Estudo das adaptações hemodinâmicas da miocardiopatia chagásica pela curva de volume do ventrículo esquerdo obtida pelo ecocardiograma tridimensional

Abstract

Three-dimensional echocardiography allows volume calculation of the left ventricle throughout the cardiac cycle, making it possible to construct a volume-time curve. This method is more accurate than two-dimensional echocardiography because the construction of left ventricular volume is performed by the analysis of hundreds of points at the edge of the endocardium, without using any specific plane or geometric model to describe the complex structure of the left ventricle. In this paper, we test the hypothesis that it is possible to study the hemodynamic adaptations of non-invasively Chagas cardiomyopathy by the volume-time curve generated by three-dimensional echocardiography. Thus, the objective of this study was to study, in a crosssectional study, left ventricular function, using volume curve in patients with Chagas cardiomyopathy when compared with healthy individuals. From the volume curve, we identified left ventricular end-diastolic and end-systolic volumes and stroke volume. Then, using a program developed in MATLAB software, we constructed the flow curve in all patients using the polynomial method. We identified the absolute maximum flow value during systole and its correction for left ventricular end-diastolic volume, early filling phase and during atrial contraction. Twenty patients with Chagas cardiomyopathy, mean age of 45 ± 12 years, 55% of males, were compared with 15 gender and age matched healthy controls. Most patients (70%) had exertional dyspnea, on treatment for heart failure, mainly using the angiotensin-converting enzyme inhibitor and beta-blockers. Patients with Chagas cardiomyopathy had a greater LV end-diastolic and end-systolic volumes, and lower LV ejection fraction compared to the control group. However, the stroke volume and maximum ejection flow during systole were similar between groups. The group with Chagas cardiomyopathy had lower systolic flow corrected for left ventricular end-diastolic volume compared to the control group. The flow in the early filling intervals and atrial contraction were similar between the groups, as well as the respective velocity measurements at the tip of the mitral valve leaflets, E and A waves. As expected, patients with Chagas cardiomyopathy showed an increase in preload compared to the control group, as demonstrated by the increment in left ventricular end-diastolic volume and E / e 'ratio. In conclusion, the results of our study demonstrated that peak systolic flow and stroke volume were similar among patients with severe ventricular dysfunction due to Chagas cardiomyopathy and healthy controls. Using a non-invasive tool for the first time in Chagas cardiomyopathy, we demonstrated that an increase in left ventricular end-diastolic volume, which is a measure of ventricular preload, is the main mechanism of adaptation that maintains the flow and stroke volume in the scenario of severe systolic dysfunction. The absolute systolic flow corrected for left ventricular end-diastolic volume in this study was representative of left ventricular global systolic function, whose usefulness and prognostic value should be studied in further research.