November 4th, 2014

Nonobstructive Coronary Artery Disease Linked to Elevated Risk

A large number of people who undergo elective coronary angiography are found to have nonobstructive coronary artery disease, and these patients have significantly increased risk for myocardial infarction and death, according to a retrospective study published in JAMA.

Thomas Maddox and colleagues analyzed data from nearly 38,000 elective angiography patients in the VA health system. More than half (55.4%) were found to have obstructive CAD, while 22.3% were found to have nonobstructive CAD. At 1 year, the risk for MI and death was elevated based on the severity and extent of the CAD. Compared with people with no CAD, the risk for MI was 2 to 4.5 times greater in the patients with nonobstructive CAD. The risk continued to rise with obstructive disease, so that people with obstructive 3-vessel or left main disease had nearly 20 times the risk for MI.

The findings, write the authors, “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.” The results also “reveal the limitations of a dichotomous 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.”

Despite the increased level of risk associated with nonobstructive disease, the major prevention studies have only included patients who had had clinical events or who had obstructive CAD. “The stable nonobstructive CAD patient population was systematically excluded from these studies,” the authors write. “Thus, empirical evidence is lacking as to whether these patients benefit from the prevention therapies recommended for their obstructive CAD counterparts.”

Cardiologists will not be surprised by the findings. It is well known that most MIs occur in vessels with nonobstructive lesions, said L. David Hillis. Rick Lange offered the following take-away messages about the study:

I agree that (a) any CAD is associated with an increased risk of CV events; (b) the risk of CV events tracks with burden of disease; (c) the distinction of obstructive vs nonobstructive may be helpful in determining whether revascularization may improve symptoms (and in the occasional patient, survival); and (d) the presence of CAD (rather than the extent of obstruction) should drive our decision to prescribe medical therapy (ie, aspirin, statins, etc) that reduces the risk of MI or CV death.





3 Responses to “Nonobstructive Coronary Artery Disease Linked to Elevated Risk”

  1. Jonathan Hemphill, MD,FACC says:

    Thanks Larry, for the nice review. Rick’s takeaway points are spot on. Every patient with non obstructive CAD needs to apply aggressive risk factor modification strategies. Patients need to be educated about the importance of these strategies so that they can maintain or improve the quality of their lives and live longer as well. Often missing, is how important diet is in maintaining our health and how eating more whole unprocessed foods can make a difference.

  2. The absence of observable disease by angiography does not completely rule out non-obstructive disease where the lumen remains normal in size but the wall of the vessel bulges outward as noted by Glagov a few decades ago. This phenomenon is not uncommon when CT angiography is employed to evaluate vessel anatomy.

    Whereas subjects with significant obstruction are at higher risk for MI, the majority of heart attacks occur in subjects without obstructive disease, who had no symptoms prior to the plaque rupturing and the vessel obstructing with thrombus.

    Comparing the above results to what has been seen with the use of coronary calcium imaging creates a strong argument for increased use of CAC screening and a reduced use of stress imaging and angiography.

    A coronary calcium score of 0 is associated with an annual MI rate of 20% annual rate of MI. If we know a person has a calcium score high enough to justify treatment, why would we feel any need to seek out obstructive disease unless there are life altering symptoms?

  3. Edina Cenko, MD says:

    These data were well established on the bases of a pooled analysis of TIMI trials published on Arch Intern Med. 2006;166:1391-5 by Bugiardini et colleagues. Greater emphasis on these previous data and possible differences or extension should have been provided by the authors