Morphometrical and stereological analysis of myocardial mast cells in myocarditis and dilated cardiomyopathy.

Mast cells play a certain role in inflammation and immunological reactions. Cardiac mast cells, shown by sodium sulfate-alcian blue staining, were evaluated in endomyocardial biopsy specimens in patients with unexplained congestive heart failure. The results of histopathological analysis were consistent with active myocarditis according to the Dallas criteria in 10 patients (15%), borderline myocarditis in 9 (13.8%), and dilated cardiomyopathy in 25 patients (38.5%); these results were compared with a control group of 10 traffic accident victims. The highest numerical areal density of mast cells was found in active myocarditis (3.92 counts/mm2, SD = 1.84), followed by borderline myocarditis (2.76 counts/mm2, SD = 1.66), dilated cardiomyopathy (1.56 counts/mm2, SD = 0.45) and control group (0.77 counts/mm2, SD = 0.19). Degranulation involved 27% (SD = 3.6) of mast cells in active myocarditis, 18% (SD = 4.5) of mast cells in borderline myocarditis, 10.8% (SD = 3.12) of mast cells in dilated cardiomyopathy and 4% (SD = 2.0) of mast cells from autopsy tissue. The differences among the four groups were statistically significant (P <0.001). The increased number of mast cells and the higher degree of their degranulation in myocarditis compared to dilated cardiomyopathy and to control group indicate that they were activated. The mast cells could be involved in modulation of fibrous response, since they tended to be associated with areas of fibrosis. Likewise, numerical areal density and degree of degranulation of mast cells could also be used as additional diagnostic criteria for acute myocarditis, since a higher numerical areal density and degree of degranulation were present in myocarditis vs. dilated cardiomyopathy and control group.