RESUMEN
Intraoperative biopsy specimens were used to analyze the sizes and ultrastructure of cardiomyocytes (CMC) in the atrialized right ventricle (ARV) versus those in the right ventricle (RV) and right atrium (RA) in 32 patients aged 9 months to 57 years with Ebstein anomaly. The mean CMC diameter in ARV, RV, and RA did not differ significantly in patients less than 10 years; that was equal in ARV and RV, but higher in RA in patients over 10 years of age. No specific atrial granules were found in the CMC of ARV, RV, and RA; but T system channels and multiple intercalated disks were encountered significantly more frequently than in the RA cells. Individual CMCs showed abnormal myofibrils with specific accumulations of Z-band material (more commonly in RA), as well as nuclear displacement under the sarcolemma (more commonly in ARV and RV). Conclusion. ARV cardiomyocytes preserve ventricular specificity in patients with Ebstein anomaly.