1. Patients with non-obstructive coronary obstructive disease (CAD) had a significantly higher risk of developing an MI within the next year compared to those with no apparent CAD.
2. One-year all cause mortality in patients with non-obstructive CAD was only significantly increased in those with 3-vessel involvement.
Evidence Rating Level: 2 (Good)
Study Rundown: Non-obstructive CAD, defined as the presence of atherosclerotic plaques in the coronary arteries that do not significantly impede blood flow, has been previously shown to give rise to a majority of plaque ruptures and myocardial infarctions (MI). However, the most of the literature on myocardial infarction has nevertheless focused on obstructive CAD patients rather than those with non-obstructive CAD. This study aimed to examine this often overlooked patient population and confirmed that non-obstructive CAD is a significant health issue and that it is associated with a higher 1-year incidence of myocardial infarctions (MI) and 1-year all-cause mortality when compared to absence of CAD.
Strengths of the study include the large sample cohort. By examining patients undergoing elective catheterization rather than diagnostic catheterization, authors designed the study to include asymptomatic patients who are most likely to benefit from preventative measures. Weaknesses of this study related to its use of the VA population as the study cohort and included the low numbers of female patients and the inability to assess for cardiac-specific mortality through the VA electronic health record. Ultimately, however, this study emphasizes the significance of non-obstructive CAD in cardiac health and underscores the need for further research on this topic.
Relevant Reading: Pathophysiology of Coronary Artery Disease
In-Depth [retrospective cohort]: This is a retrospective cohort study that included 37,674 patients with no past history of CAD or CAD events who underwent elective cardiac catheterization at the 79 VA catheterization laboratories across the country. Indications for catheterization included chest pain, stable angina, ischemic heart disease, and/or any cardiac stress test that indicated presence of ischemia. Non-obstructive CAD was defined as coronary artery stenosis between 20-50% in the left main artery and between 20-70% in all other major arteries. Patients were categorized into 7 subgroups: no CAD, 1 vs. 2 vs. 3-vessel non-obstructive CAD, and 1 vs. 2 vs. 3-vessel obstructive CAD. Primary outcome was defined as 1-year hospitalization for nonfatal MI. Secondary outcomes were 1-year all-cause mortality and combined 1-year incidence of MI and mortality.
Results showed that with risk adjustment for various co-morbidities, there was a significant association with MI for 2-vessel non-obstructive CAD (HR 4.6, 95%CI 2.0-10.5) and more severe CAD and no significant association with MI for 1-vessel non-obstructive CAD (HR 2.0, 95%CI 0.8-5.1) and absence of CAD. For the two secondary outcomes, significant association was seen with 3-vessel non-obstructive CAD and more severe CAD. Presence of diabetes or presence of symptoms increased outcome rates but did not alter the trend with increasing CAD extent.
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