Anatomical versus Functional Testing for Coronary Artery Disease

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Jul 2, 2015 - Daniel M. Blumenthal, M.D., M.B.A.. Jason H. Wasfy, M.D., M.Phil. Massachusetts General Hospital. Boston, MA [email protected].
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Anatomical versus Functional Testing for Coronary Artery Disease To the Editor: In the PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain), Douglas et al. (April 2 issue)1 describe the clinical outcome of patients with chest pain and suspected coronary artery disease (CAD) who were assigned to undergo either anatomical testing with the use of coronary computed tomographic angiography (CTA) or functional testing. The authors report that the clinical outcome did not differ between the two strategies, whereas the mean (±SD) radiation exposure in the CTA group was higher (cumulatively, 12.0±8.5 mSv), with 98% undergoing CTA. In our high-volume center, the mean radiation exposure after complete CTA (including calcium score and angiography) in 1560 outpatients with chronic chest pain was 2.4±2.0 mSv.2 All investigations were performed with a high-end 2×128-slice scanner and with FLASH protocol performed in 72% of patients and prospective scanning in 25%. Whereas in PROMISE only 34% of patients in the CTA group underwent scintigraphy and 12% underwent invasive angiography, more than 80% of the patients had radiation exposure of more than 5 mSv (Fig. S3 in the Supplementary Appendix of the article, available with the full text of the article at NEJM.org). These numbers suggest that the higher radiation burden in the CTA group may not be the result of the selection of patients (i.e., those with an increased body-mass index) but, rather, may be related to CTA scanning–related characteristics in the various participating centers. A detailed overview of these characteristics could provide useful insight. Michiel J. Bom, M.D. Petrus M. van der Zee, M.D., Ph.D. Jan H. Cornel, M.D., Ph.D. Medical Center Alkmaar Alkmaar, the Netherlands [email protected]

No potential conflict of interest relevant to this letter was reported. 1. Douglas PS, Hoffmann U, Patel MR, et al. Outcomes of

anatomical versus functional testing for coronary artery disease. N Engl J Med 2015;372:1291-300. 2. Bom MJ, van der Zee PM, Cornel JH, van der Zant FM, Knol RJJ. Diagnostic and therapeutic usefulness of coronary computed tomography angiography in out-clinic patients referred for chest pain. Am J Cardiol 2015 April 6 (Epub ahead of print). DOI: 10.1056/NEJMc1505594

To the Editor: Douglas et al. report no difference in outcomes among symptomatic patients who underwent anatomical versus functional testing for CAD. However, only 10.2% of the patients in the functional-testing group in this lowrisk population were evaluated with exercise electrocardiography (ECG), which requires no radiation and is much less expensive than nuclear imaging, which was performed in 67.5% of patients. Furthermore, 29.4% of the patients were evaluated with pharmacologic testing. Although this probably reflects clinical practice in the United States, what percentage of patients who underwent nuclear imaging and stress echocardiography met the appropriate-use criteria for this week’s letters  89 Anatomical versus Functional Testing for Coronary Artery Disease  91 Vaccine against Pneumococcal Pneumonia in Adults  93 Chikungunya Virus Infections  95 Fibrosis — A Common Pathway to Organ Injury and Failure  96 Real-Time Localization of Parathyroid Adenoma during Parathyroidectomy

n engl j med 373;1 nejm.org july 2, 2015

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cardiac imaging? Exercise capacity,1 the Duke Treadmill Score,2 heart rate recovery,3 peak heart rate,4 and ventricular dysrhythmias are robust predictors of the risk of death. This information is available at low cost and requires no radiation exposure or imaging. Thus, rigorous exercise ECG testing by knowledgeable practitioners could be noninferior or superior for outcome prediction and much more cost-effective than cardiac imaging in patients with an interpretable stress ECG who are able to exercise. Wade H. Martin III, M.D.

nary flow reserve, and whether patients received a trial of medical therapy before undergoing revascularization — is critical for understanding the significant difference in revascularization rates observed in PROMISE. Daniel M. Blumenthal, M.D., M.B.A. Jason H. Wasfy, M.D., M.Phil.

St. Louis Veterans Administration Medical Center St. Louis, MO [email protected] No potential conflict of interest relevant to this letter was reported.

transitioning from a focus on individual lesions to atherosclerotic disease burden for coronary artery disease risk assessment. J Am Coll Cardiol 2015;65:846-55. 2. De Bruyne B, Fearon WF, Pijls NHJ, et al. Fractional flow reserve–guided PCI for stable coronary artery disease. N Engl J Med 2014;371:1208-17.

1. Myers J, Prakash M, Froelicher V, Do D, Partington S, Atwood

JE. Exercise capacity and mortality among men referred for exercise testing. N Engl J Med 2002;346:793-801. 2. Mark DB, Shaw L, Harrell FE Jr, et al. Prognostic value of a treadmill exercise score in outpatients with suspected coronary artery disease. N Engl J Med 1991;325:849-53. 3. Cole CR, Blackstone EH, Pashkow FJ, Snader CE, Lauer MS. Heart-rate recovery immediately after exercise as a predictor of mortality. N Engl J Med 1999;341:1351-7. 4. Lauer MS, Francis GS, Okin PM, Pashkow FJ, Snader CE, Marwick TH. Impaired chronotropic response to exercise stress testing as a predictor of mortality. JAMA 1999;281:524-9. DOI: 10.1056/NEJMc1505594

Massachusetts General Hospital Boston, MA [email protected] No potential conflict of interest relevant to this letter was reported. 1. Arbab-Zadeh A, Fuster V. The myth of the “vulnerable plaque”:

DOI: 10.1056/NEJMc1505594

To the Editor: Douglas et al. conclude that in symptomatic patients with suspected CAD, initial CTA, as compared with initial functional testing, did not improve clinical outcomes at a median follow-up of 2 years. Obviously, it is not the diagnostic tests themselves that influence outcomes but, rather, the ability of such testing to lead to an intervention (medical therapy with or without revascularization). Therefore, can the authors report the rate and dose of lipid-lowering and antiplatelet therapy at 12-month and 24-month follow-up in each group and compare these values with those at baseline? This would be interesting, given the lower rate of death or nonfatal myocardial infarction at 12 months in the CTA group and is particularly relevant in light of previous data showing that identification of any degree of CAD on CTA leads to greater use of lipidlowering and antiplatelet therapy,1 including in a direct comparison with functional testing.2 Furthermore, Douglas et al. report a higher revascularization rate in the initial CTA group. The effect on outcomes of both medical therapy and revascularization, which are both influenced by the initial investigation strategy, may not become evident until longer-term follow-up.

To the Editor: PROMISE raises important questions about the relative value of coronary CTA and stress testing for patients with symptoms suggestive of stable coronary disease. One such question is whether CTA contributes to unhelpful downstream service use, reducing value for patients. Although the study was not powered to identify differences in revascularization rates (or to determine whether revascularization has an effect on clinical outcomes), the marked disparity in revascularization rates between the CTA group and the functional-testing group (311 patients vs. 158 patients, P