CmyoSize: An ImageJ macro for automated analysis of cardiomyocyte size in images of routine histology staining

•The macro CmyoSize measures the cardiomyocyte cross-sectional size in H&E images.•CmyoSize output include cross-sectional area and width of the cardiomyocytes.•CmyoSize results were comparable to measurements performed by an expert examiner.•CmyoSize analysis is at least 30-times faster than expert’s analysis.•CmyoSize runs within Fiji/ImageJ software and it is highly customizable. [Display omitted] Cardiomyocyte size histomorphometry is widely required in myocardial remodeling research, but it relies on subjective, time-consuming manual tracing. We aimed to present the CmyoSize, a Fiji/ImageJ macro that reproducibly measures the transnuclear cross-sectional size of cardiomyocytes in multiple H&E images. CmyoSize output per image are: mean cross-sectional area (CSA), CSA’s local standard deviation (LSD), mean width, and width’s LSD. CmyoSize was validated against measurements of an expert examiner, using myocardium micrographs (400-fold magnification) from rats treated with hyperbaric oxygen (HBO), streptozotocin (STZ), as well as control rats (five images/heart, five rats/group). CmyoSize achieved high cardiomyocyte detection precision (95.17 ± 1.11%) and it analyzed each image at least 30-times faster than expert examiner (8.44 ± 0.17 s vs. 266.70 ± 25.15 s). Bland-Altman analyses showed no meaningful bias ( ± 95% confidence interval) between both methods: mean CSA = 1.88 ± 6.83 µm2, CSA’s LSD = −4.55 ± 5.07 µm2; mean width = −0.02 ± 0.22 µm; width’s LSD = −0.16 ± 0.17 µm. Pearson’s r ranged from 0.85 to 0.94 (P