Histological findings
We compared histological findings in patients with TCM with findings in patients who had ICM or DCM. We found distinct differences in the presence of T cells, which were strongly associated with ICM (0.2 cells in high power field (HPF) in TCM vs. 1.1 cells in HPF in ICM vs. 0.27 cells in HPF in DCM; overall p < 0.0001) (Figure 2A). The presence of CD 68 positive macrophages was not significantly more frequent in patients with TCM compared with DCM, but less frequent compared with patients with ICM (0.45 cells in HPF in TCM vs. 0.47 cells in HPF in DCM vs. 1.1 cells in HPF in ICM; overall p < 0.0001) (Figure 2B).
Figure 2: Comparison of Biopsies.
(A) CD3+ T cells and (B) CD68+macrophages as well as (C) immunohistological score of myocardial fibrosis (trichrome staining), and (D) anti–cleaved caspase 3 are compared in myocardial biopsy samples from patients with tachycardia-induced cardiomyopathy (TCM), inflammatory cardiomyopathy (ICM), and dilated cardiomyopathy (DCM).
***: p-value < 0.001 compared to TCM; ns: not significant compared to TCM
In patients with TCM, MHC-II (anti–major histocompatibility complex class II) expression was similar to that in patients with ICM and significantly enhanced compared with DCM (38.9 % in TCM vs. 54.4% in ICM vs. 4.1% in DCM; overall p < 0.0001) (Figure 3).
Figure 3: MHC-II (anti–major histocompatibility complex class II) expression
TCM: tachycardia-induced cardiomyopathy; ICM: inflammatory cardiomyopathy; DCM: dilated cardiomyopathy; ***: p-value < 0.001 compared to TCM
Patients with TCM had a moderately increased degree of fibrosis which was slightly higher in patients with DCM and ICM (fibrosis score [0 to 4]: 1.6 in TCM vs. 2.1 in ICM vs. 1.9 in DCM; severe fibrosis: 6.7 % in TCM vs. 8.9 % in ICM vs. 17.6 % in DCM; overall p=0.45) (Figure 2C).
Apoptosis and cell death are essential issues in HF. The presence of cleaved caspase 3, a specific indicator for apoptosis, was lowest in the DCM (48 % cells in HPF in TCM vs. 50 % cells in HPF in ICM vs. 42 % cells in HPF in DCM; overall p < 0.0001). Notably, despite the excellent recovery potential of TCM, the marker of apoptosis in patients with TCM was elevated o a similar degree compared to those with ICM (Figure 2D).