Vacuolated cardiomyocytes in human endomyocardial biopsy specimens

We encountered an unfamiliar finding during electron microscopic examination of an endomyocardial biopsy obtained from a 55-year-old woman suffering from heart failure due to dilated phase hypertrophic cardiomyopathy. Many cardiomyocytes contained large vacuoles that were mainly empty except for small amounts of amorphous substrate. These were not autophagic vacuoles, as they lacked limiting membranes. Six years later, we encountered similar histological findings in three successive biopsies sourced from another hospital. They were obtained from a 77-year-old man with hypertrophic cardiomyopathy, a 28-year-old woman with endocardial fibrosis, and a 33-year-old man with dilated cardiomyopathy. This biopsy was the second for the endocardial fibrosis patient, and her first biopsy showed no vacuoles within cardiomyocytes. Close inspection of the procedures revealed that in all of these cases the fixed biopsy specimens were carried to the hospital from other institutes using a refrigerated courier service. We then fixed rat heart tissues, froze them once, and processed them for electron microscopy. In that experiment, we were able to reproduce the vacuolar cardiomyocytes, thereby demonstrating it to be a laboratory artifact. We therefore want to emphasize to physicians not to freeze biopsy specimens and not to use a refrigerated courier service for their transport. <Learning objective: Under an electron microscope, large vacuoles were observed within many cardiomyocytes in endomyocardial biopsies obtained from 4 patients with cardiomyopathies of different etiologies, which were not autophagic vacuoles. Since an animal experiment could reproduce a similar histological finding by freezing the tissue after fixation, such an unfamiliar finding was considered to be a laboratory artifact. We would call physicians' attention not to freeze the biopsy specimens even after fixation.>.