Accumulation of activated mast cells in the shoulder region of human coronary atheroma, the predilection site of atheromatous rupture.

The far higher proportion (50-fold) of activated mast cells in the shoulder region of atheromas supports the hypothesis that mast cells, a cell type capable of triggering matrix degradation, actively participate in the destabilization and ensuing rupture of coronary atheromas and thus may trigger an acute coronary event.