Non-obstructive coronary artery disease was associated with a 28 to 44 percent increased risk of a major adverse cardiac event such as a heart attack or death, in a new study presented at the American Heart Association's Quality of Care and Outcomes Research 2014 Scientific Sessions.

Non-obstructive CAD damages the walls of the heart's blood vessels, but doesn't result in decreased blood flow or symptoms so it's generally been considered to be a low-risk condition.

In this study, researchers studied 40,872 veterans who underwent elective cardiac angiography from October 2007 to September 2012. The patients' condition was categorized as normal, non-obstructive and obstructive CAD. The rates of heart attack and death within one year following angiography increased progressively with increasing CAD severity, even among those patients with non-obstructive CAD, researchers found.

"Unlike obstructive CAD, which blocks blood flow, non-obstructive CAD may initially appear less threatening on angiography tests since it doesn't result in decreased , but it appears to have significant risk for and death" said Thomas M. Maddox, M.D., M.Sc., the study's lead researcher, a cardiologist for the VA Eastern Colorado Health Care System and associate professor of medicine at the University of Colorado School of Medicine in Denver. "Dismissing non-obstructive CAD as harmless could be dangerous. Our findings show there is indeed a risk, that non-obstructive damage can lead to heart attacks just like obstructive disease, and that we should consider preventive therapies for these patients."

Patients with non-obstructive disease should ask their physicians about preventative therapies, like quitting smoking, healthy diets, getting enough exercise, losing weight and taking preventative medications such as aspirin and statins.