Subacute Chagas' Disease

Several investigators (Laranja, Oliveira, and Andrade) have described a subacute cardiac form of Chagas' disease. This is seen rarely in young patients and is characterized by severe rapid heart failure. These patients fail to respond to the usual therapeutic modalities and do not have fever or other signs of acute Chagas' disease. Large numbers of parasites are present in the cardiac fibers and perhaps in the peripheral blood as well. Microscopically, there is an intense diffuse myocarditis with exudative changes, marked interstitial inflammation, and often degenerative changes in the cardiac fibers, at times with the Magarinos-Torres' lesion.

Latent (Indeterminate) Chagas' Disease

The acute stage of Chagas' disease usually resolves completely in a few weeks or months, but may pass into a latent subacute or chronic stage. Patients who recover from the acute disease, as well as millions of people in endemic areas who have never had clinical evidence of Chagas' disease, have a positive complement fixation test (Machado-Guerreiro reaction). Others have a positive xeno text. Since spontaneous cures have not been seen in patients with T. cruzi infection, the assumption has been made that in the latent phase a patient may harbor the infection without symptoms and with a normal physical examination, ECG, chest radiograph, barium swallow, and barium enema, but a positive serum or blood test. It is unknown whether these patients have a host-parasite equilibrium without developing additional lesions or whether, in fact, they have slowly progressive lesions.

This latent stage has also been called "indeterminate or undetermined phase" and 2% to 5% of these patients become symptomatic each year so that, between 10 and 20 years, about 4% of this group will become symptomatic, with the figure rising to 70% in 40 years. Reactivation may occur when HIV-positive patients develop AIDS.

In one follow-up study of 72 patients with acute disease over a 4-10 year period, 15% had ECG changes indicating an active myocarditis. Diminution in the number of ganglion cells in the Auerbach plexi of the digestive tract is occasionally found in patients with a positive complement fixation test, who are ill or dying of causes other than trypanosomiasis. In patients with the "latent" phase of Chagas' disease, changes in esophageal motility have been diagnosed by barium swallow studies or by placing a balloon within the esophagus and recording peristaltic activity. Thus, a person with a positive complement fixation test or positive xenodiagnosis probably should not be placed in the latent category unless the ECGs are normal and function of the alimentary tract is also found to be normal.

More recently, echocardiograms of this group have shown a high incidence of ventricular wall dyskinesis and hypokinesis, mainly in the apical region, which helps to differentiate this myocardiopathy from others. Minor cardiac involvement may be seen, with dilatation of the heart but normal motility; the systolic volume is increased but ventricular function is preserved. Alteration of myocardial contraction may be noted with the use of isoproterenol and isotonic effort maneuvers. The future will probably show if these patients will become symptomatic in a shorter period of time and if they will have a poorer prognosis.