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Stress Testing vs. CT Angiography in Diabetics With CAD
Study Questions:
What is the optimal noninvasive diagnostic strategy in patients with diabetes and suspected coronary artery disease (CAD)?
Methods:
This is a post hoc analysis of the PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) trial, which randomized 10,003 patients with stable symptoms concerning for CAD to coronary computed tomography angiography (CCTA) or functional testing (exercise electrocardiogram, stress echocardiogram, or stress nuclear imaging). Of the 8,966 (89.6%) with an interpretable noninvasive testing result, 1,908 had diabetes. Outcomes evaluated included invasive coronary angiography within 30 days, medication prescription (aspirin, statin, beta-blockers, and angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers) within 60 days, and two composite clinical outcomes (death/myocardial infarction [MI]/hospitalization for unstable angina and cardiovascular [CV] death/MI).
Results:
Diabetics were more likely to have an abnormal noninvasive test (15.2% vs. 11.5%, p < 0.001). Diabetics who underwent CCTA as opposed to functional testing had a lower risk of death from CV death/MI than diabetics who underwent functional testing (hazard ratio [HR], 0.38; 95% confidence interval [CI], 0.18-0.79; p = 0.01). This was largely driven by a lower rate of MI in patients with diabetes who underwent CCTA compared to functional testing (0.2% vs. 1.3%). However, the rate of MI in diabetics was also lower than the rate of MI among nondiabetics who underwent CCTA (0.2% vs. 0.7%). Importantly, there was no statistically significant difference between diabetics who underwent CCTA and functional testing for the broader outcome of death, MI, or hospitalization for unstable angina (HR, 0.74; 95% CI, 0.47-1.18; p = 0.207).
Conclusions:
The authors concluded that among diabetic patients, CCTA is associated with less CV death and MI than functional testing.
Perspective:
One concern in this analysis is that the authors exclude data post-randomization based on interpretability of imaging. This breaks the intention-to-treat principle under which all randomized patients should be analyzed based on the assigned arm rather than only on those who received the assigned diagnostic procedure or treatment. For example, patients with extensive calcific CAD are more likely to have a nondiagnostic CCTA but are also more likely to experience adverse events. Consequently, excluding these subjects may make the prognosis in the CCTA arm seem significantly better than the functional testing arm. This is evidenced by the greater than threefold lower rate of MI in diabetics versus nondiabetics in the CCTA arm.
Interestingly, this study chose endpoints different from the overall trial published in the New England Journal of Medicine. The endpoint closest to the prespecified primary endpoint of the overall trial of death, MI, or hospitalization for unstable angina did not show a benefit to CCTA over functional testing. This endpoint omits major procedural complications as part of the composite (which was part of the overall study). Given higher rates of angiography and revascularization in CCTA, this omission could have had a significant impact on the conclusions.
Also, among many patients with an abnormal stress test, only 73.5% of diabetics were placed on statin therapy at 60 days compared with 85.8% of those diabetics who had an abnormal CCTA. These data suggest that there is opportunity to educate physicians about the strongly beneficial role of optimal medical therapy in patients with diabetes and evidence of CAD.
Clinical Topics: Cardiac Surgery, Cardiovascular Care Team, Dyslipidemia, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Atherosclerotic Disease (CAD/PAD), Cardiac Surgery and Arrhythmias, Nonstatins, Novel Agents, Statins, Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Computed Tomography, Echocardiography/Ultrasound, Nuclear Imaging
Keywords: Angina, Unstable, Angiotensin Receptor Antagonists, Angiotensin-Converting Enzyme Inhibitors, Aspirin, Chest Pain, Coronary Angiography, Coronary Artery Disease, Diabetes Mellitus, Diagnostic Imaging, Echocardiography, Stress, Electrocardiography, Exercise Test, Hydroxymethylglutaryl-CoA Reductase Inhibitors, Myocardial Infarction, Myocardial Ischemia, Myocardial Revascularization, Primary Prevention, Tomography, X-Ray Computed
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