Noninvasive diagnosis of cardiac rejection through echocardiographic tissue characterization

Ultrasonic tissue characterization is based on the assumption that microscopic tissue structures are identifiable by their acoustic properties. Our study group consisted of 23 cardiac recipients. Two-dimensional images were obtained within 2 hours of endomyocardial biopsy. The end-diastolic echo frames were digitized into the matrix of an image-processing system. A region of interest was placed into the anteroseptal segment of the left ventricle. The texture within the region of interest was analyzed using four major groups of texture analysis (first-order histogram, co-occurrence matrix, run-length statistic, and power spectrum). A total of 408 echocardiographic examinations were compared with histologic findings. The 117 initially calculated texture parameters were reduced incrementally using a series of discriminant analyses. A set of three texture parameters (inverse difference moment undirected, run-length nonuniformity vertical, and sector sum) was able to describe changed echocardiographic texture when rejection occurred. Using these three parameters, echocardiographic sensitivity was 89.0% and specificity was 83.6% for moderate rejection. We conclude that cardiac rejection is associated with echocardiographic texture alterations and that serial echocardiographic texture analysis can reliably identify rejection.