Estudo da Troponina I cardíaca como marcador bioquímico de lesãomiocárdica isquêmica em fetos de gestantes aloimunizadas pelo fator Rh

Abstract

Introduction: The maternal alloimmunization is the main cause of fetal anemia in Brazil and also an important cause of preventable perinatal mortality. The severely anemic fetuses need intrauterine transfusions when developing the compensation mechanisms to improve their perinatal prognostic. Goal: Identify the presence of cardiac Troponin I on the blood of the fetuses umbilical cord whose mothers werealloimmunizated by the Rh factor, as a biochemical marker of fetal myocardial ischemia. Patients and methods: Its a prospective transversal study where 65 supposedly anemic fetuses from 64 alloimmunizated pregnant women were observed on the Fetal Medicine Center of the Hospital das Clinicas of the Universidade Federal de Minas Gerais, on the period from 2001 to July of 2008. The realization of the invasive procedure for propaedeutic or therapeutics was indicatedwhen necessary, according to the service protocol. Each procedure was considered a separate case. 39 fetuses from 38 alloimmunzated pregnant women were selected and submitted to cordocentesis procedures, totaling 54 cases, from which 27 are cases of fetuses who are known to be anemic and 27 are cases of non anemic fetuses. As to age and parity, was observed a greater occurrence on pregnantwomen with age between 30 and 35 years and parity 2 and 3 in the moment of the inclusion in the study. The antibody anti D was observed in 97,4% of the cases and appeared in isolated form in 44,7%. In 86.8% of the cases, a lack of postnatal prophylactic immunoglobulin use was the probable cause of alloimmunization. The average gestational age (in weeks) presented on admission of 28,2 weeks varying between 22 and 34 weeks. To determinate immediately the hemoglobin levels, thecordocentesis was done by means of HEMOCUE, one sample of fetus blood was centrifuged and the obtained plasma was frozen for posterior determination of cardiac Troponin I levels by means of the VIDAS® Troponin I Ultra (TNIN) test. The qualitative variables were analyzed using the frequency tables, the quantitative variables were described by the central tendency measures, the measures of dispersion (standard deviation, minimum, maximum) from graphics, histograms andbox plots. The Pearson's chi-square asymptotic test was utilized for the comparison between anemic and non-anemic fetuses. The exact test was utilized for the qualitative variables. Results: As for the Déf Hb the non-anemic fetuses showed a variation of -5,11 g/dl a 1,79 g/dL, characterizing lack of anemia. On the anemic fetuses only one presents moderate anemia with Déf Hb of 5,47 g/dL (5 g/dl Déf Hb 7 g/dL) all the remained fetuses showed Déf Hb > 7g/dL characterizing severeanemia. At the value of initial Coombs Indireto it was observed that 92,6% of the anemic fetuses showed an entitling of 1:256. Considering the anemic fetuses, the hydropsy was present when the shortage of Hb was higher that 7g/dl, difference statistically significant by the means of the the Pearson's chi-square test with p<0,0001. The cardiac Troponin I dosage was <0,01 g/L for both anemic and nonanemic fetuses Conclusion: The cardiac Troponin I wasnt identified on fetusesumbilical cords whose mothers were alloimmunizated by the Rh factor, suggesting that theres no ischemic myocardic lesions on these fetuses.