ABC | Volume 111, Nº1, July 2018

Original Article Effects of Coexistence Hypertension and Type II Diabetes on Heart Rate Variability and Cardiorespiratory Fitness Daniela Bassi, 1 Ramona Cabiddu, 2 Renata G. Mendes, 2 Natália Tossini, 2 Vivian M. Arakelian, 3 Flávia C. R. Caruso, 2 José C. Bonjorno Júnior, 4 Ross Arena, 5 Audrey Borghi-Silva 2 Departamento de Fisioterapia, Universidade Ceuma, 1 São Luís, MA - Brazil Departamento de Fisioterapia, Universidade Federal de São Carlos, 2 São Carlos, SP - Brazil Departamento de Fisioterapia, Universidade Nove de Julho, 3 São Paulo, SP - Brazil Departamento de Medicina, Universidade Federal de São Carlos, 4 São Carlos, SP - Brazil Departamento de Fisioterapia, Universidade de Illinois em Chicago, 5 Chicago, IL - EUA Mailing Address: Daniela Bassi • Rua Francisco Marigo, 1188 - Jardim Cruzeiro do Sul, Postal Code 13.572.090. São Carlos, SP - Brazil Email: danielabassifisio@gmail.com Manuscript received September 13, 2017, revised manuscript December 26, 2017, accepted March 14, 2018 DOI: 10.5935/abc.20180105 Abstract Background: Type 2 diabetes Mellitus (T2DM) is associated with cardiac autonomic dysfunction, which is an independent predictor of mortality in chronic diseases. However, whether the coexistence of systemic arterial hypertension (HTN) with DMT2 alters cardiac autonomic modulation remains unknown. Objective: To evaluate the influence of HTN on cardiac autonomic modulation and cardiorespiratory fitness in subjects with DMT2. Methods: 60 patients of both genders were evaluated and allocated to two groups: DMT2 patients (n = 32; 51 ± 7.5 years old) and DMT2 + HTN patients (n = 28; 51 ± 6.9 years old). RR intervals were obtained during rest in supine position. Linear and nonlinear indices of heart rate variability (HRV) were computed using Kubios HRV software. Pulmonary gas exchange was measured breath-by-breath, using a portable telemetric system during maximal incremental exercise testing on a cycle ergometer. Statistical analysis included Shapiro-Wilk test followed by Student’s t Test, Pearson correlation and linear regression. Results: We found that patients in the DMT2+HTN group showed lower values of mean RR intervals (801.1 vs 871.5 ms), Shannon entropy (3 vs 3.2) and fractal dimension SD 1 (9.5 vs 14.5), when contrasted with patients in the DMT2 group. Negative correlations were found between some HRV nonlinear indices and exercise capacity indices. Conclusion: HTN negatively affects the cardiac autonomic function in diabetic patients, who are already prone to develop autonomic dysfunction. Strategies are need to improve cardiac autonomic functionality in this population. (Arq Bras Cardiol. 2018; 111(1):64-72) Keywords: Hypertension/prevalence; Diabetes Mellitus,Type 2; Cardiovascular Diseases; Risk Factors; Autonomic Nervous System; Heart Rate. Introduction The prevalence of hypertension in patients with type 2 diabetes mellitus (T2DM) is up to three times higher than in patients without T2DM. 1 The coexistence of hypertension and diabetes significantly increases the probability of developing cardiovascular disease (CVD). 2 The harmful association of these two conditions may cause deleterious effects on the cardiovascular system, accelerating the atherosclerosis process involved in both T2DM and hypertension. 3 In addition, it is well known that cardiac autonomic neuropathy (CAN), resulting from damage to the autonomic nerve fibers that innervate the heart and blood vessels, is a serious complication of T2DM 4 and systemic arterial hypertension (HTN). 5 The autonomic nervous system plays a significant role in the circulatory system and in blood pressure regulation. 6 Damage to the nerve fibers that innervate the heart and blood vessels leads to abnormalities in heart rate (HR) control and vascular dynamics. 7 Heart rate variability (HRV) analysis is a widely used tool to assess the cardiac autonomic regulation. 8 HRV is commonly analyzed using linear models, such as time domain and spectral analysis; however, non-linear methodologies have been recently proposed as novel tools to investigate the complexity of HR dynamics. 9 It has been widely documented that reduced HRV is associated with various pathological conditions, including CVDs, such as hypertension 10 and diabetes. 11 However, despite the evidence that HRV is reduced in the presence of one of these conditions, it remains unknown whether HRV is altered in the coexistence of T2DM and HTN. 64