that attention should be paid when using the rat model in translational studies assessing the QT-RR relation.