The majority of patients with Chagas' disease remain for 10 to 30 years in the indeterminate form (IF) of this disease. They have no symptoms, serologic positivity, normal electrocardiogram results and heart size, and normal left ventricular global and segmental systolic function on 2-dimensional echocardiography. To investigate whether this group of patients have any impairment of left ventricular global performance (Tei index) and diastolic function, we have studied 43 individuals (age 49 +/- 12 years) including 14 healthy volunteers and 29 patients with Chagas' disease divided as IF (n = 12) and cardiac form (n = 17). Echocardiographic measurements included ejection fraction, Tei index, left atrial volume index, transmitral (peak early transmitral flow velocity, late peak mitral velocity, tissue Doppler, late peak mitral velocity duration) and pulmonary (systolic pulmonary vein velocity, diastolic pulmonary vein velocity, retrograde pulmonary vein velocity, retrograde pulmonary vein velocity duration) flow velocities, and tissue Doppler velocities at lateral mitral annulus (peak early transmitral flow velocity, late peak mitral velocity, systolic pulmonary vein velocity). Although ejection fraction and S' velocity were significantly lower for patients with cardiac form compared with control and IF groups, Tei index was not able to differentiate patients with cardiac conditions from the other groups. Diastolic dysfunction was documented for patients with cardiac form by left atrial volume index, early transmitral peak velocity, early expansion wave by tissue Doppler, late expansion wave by tissue Doppler, and peak early transmitral flow velocity/early expansion wave by tissue Doppler. Patients with the IF of Chagas' disease did not show any abnormality of diastolic function. Thus, when the IF is further characterized on the basis of absence of any echocardiographic marker of regional systolic dysfunction, no impairment of diastolic function can be detected.