Patogenia da cardiopatia chagásica crônica / Pathogeny chagasic cardiopathy

Recentemente, o interesse pelo estudo da patogenia da doença de Chagas foi estimulado pela possibilidade de utilizaçäo do transplante cardíaco na doença de Chagas, pela incidência da síndrome de imunodeficiência adquirida em portadores da doença, por resultados de investigaçäo que tem procurado detectar o parasita ou parte dele nas lesöes crônicas da miocardiopatia chagásica, por anormalidades vasculares no coraçäo demonstradas em portadores de doença de Chagas e pelo potencial uso de drogas na aprevençäo do seu densevolvimento. Inúmeras teorias têm sido propostas para explicar a patogenia da doença desde que Carlos Chagas incicialmente a descreveu. No entanto, nenhuma delas tem sido convincente o suficiente para ser aceita pela maioria dos pesquisadores e médicos que se defrontam com esta doença. Diferentes mecanismos têm sido proprostos para a patogenia da doença de Chagas na forma crônica com diferentes implicaçöes terapêuticas. Os principais säo: a presença do parasita determinando o processo inflamatório, processo alérgico, mecanismo auto-imune, processo secundário à disfunçäo do sistema nervoso autonômico e o envolvimento microvascular.

Holter monitoring in Chagas' heart disease

Electrocardiographic rythm disturbance evaluation by Holter monitoring is increasingly becoming a useful methodologic tool for risk stratification as well as for therapeutic assessment in patients with Chagas' disease. Furthermore, late potential analyses, now being directly obtained from Holter recording has promising perspectives in enhancing identification of patients with high risk profiles for development of malignant ventricular arrhythmias. In addition, recently incorporated to Holter studies, heart rate variability analysis will certainly contribute to a better understanding of the characteristic autonomic nervous system disarray that commonly affects chagasic patients.

Signal-averaged electrocardiogram in chronic Chagas' heart disease

The aim of the study was to register the prevalence of late potentials (LP) in patients with chronic Chagas' heart disease (CCD) and the relationship with sustained ventricular tachycardia (SVT). 192 patients (96 males), mean age 42.9 years, with CCD were studied through a Signal Averaged ECG using time domain analysis. According to presence or absence of bundle branch block (BBB) and SVT, four groups of patients were created: Group I (n = 72): without SVT (VT-) and without BBB (BBB-): Group II (n = 27): with SVT (VT+) and BBB-; Group Ill (n = 63): VT- and with BBB (BBB+); and Group IV (N = 30): VT+ and BBB+. The LP was admitted, with 40 Hz filter, in the groups without BBB using standard criteria of the method. In the group with BBB, the root-mean-square amplitude of the last 40 ms (RMS) < = 14 microV was considered as an indicator of LP. Results: In groups I and II, LP was present in 21 (78 percent) of the patients with SVT and in 22 (31 percent) of the patients without SVT (p < 0.001), with Sensitivity (S) 78 percent; Specificity (SP) 70 percent and Accuracy (Ac) 72 percent. LP was present in 30 (48 percent) of the patients without and 20 (67 percent) of the patients with SVT, in groups Ill and IV. p = 0.066, with S = 66 percent; SP = 52 percent; and Ac = 57 percent. In the follow-up, there were 4 deaths unrelated to arrhythmic events, all of them did not have LP. Eight (29,6 percent) of the patients from group II and 4 (13 percent) from group IV presented recurrence of SVT and 91,6 percent of these patients had LP. Conclusions: LP occurred in 77.7 percent of the patients with SVT and without BBB. In the groups with BBB, there was association of LP with SVT in 66,6 percent of the cases. The recurrence of SVT was present in 21 percent of the cases from which 91,6 percent had LP.

O eletrocardiograma de longa duraçäo (Holter) na doença de Chagas / Holter monitoring in Chagas'disease

A utiliazaçäo do método de Holter na doença de Chagas tem permitido melhor conhecimento das suas anormalidades elétricas e do comportamento das alteraçöes eletrocardiográficas transitórias, colaborando no estabelecimento do grau de risco e no controle de procedimentos terapêuticos. a introduçäo de nvoas tecnologias ao método, como a análise da variabilidade da frequência cardíaca com possibilidade de avaliar a atividade autonômica sobre o nó sinusal, poderá permitir avaliaçäo näo-invasiva desse aspecto täoimportante da doença. A possibilidade da aquisiçäo do eletrocardiograma de alta resoluçäo a partir de gravaçöes de Holter poderá ampliar a avaliaçào do risco desses pacientes.

Abordagem do idoso assintomático com arritmia / Approach to the asymptomatic elder with arrhythmias

A prevalência de arritmias cardíacas aumenta com o envelhecimento. Em pacientes idosos, a necessidade da identificaçäo de doenças näo cardíacas e o uso de drogas que favoreçam a ocorrência de arritmias, säo particularmente importantes. O significado clínico das arritmias varia em funçäo da presença de isquemia miocárdica e de disfunçäo ventricular. As decisöes terapêuticas devem fundamentar-se na condiçäo clínica geral do pacientes, evitando examinar a arritmia de modo isolado