Quantitative Changes in Mast Cell Populations After Left Ventricular Assist Device Implantation

Background: Mast cells have been implicated as important in tissue remodeling and fibrotic increases. We investigated the effect of chronic ventricular unloading on myocardial fibrosis and cardiac mast cell density in patients undergoing left ventricular assist device (LVAD) implantation. Methods: Myocardial tissue was obtained from samples of 30 patients with end-stage cardiomyopathy at the time of left ventricular assist device implantation and removal and from donor hearts. Tissue sections were stained and quantitated for mast cells and myocardial fibrosis. Results: Mast cell density in cardiomyopathy (33.5 ± 3.6 SEM cells/10 fields) was higher than that in donor hearts (15.25 ±2.0 SEM cells/10 fields p=0.04) and was lower than LVAD supported hearts (49.8±5.7 SEM cells/10 fields p=0.01). Mast cells were primarily localized in areas of increased interstitial fibrosis adjacent to myocardial cells and not vessels. There was statistically significant correlation between mast cells and collagen (p = 0.03) in patients before LVAD implantation that did not persist after mechanical support (p = 0.18). Conclusion: These results suggest that chronic support with left ventricular assist devices induces an increase in mast cell number in the myocardium. The increase in mast cell density may not correlate to its role in the fibrotic cascade since after LVAD implantation there is no significant relation between mast cell density and collagen amount.