Ultrasonic tissue characterization for patients with Chagas' disease

Abstract

This study was undertaken to test the hypothesis that ultrasonic tissue characterization, as evaluated by intensity and cardiac cyclic variation of integrated backscatter (IBS), could identify early myocardial involvement in Chagas' disease. We evaluated 69 participants, age 15 to 73 years (mean ± SD: 49 ± 12 years), who were divided as following: 19 control subjects; 13 patients with the indeterminate form of Chagas' disease; 7 patients with the digestive form; and 30 patients with the cardiac form. IBS images were obtained in parasternal short-axis (basal, papillary muscle, apical) view and analyzed in 12 left ventricular (LV) segments (anterior, lateral, posterior, and septal). The following IBS variables were evaluated: (1) the corrected coefficient (CC) of IBS, obtained by dividing IBS intensity, in each cardiac segment, by IBS intensity measured in a rubber phantom using the same equipment adjustments at the same depth; and (2) magnitude of cardiac cyclic variation (MCV) of IBS, as measured by the peak-to-peak difference between maximal and minimal values of IBS in cardiac cycle. The CC of IBS was increased ( P < .05) for patients with the cardiac form who had LV segments with normal wall motion as compared with control subjects, in 4 of 12 segments evaluated (basal anterior, midposterior and midseptal, anterior apical), whereas the remaining chagasic groups were comparable with controls subjects. The CC of IBS tended to increase with worsening of LV segmental wall motion. MCV showed a large individual variability and had a large mean value ( P < .05) in just 1 of 12 segments evaluated, when patients with the cardiac form were compared with control subjects. No correlation was observed between the magnitude of LV dysfunction and MCV of IBS. In conclusion: (1) the CC of IBS was able to provide early differentiation of cardiac involvement for patients with Chagas' disease who had LV segments with normal wall motion; (2) increase of CC of IBS with worsening of LV segmental wall motion suggests a relationship between the acoustic properties of myocardial tissue and grading of myocardial fibrosis; (3) MCV was not able to differentiate patients with Chagas' disease from control subjects; and (4) patients with the indeterminate form of Chagas' disease were not differentiated from control subjects by any of the IBS techniques evaluated in this study.