Auxílio ao diagnóstico e prognóstico da doença de Chagas utilizando índices da variabilidade da freqüência cardíaca e a medida de complexidade de séries RR

• Ano de defesa: 2011
• Autor(a) principal: Kathy Mendes Ferreira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Engenharia Elétrica; Engenharia elétrica
• Link de acesso: http://hdl.handle.net/1843/BUOS-8R3GPG

The discovery of Chagas disease celebrated its centenary in 2009. However, despite diagnostic and therapeutic advances achieved since the first studies of Carlos Chagas, it is estimated that there are still about 13 million people infected by the T. cruzi in Latin America and hundreds of thousands in developed countries due to international migration and faults in the control of transfusion transmission of Chagas disease. Moreover, recently, the occurrence of cases of the disease due to ingestion of acai fruit and sugarcane juice infected in Brazil attracted attention to an unknown via of infection by the parasite until then, the oral transmission of Chagas disease. After infection by Chagas disease, this manifests itself in two phases: acute and chronic. In the acute phase, which lasts about a month, the parasitemia level is high and the disease diagnosis is possible by observation of the parasite in infected blood, by microscopy. If the disease treatment is not performed in the acute phase, there is a progression to the chronic phase, whose symptoms appear, usually, ten years after infection. In the chronic period, the diagnosis is made by serologic testing and it is no longer possible by microscopy due to parasitemia low levels. However, the crossantigenicity and the susceptibility to humoral response of patients have raised doubts about the sensitivity and specificity of the disease serological diagnosis. The most important Chagas disease clinical variant is the chronic chagasic cardiopathy with arrhythmic episodes, so the analysis of electrocardiographic changes is essential to assess heart damage caused by Chagas disease. Heart Rate Variability (HRV) is an indirect measure of autonomic nervous system control over the heart. The abnormal cardiac autonomic regulation has been demonstrated in chagasic patients and such disturbance can be detected in their records even before the development of ventricular dysfunction, and at any stage of the disease, even in indeterminate and digestive forms. Therefore, the aim of this research is to propose ways of assessing the Chagas disease and its arrhythmic episodes by calculating HRV indexes and the Complexity Measure of stationary excerpts fromHolter records of three groups: control (group 0), chagasic patients with left ventricular normal function (group 1) and chaga sic patients with left ventricular dysfunction (group 2). The first method is based on the calculation of well known predetermined HRV indices and the statistical moments of the results for each group, and the distinction between groups was tested by bootstrapping and paired t-test applied on the statistical moments of the HRV indices, as well by theWelch test for the mean, F test for the variance, and againWelch test for the L-skewness and L-kurtosis of the indices. The other method, the Complexity Measure evaluation, gives the regularity and structure of excerpts of each group. The excerpts of the records were preselected by a stationary detector based on a hypothesis test under a WGN (White Gaussian Noise) model and a time-varying AR (TVAR) model. In the results, it was observed by bootstrapping and by paired t-test with significance level of 95 % that the three groups of patients are distinguishable by mean, variance, skewness and kurtosis of the HRV indices and thus useful for diagnosis and prognosis of Chagas disease. By the Welch and F tests, it was noticeable that the skewness and the kurtosis stood out in the distinction between the patient groups. The Complexity Measure allowed a distinction between groups 0 and 2, but with less evidence than that obtained by HRV indices. In future researches, these outputs will be part of the set of parameters for a classifier that may be used in diagnosis and prognosis of Chagas disease