Veterans with Non-Obstructive Coronary Artery Disease at Significantly Greater Risk of MI and Mortality
BACKGROUND:
Non-obstructive coronary artery disease (CAD) is atherosclerotic plaque that would not be expected to obstruct blood flow or result in anginal symptoms, so its presence has been characterized as "insignificant" or "no significant CAD" in the medical literature. However, this perception may be incorrect, as prior studies have noted that the majority of plaque ruptures and resultant myocardial infarctions (MIs) arise from non-obstructive plaques. This retrospective study compared incidence of MI and mortality between patients with non-obstructive CAD, obstructive CAD, and no apparent CAD in a national cohort of Veterans receiving VA care. Using VA data, investigators identified all Veterans undergoing elective coronary angiography for CAD between FY07 and FY12 in the VA healthcare system. Among 37,674 Veterans undergoing the procedure, 8,384 (22%) had non-obstructive CAD and 20,899 (55%) had obstructive CAD. Patients were further categorized by CAD severity in terms of the extent of CAD (e.g., 1-, 2-, or 3-vessel involvement). In addition to rates of one-year hospitalization for non-fatal MI after the index angiography, outcomes were one-year all-cause mortality and combined one-year MI and mortality. Other variables included demographics and cardiovascular risk factors.
FINDINGS:
- Compared to Veterans with no apparent CAD, Veterans with non-obstructive CAD were at significantly greater risk of myocardial infarction (MI) and all-cause mortality at one year.
- The one-year risk of MI progressively increased by extent of CAD, rather than abruptly increasing between non-obstructive and obstructive CAD. For example, among Veterans with no apparent CAD, the one-year MI rate was 0.11%, while the one-year MI rate for 1-vessel non-obstructive CAD was 0.24%, increasing to 0.59% for 3-vessel non-obstructive CAD.
- One-year mortality rates also were associated with increasing extent of CAD, ranging from 1.4% among Veterans with no apparent CAD to 4% for Veterans with 3-vessel or LM (left main) obstructive CAD. After risk adjustment, there was no significant association between 1- or 2-vessel non-obstructive CAD and mortality, but there were significant associations with mortality for 3-vessel non-obstructive CAD and 1-, 2-, and 3-vessel or LM obstructive CAD.
- Age and cardiovascular risk factors (e.g., hypertension, hyperlipidemia, and diabetes) all increased with increasing extent of CAD. The frequency of prescriptions for post-angiography cardiovascular medications and rates of coronary revascularization also increased with CAD extent.
LIMITATIONS:
- Criteria by which Veterans were selected to undergo coronary angiograms are variable and likely underestimate the true prevalence of non-obstructive CAD among patients not undergoing angiography.
- The association between CAD extent and MI and mortality rates could be confounded by factors other than CAD burden.
IMPLICATIONS:
- Findings suggest that non-obstructive CAD is common, confers significant risk for MI and mortality, and warrants immediate consideration of preventative therapies for patients with this condition.
AUTHOR/FUNDING INFORMATION:
Drs. Maddox and Bradley were supported by HSR&D Career Development Awards, and are part of HSR&D's Center for Innovation for Veteran-Centered and Value-Driven Care, Denver, CO.
Maddox T, Stanislawski M, Grunwald G, Bradley S, et al. Non-obstructive Coronary Artery Disease and Risk of Myocardial Infarction. JAMA. November 5, 2014;312(17):1754-63.
