Lorena Cuenca Bermejo¹, Valeria Gonçalves², Emiliano Fernández¹, María Josefa Fernández Del Palacio³, Maria Trinidad Herrero Ezquerro¹

(1) NEUROCIENCIA CLÍNICA Y EXPERIMENTAL, IMIB-Arrixaca, España
(2) Departamento de Neurologia e Neurocirurgia, Universidade Federal de São Paulo, Brasil
(3) Hospital Clínico Veterinario Universidad de Murcia, España (Región de Murcia)

Ischemic heart disease is the leading cause of death in the world. Importantly, cardiac changes can precede other age-related disorders; therefore, diagnosing and monitoring the heart is important and it could improve the patient's prognosis, increasing the quality of life. The availability of experimental models is crucial for the understanding of the pathology and the therapies’ design. In this line, the Octodon degus has been proposed as a relevant tool for biomedical research, since it shares some similarities with the human biology and it spontaneously develop some age-related treats. Thus, the aims of this study were to determine the normal surface ECG parameters in the O. degus and to evaluate the effect of age and sex on them.

A total of 98 O. degus were divided regarding age and sex: i) young, ii) adult, iii) old, and iv) senile; both males and females. Electrocardiograms were recorded in the animals under anesthesia, and the duration and amplitude of the ECG waves were measured. Using the lead II the following variables were measured (Figure 1A): amplitude and duration of the P waves, PQ interval duration, QT interval duration, amplitude and duration of the QRS complex, presence of ST segment, elevation or depression, amplitude of the T wave we also calculated heart rate and electrical axis.

Some ECG parameters were age-dependent: i) heart rate values reached their maximum value in adult animals (1 year old) and decreased with age (Figure 1B); ii) we observed differences in the pattern of the duration of P wave when females and males were compared, since as the age increases, the duration of P wave increases in females, while in males it decreases (Figure 1C); iii) regarding R wave voltage, values for males were slightly lower than those of females (Figure 1G); iv) the values for the S wave amplitude were higher in the males than in the females (Figure 1H). On the other hand, other parameters seemed to be strongly influenced by the age of the animal: i) the duration of the QRS complex of old and senile females was significantly increased when it was compared with the young groups (Figure 1F); ii) regarding S amplitude, significant differences were found when adult males were compared with females of the same age (Figure 1H); ii) QT interval we identified a significant decrease in its duration when adult males were compared with the young ones (Figure 1J). Finally, arrhythmias and electrical axis deviation were more frequent in males than in females (Figure 2).

This study characterizes for the first time the electrocardiographic parameters in both sexes of the O. degus during the aging process, from young to senile animals.The data obtained showed spontaneous cardiac alterations within the age that differs in females and males, which is a strong point to consider the degus as a natural model for cardiovascular research since its shares some features with the human aging.