IJCS | Volume 31, Nº2, March / April 2018

180 difficult. Evidence of microcirculatory disorders as causes of anginal manifestations in this group accumulates in the literature. 11,41,42 Clinical diagnosis The diagnosis of Chagas' heart disease must be based on epidemiological criteria, clinical manifestations, serological tests and on the results of some complementary tests. Serological tests Given the low parasitaemia in the chronic phase of the disease, the serological tests must be able to detect antibodies against T. cruzi antigens. The most commonly used tests are: immunoenzymatic assay (ELISA), indirect immunofluorescence (IFI), and indirect hemagglutination (HAI). When all 3 are performed, agreement (90-98%) was observed among them. Since ELISA and IFI have similar characteristics in terms of their accuracy, with higher sensivity, but slightly reduced specificity than the HAI assay, a positive result in two of these three tests is recommended for the diagnosis. However, when the first test is negative, in the current practice based on the high sensitivity of all serological tests, there is no need for a second test. 43 Complementary cardiologic exams The main complementary diagnostic tests used in Chagas' heart disease are briefly described below, with emphasis on those focusing on the characterization and gradation of ventricular dysfunction. Electrocardiography and Holter Monitoring: The most prevalent electrocardiographic alterations in patients with CCC are right bundle branch disorders and the left anterior hemiblock, and may reach 50% in patients of this group. 44 These changes in the cardiac conduction system may be evolutionary, such as AV conduction delays. Sinus node dysfunction can also cause bradycardia. However, atrial arrhythmias tend to occur in the evolution of the heart disease with advanced ventricular dysfunction. It is crucial to observe that, although ventricular ectopic beats can be seen in normal individuals during the recording of a standard ECG, when it is verified in patients with CCC, the meaning of this alteration is completely different and it usually indicates that the ventricular arrhythmia is an integral part of the syndrome and it constitutes an element of strong prognostic value. Symptoms suggestive of arrhythmic syndromes also make ECGHolter monitoring mandatory, since it allows the assessment of episodes of both tachyarrhythmias and bradycardia for risk stratification in these patients. 34 Recording for at least 24 hours allows determining the density of ventricular ectopy, detecting episodes of nonsustainable or sustained ventricular tachycardia, as well as determining the duration of sinus pauses and of asystolia of different origins. It is worth recalling that, to compose the Rassi score, used for predicting mortality in patients with CCC, the 24-hour Holter test is essential to assess the prognostic criteria, with independent value, of nonsustained ventricular tachycardia, as it will be seen later. Other frequent changes in ECG at rest are: diffuse T wave and ST segment abnormalities, pathological Q waves, prolongation of the QT interval and increased QT dispersion. The evaluation of fibrosis using the QRS score applied to the standard ECG correlates with the NYHA functional class andwith the extent of myocardial fibrosis detected in Late Gadolinium Enhanced (LGE) cardiac magnetic resonance imaging. 45 Chest X-ray: Advanced stages of the disease are marked by (often massive) cardiomegaly, which may include signs of not only increased LV, but also of increased RV and both atrial dilation; however, pulmonary congestion differs from other cardiopathies because it is often discrete, in contrast to the degree of cardiothoracic ratio. Cardiomegaly is also an important prognostic factor in these patients, stratified by the Rassi score, as discussed next. Echocardiography: Echocardiography is a non‑invasive imaging method that allows the geometrical and functional diagnosis of both ventricles, which is essentially important in CCC. Alterations in segmental mobility in the inferior and inferolateral regions of the LV are quite common in patients with the cardiac chronic form. 46-50 Even though the detection of LV apical aneurysm (a very common alteration in patients with CCC) 51 may be subject to operational limitations, it is one of the typical changes found in the disease, and may be filled with thrombus (Figure 3, A). Although early changes in LV regional mobility can be detected on ECG, both through conventional techniques 17,52,53 and analysis of myocardial deformation, in some patients classified as having the indeterminate form, or even with CCC and function preserved by other methods, 18,53,54 the prognostic value of these alterations is not well established yet. 50,55 Simões et. al. Chagas Disease Cardiomyopathy Int J Cardiovasc Sci. 2018;31(2)173-189 Review Article