The majority of patients with Chagas disease (ChD) remain for 10 to 30 years or even for life in the indeterminate form (IF) of this disease. They have positive-specific serology tests for ChD, but no symptoms or physical signs, and normal findings for electrocardiograms (ECGs) and heart, esophagus, and colon radiographs. To investigate whether patients in this phase of disease have any impairment of left ventricular (LV) systolic performance, we assessed their contractility index by the slope of the LV end-systolic pressure-dimension (P(es)-D(es)) relation. We studied 35 patients with ChD (14 IF, 11 digestive form [DF], 10 cardiac form [CF]) and 13 healthy subjects. Patients with the CF had only minor cardiac involvement (bundle-branch block, normal LV ejection fraction). All patients had normal baseline global LV systolic function on 2-dimensional echocardiography, but minor segmental wall motion abnormalities were observed in 3 DF, 3 IF, and 2 CF patients. At rest and during intravenous phenylephrine infusion, we measured LV dimensions by echocardiography, and LV end-systolic pressure was estimated by a calibrated carotid pulse tracing. We also measured percent fractional shortening (%DeltaD) and the rate-corrected mean velocity of fiber shortening (Vcf(c)). Mean values (+/- SD) of %DeltaD and Vcf(c) were not significantly different from those exhibited by healthy control subjects in any of the ChD groups at rest (except for CF) or at peak stress using phenylephrine. The P(es)-D(es) slope was similarly and significantly reduced in all ChD patients (IF: 50.7 +/- 25; DF: 52.3 +/- 24; CF: 60.8 +/- 22 mm Hg/cm) compared with normal subjects (89 +/- 17 mm Hg/cm). The P(es)-D(es) slope was even more depressed (39.6 +/- 10 mm Hg/cm) in ChD patients who had minor segmental wall motion abnormalities (SWMAs) on the baseline 2-dimensional echocardiograph in comparison with the slightly reduced values found in patients with CF who had isolated conduction abnormalities on the ECG (71.8 +/- 10 mm Hg/cm). Although %DeltaD and Vcf(c), even at peak afterload, do not differentiate ChD patients from normal controls, the P(es)-D(es) slope is significantly impaired in IF, DF, and CF patients. The remarkably lower P(es)-D(es) slope value documented in ChD patients exhibiting only minor LVWMAs suggests a more extensive myocardial damage in this group of patients, indicating that they should be considered as exhibiting symptoms of the CF version of the disease.