Electrocardiographic Abnormalities in Hypertension Models

Abstract

Background: Hypertensive condition can lead to abnormalities in heart structure and electrical activity. The electrocardiogram (ECG) is a recording of the electrical activity of the heart and widely used to diagnose and detect heart problem. Objective: We conducted a comparative ECG analysis between two hypertension models (L-NAME and SHR) and their controls (Wistar and Wistar-Kyoto) at six and 15 th week of age. Methods: Blood pressure was measured at the end of the 15 th week, and electrocardiography was performed at six and 15 weeks of age in anaesthetized rats. Data normality was confirmed by Kolmogorov-Smirnov test followed by unpaired Student's t-test and the Mann-Whitney for parametric and non-parametric data, respectively. Results are expressed as mean ± SD. The accepted level of significance was set at p < 0.05. Results: L-NAME exhibited prolongation of JT and QT intervals and SHR showed a decrease in heart rate when compared to Wistar-Kyoto and L-NAME. Wistar-Kyoto exhibited short PR interval with increased QRS complex, and only QT prolongation at 15 weeks compared to Wistar. Conclusions: All the hypertension models used in this study featured an increase in blood pressure. However, while SHR showed cardiac dysfunction, L-NAME exhibited changes in ventricular performance. These results may guide future studies on different types and models of hypertension.

Relevance of Animal Models and Echocardiogram for Hypertensive Disease Studies

“…In addition, SHR also presented higher time-to-peak values than Wystar-Kyoto rats. According to Conceição-Vertamatti et al, 6 these data are in agreement with the literature and validate the experimental models of hypertension used. No differences were observed between controls or hypertensive groups regarding the hemodynamic parameters.…”

“…Scridon et al, 7 reported unprovoked atrial tachyarrhythmias in aging spontaneously hypertensive rats correlating them with changes in the autonomic nervous system. Abdel-Rahman et al, 8 in their turn, described differences between L-NAME and Wistar rats regarding the ECG parameters similarly to Conceição-Vertamatti et al, 6 However, the latter authors highlighted the fact that none of them compared two different models of hypertension with each other on this matter.…”

“…ECG is considered a simple and inexpensive technique, being widely performed to diagnose cardiovascular diseases. 4,5 The manuscript published by Conceição-Vertamatti et al, 6 in the International Journal of Cardiovascular Sciences, proposes a comparative analysis encompassing two different experimental models of hypertension (endocrine/genetic) and their respective controls. Thus, the animals were divided into four experimental groups (6 animals/group): Wistar rats treated and untreated with L-NAME, Wistar-Kyoto rats and SHR.…”

“…Thus, depending on the experimental model, the adaptive mechanisms triggered by hypertension may be distinct. 6 Previous researches have included these two hypertensive experimental models and the evaluation of ECG tracings. Scridon et al, 7 reported unprovoked atrial tachyarrhythmias in aging spontaneously hypertensive rats correlating them with changes in the autonomic nervous system.…”

“…Although of great importance, the manuscript published by Conceição-Vertamatti et al, 6 presents a few limitations that must be briefly discussed. More accurate data could be obtained with a different strategy for oral administration of L-NAME, rather than the drinking-water approach.…”