These plaques harden and constrict the arteries, decreasing blood flow and oxygen supply to key organs and raising the risk of blood clots, which could block blood flow to the heart or brain. Atherosclerosis usually has no symptoms at first, and many people are unaware they have it, but if it progresses, it can lead to life-threatening complications such as heart attacks and strokes. However, a healthy lifestyle can help avoid the illness, and therapy can help lower the chance of major complications. Atherosclerosis is associated with a variety of health problems. Atherosclerosis can develop to a variety of dangerous illnesses known as cardiovascular disease if left untreated (CVD). Until CVD manifests itself, there are usually no symptoms.