High-density lipoprotein (HDL), also known as "good cholesterol", can help prevent narrowing or clogged arteries by removing bad cholesterol. However, Cleveland Clinic researchers have found that some enzymes in the blood can make HDL dysfunctional and increase the risk of plaque buildup and heart problems. Learn how Cleveland Clinic is hoping to develop a blood test to measure the level of dysfunctional HDL to better estimate a person's risk for heart disease.