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Nonobstructive coronary artery disease (CAD) can increase risk of death or heart attack significantly, a new study reported. The researchers found that the risk spiked within one-year post diagnosis.

According to the press release, nonobstructive CAD is characterized by "atherosclerotic plaque that would not be expected to obstruct blood flow or result in anginal symptoms." However, there have been studies that questioned the potential health dangers of nonobstructive CAD.

For this study, the researchers examined the medical data on nearly 38,000 U.S. veterans who underwent elective coronary angiography to look for signs of CAD.The team compared the heart attack and death rates in patients with nonobstructive CAD, obstructive CAD and no apparent CAD. The data were collected between October 2007 and September 2012.

Overall, the researchers found that 22.3 percent had nonobstructive CAD and 55.4 percent had obstructive CAD. Within a year post diagnosis, 845 patients had died whereas 385 required rehospitalization for myocardial infarctions, also known as a heart attack. The team reported that risk of death and heart attacks increased depending on the extent of the CAD, which meant that patients with nonobstructive CAD were not safe. In fact, when the researchers compared these patients' risk of MI to patients with no apparent CAD, they found that the risk increased by two to 4.5 times.

"These findings highlight a need to recognize that nonobstructive CAD is associated with significantly increased risk for MI, consistent with prior biologic studies indicating that a majority of MIs are related to nonobstructive stenosis [narrowing of an artery]. Correspondingly, these results reveal the limitations of a dichotomous [divided into two parts] characterization of angiographic CAD into 'obstructive' and 'nonobstructive' to predict MI and highlight the importance of preventive strategies such as pharmacotherapy treatments and lifestyle modifications to mitigate these risks," the authors concluded.

The study was published in JAMA.