Editor's Note: Commentary based on Blanke P, Naoum C, Ahmadi A, et al. Long-term prognostic utility of coronary CT angiography in stable patients with diabetes mellitus. JACC Cardiovasc Imaging 2016;9:1280-8.

Background:

Several studies have shown that diabetic patients are at increased cardiovascular risks compared to non-diabetic populations. However, the prognostic value of the coronary CT angiography in patients with diabetes compared to non-diabetics has not been elucidated.

Methods:

This study was performed in the context of the CONFIRM Registry, a prospective, multicenter, observational cohort study designed to examine the relationship of coronary atherosclerosis evaluated by coronary CTA and clinical risk factors to adverse outcomes. Participants in the study had no known history of CAD. Patients underwent at least a 64 slice coronary CTA and had a 5 year follow up.

Results:

The association of coronary atherosclerosis with all-cause and cardiovascular mortality risks was examined in 1823 patients with diabetes and compared to 1823 propensity-matched patients without diabetes (mean age of 62 years). Among the diabetics, 24% had no evidence of CAD, 23% had non obstructive CAD and 52% had obstructive CAD. In comparison, 29% of non-diabetics had no evidence of CAD, 30% had non obstructive CAD and 40% had obstructive CAD. During a follow-up of 5 years, there were no significant difference in all-cause mortality among DM and non DM patients in the absence of CAD on coronary CTA. However, compared with non DM, diabetics had more than double the adjusted risk of all-cause mortality in the presence of non-obstructive (HR: 2.07; p = 0.001) and obstructive CAD (HR: 2.22; p < 0.001).

Conclusion:

Non-obstructive and obstructive CAD according to coronary CTA in diabetic patients compared to nondiabetic patients were associated with higher rates of all-cause mortality and major adverse cardiovascular events at 5 years. However, in the absence of CAD according to coronary CTA, diabetic and non-diabetics patients were at comparable risk.

Commentary/Perspective:

Dr. Blanke and colleagues performed an interesting observational study examining the prognostic value of the coronary CT angiography in patients with diabetes compared to non-diabetics. As pointed out by the authors, key findings from this effort include the following: 1) absence of CAD based on coronary CT was associated with a low overall annual mortality; 2) diabetic and non-diabetic patients are at similar mortality risk in the absence of CAD; 3) diabetic patients with non-obstructive and obstructive CAD have higher risk of all-cause mortality and major adverse cardiovascular events compared to non-diabetics; 4) with a poorer prognosis in patients with increasing severity of CAD. This is an important study that elucidates the prognostic value of coronary CT angiography in stable patients with diabetes. An important clinical take-home from this paper is that coronary CTA can be utilized to further risk stratify stable patients with diabetes who have no known CAD. Data from this paper will impact the long term follow up of DM patients with non-obstructive disease and the importance of aggressive therapy for atherosclerosis prevention.

Beyond this elegant finding, this paper provides several addition important insights. DM patients with nonobstructive CAD have a significantly worse survival than those without atherosclerosis and survival that is comparable to patients with DM with 1-vessel obstructive disease and to nondiabetic subjects with multivessel obstructive CAD. A possible explanation, based on several studies, is that the majority of acute coronary syndromes result from vulnerable plaques that are angiographically reported to be mild. Data from this paper advance our understanding of the prognostic significant of any atherosclerosis in DM patients.

From our perspective, within the limitations of an observational study, the conclusions from this study can be summarized as follows: 1) coronary CT can be used in diabetic patients for further risk stratification in addition to other traditional cardiovascular risk factors; 2) any degree of atherosclerosis in DM patients is associated with worse outcome; 3) non obstructive CAD in DM patients is the tip of the iceberg and should be treated aggressively. Furthermore, any evidence of atherosclerosis in a diabetic patient based on a coronary CTA can serve as a motivation for the patient to be more complaint with medical treatment and make healthy lifestyle changes. Data from this study may encourage physicians to be more aggressive in the treatment of the patient with DM to prevent atherosclerosis. Finally, the role of coronary CTA to stratify therapy according to presence or absence and extent of CAD needs further assessment and deserves future investigation.

Keywords: Acute Coronary Syndrome, Atherosclerosis, Cardiovascular Diseases, Angiography, Coronary Angiography, Coronary Artery Disease, Diabetes Mellitus, Life Style, Registries, Risk Factors, Tomography, X-Ray Computed, Metabolic Syndrome

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