Patients with nonobstructive CAD still at risk for MI, death

Coronary artery disease (CAD) may not have to be obstructive to increase patients’ risks for MI or all-cause mortality. According to a study published online Nov. 4 in JAMA, patients diagnosed with nonobstructive CAD through coronary angiography were two times more likely to experience MI within one year of diagnosis as those with no apparent CAD.

Thomas M. Maddox, MD, MSc, of the division of cardiology at the Denver Veterans Affairs Medical Center, and colleagues found that instead of an abrupt shift in risk between nonobstructive and obstructive CAD, the magnitude of risk increased the more diseased vessels there were on a continuum through obstructive CAD.

Using the VA Clinical Assessment, Reporting and Tracking program, Maddox et al retrospectively captured longitudinal data on patients undergoing elective coronary angiography between 2007 and 2012. CAD levels were defined by degree and distribution of stenoses, ultimately creating seven cohorts, including nonobstructive CAD or obstructive CAD with one-, two-, or three-vessel involvement or no apparent CAD. The research team was able to follow these patients through one year post-index angiography. Patients with prior CAD diagnosis were excluded.

They found that the incidence of one-year MI was lowest in patients with no apparent CAD (0.11 percent), but increased through the levels of nonobstructive and obstructive CAD. One-year MI rates in one-, two- and three-vessel nonobstructive CAD were 0.24 percent, 0.56 percent and 0.59 percent, respectively. Obstructive CAD MI rates were 1.18 percent, 2.18 percent, and 2.47 percent for one-, two- and three-vessel involvement, respectively, at one year.

Mortality rates ranged from 1.38 percent in patients with no apparent CAD to 4.3 percent among obstructive CAD patients with the most vessel involvement.

Risk for MI in patients with nonobstructive CAD ranged between two and four-and-a-half times that of patients with no apparent CAD, and remained at an increased risk for death and other adverse outcomes.

Maddox et al wrote, “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 stenoses.” They suggested that current characterization downplays risks and is potentially more harmful lacking that recognition.

They recommended avoiding oversimplifying CAD when considering MI and mortality risks, instead using overall extent of CAD to predict outcomes and manage risks in patients. Further, Maddox et al suggested future investigations were needed to better quantify CAD and create outcome risk groups.