Researchers have found a genetic variant that doubles the likelihood that people will have calcium deposits on their aortic valve. Such calcification, if it becomes severe, can cause narrowing or a blockage of the aortic valve, a condition called aortic stenosis. The study is the first large-scale, genome-wide association study to uncover a genetic link to aortic valve calcification. An article detailing the findings is published in the February 7, 2013 issue of The New England Journal of Medicine.
The study's lead investigators — from Johns Hopkins, Harvard University, McGill University, the University of Iceland and the National Institutes of Health — found that having a genetic variant in the LPA gene, which codes for a type of cholesterol particle called lipoprotein (a), also increases the risk of developing aortic stenosis by more than 50 percent.
The researchers say their findings not only help explain why heart valve calcification may run in families, they could also lead to the development of targeted medications that might slow the progression of the disease. Statin medications, which reduce common forms of cholesterol that can clog blood vessels, have not been shown to reduce aortic valve calcification.
"This is an important step forward in understanding the biology of the development of aortic stenosis and how this common genetic variant, which is found in 7 percent of the general population, contributes to that risk," says Wendy Post, M.D., a cardiologist and associate professor of medicine and epidemiology at the Johns Hopkins University School of Medicine who is a senior author of the study.
Non-genetic risk factors for aortic valve calcification include advancing age, high blood pressure, obesity, high cholesterol levels and smoking. Men are at higher risk than women.
In the study, the researchers first looked at 2.5 million gene variants, called single nucleotide polymorphisms or SNPs, among more than 6,900 people of white European background, and found that this variant in the LPA gene was strongly associated with having aortic valve calcification on a heart CT scan, according to lead author Catherine Campbell, M.D., formerly the chief cardiology fellow at Johns Hopkins who now works for Kaiser Permanente.
Lipoprotein (a) is an unusual type of cholesterol particle that circulates in the blood and is associated with an increased risk for heart attacks.
"Increased levels of lipoprotein (a) have been previously associated with aortic valve disease. However, prior studies could not differentiate whether it was simply a marker or a causal factor," says Campbell. "Our results provide the first evidence for a causal relationship between lipoprotein (a) and calcific aortic valve disease," she adds.