RESUMO
AIM: to investigate changes in the diameter and length of hypertrophic cardiomyocytes (CMCs) in the dilated left ventricle (LV). SUBJECTS AND METHODS: Light microscopy, morphometry, and statistical analysis were used to investigate the status of the contractile apparatus and changes in the length, diameter of CHC and diameter of CMC nuclei, by using intraoperative dilated LV biopsy samples from 31 patients with valvular disorders and dilated cardiomyopathy. Morphological findings were compared with the clinical parameters of the patients. RESULTS: CMCs in the patients with the dilated LV were hypertrophic and were at different stages of restructuring with progressive myofibrillar loss (PML). In 81% of patients, the diameter of CMCs was not significantly changed as their zones of PML extended. The length of CMCs, which correlated with the enlarged LV cavity, was increased in 52% of patients during cell restructuring with PML. In 42% of patients, the CMC nuclear diameter increased during restructuring with PML, which appeared to be associated with CMC polyploidization; in some of these patients (19% of the total number of patients), the diameter of CMCs increased in parallel with the higher diameter of their nuclei. CONCLUSION: The findings suggest that after completion of their transverse growth, hypertrophic CMCs are involved in a restructuring process with PML. The findings are consistent with the hypothesis that dilatation of the hypertrophied LV cavity is related to the preferential elongation of CMCs with an inadequate increase in their diameter. The results of the investigation may assume that the higher CMC diameter that brings to completion before the entry of the cells into the restructuring process with PML, resumes in the cells, the ploidy of which increases in the course of restructuring with PML, triggering an additional mechanism for raising the CMC diameter at this stage of myocardial hypertrophy. The results are indicative of different mechanisms for increasing the diameter and length of hypertrophic CMCs, since the diameter of CMCs directly correlates with that of their nuclei, and the length increases as the zones of PML extend in the CMCs.