This is good information to have:

The different types of heart plaques
Coronary plaques are classified into three different categories: calcified, non-calcified, and low-density non-calcified plaques.
Low-density non-calcified plaques, also referred to as high-risk or soft plaques, are made up of fat and connective (fibrous) tissue and are often the most dangerous.
Non-calcified plaques contain fibrous tissues and have some risk to the patient, but not as much as low-density non-calcified plaques.2
Calcified plaques are composed mostly of calcium and are the least likely to cause a plaque rupture or heart attack.
Low-density non-calcified plaques are the most dangerous plaques due to their higher likelihood to rupture. When a plaque ruptures, it can cause a blood clot. This blood clot blocks blood flow to the heart muscle and causes chest pain, a heart attack, or death in some cases.
Non-calcified plaques are not as prone to rupture as low-density plaques but can still cause a rupture or blockage in the arteries if left untreated. Calcified plaques are the least likely to cause a rupture or blockage as they are more stable than non-calcified and low-density non-calcified plaques.