ABC | Volume 110, Nº4, April 2018

Original Article Impact of a High-Intensity Training on Ventricular Function in Rats After Acute Myocardial Infarction Simone de Campos Neitzke Winter, 1 Rafael Michel de Macedo, 1,4 Júlio Cesar Francisco, 1 Paula Costa Santos, 1 Ana Paula Sarraff Lopes, 1 Leanderson Franco de Meira, 1 Katherine A. Teixeira de Carvalho, 2 José Rocha Faria Neto, 1 Ana Carolina Brandt de Macedo, 3 Luiz César Guarita-Souza 1 Centro de Ciências Biológicas e da Saúde da Pontifícia Universidade Católica do Paraná (PUCPR); 1 Curitiba, PR - Brazil Instituto Pelé Pequeno Príncipe; 2 Curitiba, PR - Brazil Universidade Federal do Paraná (UFPR); 3 Curitiba, PR - Brazil Academia do Coração - Hospital Cardiológico Costantini, 4 Curitiba, PR – Brazil Mailing Address: Rafael Michel de Macedo • Rua Pedro Collere, 890. Postal Code 80320-320, Vila Izabel, Curitiba, PR – Brazil E-mail: rafael.macedo@hospitalcostantini.com.br , acbrandt@bol.com.br Manuscript received May 20, 2017, revised manuscript August 22, 2017, accepted September 14, 2017 DOI: 10.5935/abc.20180036 Abstract Background: Physical exercise should be part of the treatment of post-acute myocardial infarction (AMI) patients. Objective: To evaluate the effects of two training prescription models (continuous x interval) and its impact on ventricular function in rats after AMI with normal ventricular function. Methods: Forty Wistar rats were evaluated by echocardiography 21 days after the AMI. Those with LVEF = 50% (n = 29) were included in the study and randomized to control group (CG n = 10), continuous training group (CTG n = 9) or interval training group (ITG, n = 10). Then, a swimming test with control of lactate production was performed. Based on its result, the lactate threshold (LT) was established to define the training intensities. After six weeks, the animals were reassessed by echocardiography and lactate production. Outcome measures were end-diastolic diameter (EDD), end-systolic diameter (ESD), left ventricular ejection fraction (LVEF, %) lactate at rest, lactate without overload, and lactate with 12g and 13.5g of additional load. Group comparisons of quantitative variables of the study were performed by one-factor analysis of variance (ANOVA). The Newman-Keuls test was used for multiple comparisons of the groups. Within-group comparisons of dependent variables between the two training protocols were performed by Student’s t-test. Normality of the variables was tested by the Shapiro-Wilks test. Values of p < 0.05 indicated statistical significance. Results: EDD, ESD, and LVEF before and after the training period were similar in within-group comparisons. However, EDD was significantly different (p=0.008) in the CG. Significant differences were found for L12g (p=0.002) and L13.5g (p = 0.032) in the ITG, and for L12g (p = 0.014) in the CG. No differences were found in the echocardiographic parameters between the groups. Significant differences were found in lactate without overload (p = 0.016) and L12 (p = 0.031) in the second assessment compared with the first, and between the groups – ITG vs. CG (p = 0.019) and CTG vs. CG (p = 0.035). Conclusion: Both methods produced a training effect without altering ventricular function. (Arq Bras Cardiol. 2018; 110(4):373-380) Keywords: Myocardial Infarction; Exercise; Ventricular Function, Left; Rats; Anaerobic Threshold. Introduction Cardiovascular diseases (CVDs) are considered the main cause of death in Brazil and in the world in individuals older than 30 years, and acute myocardial infarction (AMI) is responsible for approximately 10% of these deaths. 1 Treatment after AMI should be pharmacological combined with life habit changes and exercise. Therefore, physical training plays an essential role in AMI treatment. 2 Current guidelines recommend prescription of physical exercises according to individual’s risk stratification, and the most accepted is the combination of moderate-intensity aerobic and resistance exercises. 3 However, with the progression of prescribed physical training, some authors have decided to prescribe high-intensity training for post-AMI patients. 4 Experimental studies involving high-intensity training have shown controversial results in terms of benefits to this population. 5,6 Zhang et al. 5 investigated the effects of high-intensity sprint training on post-AMI cellular adaptations. Myocytes isolated from hearts with chronic myocardial infarction had a 10% increase in length but not in width, which is consistent with hypertrophy. This may minimize ventricular remodeling and prevent the occurrence of dilated cardiomyopathy. Benito et al. 6 used an animal model to evaluate whether sustained intensive exercise training would induce structural changes in the heart. The authors reported cardiac fibrosis after long-term intensive exercise training, together with changes in ventricular function and increased arrhythmia inducibility. 373