Microcalcifications and spotty calcification patterns within coronary plaques are associated with plaque vulnerability and increased risk of rupture, whereas dense, sheet-like calcification is characteristic of stable fibrocalcific lesions and correlates with reduced rupture risk.

Inflamed artery walls cause smooth muscle cells and other cells to turn into bone-like cells that release tiny sacs filled with calcium and phosphate. These sacs act as starting points for small, scattered calcium crystals to form inside the plaque. At the same time, an enzyme that normally blocks calcium buildup gets activated and removes this protection, letting more crystals grow. These small, irregular calcium deposits make the plaque fragile and prone to breaking open. In contrast, large, solid calcium sheets form slowly over time through different processes and make the plaque harder and more stable.