QT-RR Relation Is Different in Humans and Rats

Beatrice De Maria1, Vlasta Bari2, Beatrice Cairo3, Aparecida Maria Catai4, Anielle Cristhine de Medeiros Takahashi4, Luca Carnevali5, Andrea Sgoifo5, Francesca Perego6, Laura Adelaide Dalla Vecchia6, Alberto Porta3
1IRCCS Istituti Clinici Scientifici Maugeri, Milan, 2Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, 3Department of Biomedical Sciences for Health, University of Milan, 4Department of Physiotherapy, Federal University of São Carlos, 5Stress Physiology Laboratory, Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma; Microbiome Research Hub, University of Parma, 6IRCCS Istituti Clinici Scientifici Maugeri


Only recently the QT interval (QT) variability has been successfully exploited in rats for cardiac control assessment and it has been demonstrated that QT variability markers have a similar physiological meaning in humans and rats. However, some studies suggest that the dependence of QT on the previous RR interval (RR) might differ between humans and rats. Thus, the aim of this study was to compare the QT-RR relation in humans and rats. Electrocardiogram (ECG) was recorded for 10 minutes in supine position (REST) and during sympathetic activation induced by head up tilt test at 90° (T90) in 23 young healthy subjects (11 males, age 26.3±5.6 years). ECG was also telemetrically recorded in 9 Wistar (WI) and 14 wild-type Groningen (WT) rats during the dark period for one hour. The two rat strains are known to exhibit different social traits that are mirrored by a diverse sympathetic control. RR and QT beat-to-beat series were computed. Pearson correlation coefficient r between RR and QT was calculated for each subject, or animal, within each experimental condition. We found that r was positive in humans and decreased from REST to T90 (0.48±0.18 vs 0.34±0.25), while r was negative in rats and did not differ between WI and WT (-0.32±0.17 vs -0.26±0.18). r absolute value was significantly higher in humans than in rats (0.41±0.22 vs 0.27±0.18), when data were pooled together regardless of the experimental condition or rat strain, respectively. Our results showed that relation between QT and RR is of opposite sign in humans and rats and that the strength of the QT-RR association is lower in rats than in humans. We conclude that attention should be paid in the use of the rat model in translational studies assessing the QT-RR relation given that it can be different in humans and rats.