Correlação clínico-patológica na forma indeterminada da doença de Chagas experimental do cão / Clinico-Pathological Correlation in the Indeterminate Form of Experimental Chagas' Disease in Dogs

PURPOSE: To study the functional cardiac component of the indeterminate form of experimental Chagas' disease in dogs. METHODS: Four dogs chronically infected with Trypanosoma cruzi and eight normal controls were used. They were submitted to several invasive procedures, either in the presence of complete autonomic block or not, to test for disturbances in the origin and conduction of electric stimuli and the function of cardiac muscle. Histological examination of the heart and its conduction systems was performed in all animals. RESULTS: Mild to moderate focal myocarditis was found in infected dogs, often involving the conduction system of the heart. Sections of the heart from control dogs were histologically normal. Functional data on excitability, intra and interatrial conduction time and sinus node recovering time were essentially similar for both infected and control animals. CONCLUSION: Focal myocarditis, the hallmark of the indeterminate form of Chagas' disease, did not alter the normal parameters of cardiac function, as seen after investigation with sensitive invasive techniques. It is probable that subjects considered as belonging to the indeterminate form of Chagas' disease, but presenting mild alterations at sensitive exploratory tests, may have more severe lesions than that usually described or may be already in the early progressive cardiac form of the disease.

Síndrome de pré-excitaçäo por fibras nodofasciculares (Mahaim): relato de dois casos / Pre-excitement syndrome by nodofascicular (Mahaim)fibers: report of 2 cases

A participaçäo de vias anômalas nodofasciculares ou de Mahaim no circulo de taquicardia clínica ou entäo no aspecto do eletrocardiograma (ECG) basal é descrita, respectivamente, em 2 pacientes. No caso 1, com crises recorrentes de taquicardia paroxística, o ECG basal näo mostrava qualquer forma de pré-excitaçäo e o QRS era normal. Durante a taquicardia, o QRS apresentava aspecto de bloqueio completo do ramo esquerdo (BCRE) e a freqüência cardíaca era de 180 bpm. Durante o estudo eletrofisiológico, demonstrou-se a presença de dupla via nodal, estando o início da taquicardia clínica na dependência de bloqueio da via rápida e conduçäo pela via lenta, induzido por extra-estímulos atriais. A transiçäo de conduçäo para a via lenta coincide com o encurtamento do intervalo HV e com o aparecimento de morfologia de BCRE. Quando se atinge intervalo crítico de alongamento da conduçäo pela via lenta nodal, a taquicardia clínica é disparada. Os componentes anterógrado (via lenta nodal - via nodofascicular) e retrógrado (porçäo proximal do ramo direto - tronco do feixe de His - via nodal rápida) podem ser estudados e a açäo benéfica do verapamil demonstrada. No caso 2, o paciente näo tinha taquicardia e o ECG basal mostrava sinusal intervalo PR = 0,18 e QRS com morfologia de BCRE. A presença de vias nodofasculares no determinismo da imagem de BCRE demonstrada pela presença de intervalo HV = 0 e pela normalizaçäo do QRS com estimulaçäo do feixe de His