To the Editor In the Clinical Evaluation of Magnetic Resonance Imaging in Coronary Heart Disease 2 (CE-MARC 2) trial, Dr Greenwood and colleagues1 addressed the question of whether CMR can reduce the number of unnecessary invasive coronary angiographies in patients with suspected CHD compared with a myocardial perfusion scintigraphy (MPS)–guided approach and with the NICE guidelines, which also integrate cardiac computed tomography in the evaluation of lower-risk patients. However, I was concerned that per protocol, inconclusive and negative noninvasive imaging test results (which should not be followed by invasive angiography) could be overruled by the responsible physician and such patients could undergo angiography. In the CMR group, 54 tests were positive but 85 invasive angiograms were performed, suggesting 31 patients (36%) with a normal CMR test received invasive angiography. Conversely, in the MPS group, 81 patients had a positive result and 78 had an angiogram. The fact that the referring physician could overrule the imaging findings added an important potential bias, as proceeding with invasive angiography in patients with normal CMR examinations will likely increase the percentage of unnecessary angiograms. In CE-MARC 2, the ability to overrule the test result was defined per protocol and thus, these patients must be kept in the analyses. Hence, the authors should not conclude that the diagnostic performances of CMR and MPS are not statistically significantly different, although such a difference has been shown in a large single-center trial2 and international multicenter multivendor trials.3,4 They perhaps could conclude that the participating physicians did not strongly believe in the diagnostic performance of CMR, although they were comfortable with the MPS performance.
Schwitter J. Alternatives in the Evaluation of Suspected Coronary Heart Disease. JAMA. 2017;317(2):211-212. doi:10.1001/jama.2016.18326