Computer-assisted quantitation of myocardial fibrosis in histologic sections

Histologic characterization of the myocardium may require estimation of the collagen content of the specimen. A computer-assisted method can be used to determine collagen content from histologic sections. Full-thickness segments of normal or fibrotic left ventricular myocardium from ten human hearts were divided into portions for hydroxyproline assay and for trichrome staining of histologic sections. The sections were digitized using a computerized video analysis system and were segmented into collagen and muscle regions using a gray-level threshold technique that yielded an estimate of the percent of collagen. A wide range of collagen content, from normal (5 micrograms of hydroxyproline per milligram of dry weight) to fibrotic (38 micrograms/mg) myocardium, was studied. The percentage of collagen from analysis of histologic sections strongly correlated with the hydroxyproline level, with excellent intraobserver and interobserver concordance. Results were unaffected by variations in histochemical staining.