IJCS | Volume 33, Nº4, July and August 2020

DOI: https://doi.org/10.36660/ijcs.20190116 Introduction Prolonged exposure to stressors can lead to changes in the adaptive systems and consequently increased circulating levels of cortisol and adrenaline. 1-3 This imbalance can result in several types of diseases, including cardiovascular diseases, which are the leading cause of death in the world. 4 The development of hypertension may be associated with sympathetic overactivity, however the underlying mechanisms that surround the pathogenesis of hypertensive disease are complex and challenging, encouraging researchers to elucidate these mechanisms. 5-7 Animal models are critical to advancements in medical research and provide valuable information regarding many aspects of the disease. 8-10 Classically, there are two well established models of sympathetic overactivity: theNG-monomethyl-L-argininemethyl ester (L-NAME)-induced hypertension and the spontaneously hypertensive rats (SHR). 10 Hypertensive condition can lead to abnormalities in cardiac structure, and consequent dysfunction in cardiac electrical activity. 11,12 The electrocardiogram (ECG) is a recording of the electrical activity of the heart and widely used to diagnose and detect heart problems. 13 This test shows typical upward and downward 321 ORIGINAL ARTICLE International Journal of Cardiovascular Sciences. 2020; 33(4):321-328 Mailing Address: Dora Maria Grassi-Kassisse Rua Monteiro Lobato, 255. Postal Code: 13083-872, Campinas, SP – Brazil. E-mail: doramgk@unicamp.br Electrocardiographic Abnormalities in Hypertension Models Ana Gabriela Conceição-Vertamatt i, F ilipy Borghi , L arissa Yuri Ishiz u, Gustavo Trevisan Cost a, L uiz Alberto Ramo s, M iguel Arcanjo Area s, D ora Maria Grassi-Kassiss e UNICAMP - Universidade Estadual de Campinas, Campinas, SP - Brazil Manuscript received on June 11, 2019, revised manuscript on September 17, 2019, accepted on September 25, 2019. 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. (Int J Cardiovasc Sci. 2020; 33(4):321-328) Keywords: Rats; Hypertension; Blood Pressure; Electrocardiography/methods; NG-Nitroarginine Methil Éster/ adverse effects; Rats, Inbred (SHR).