For decades, the paradigm for assessing ischemic coronary artery disease has been a sequential approach of noninvasive functional testing followed by an anatomic delineation of the disease through invasive coronary assessments for appropriate patients. While this approach facilitates further prognostication for higher-risk patients while allowing lower-risk patients to avoid invasive procedures, conventional noninvasive functional testing is not perfectly accurate. As such, not all patients who are higher risk based on functional testing have anatomically severe disease. Conversely, not all eligible patients with anatomically severe coronary artery disease are referred for a cardiac catheterization because of an underestimation of risk during upstream functional testing.
The ability to combine anatomic and functional assessments in a single noninvasive test has the theoretical benefit of providing greater accuracy and confidence in risk stratification. Computed tomography (CT) angiography with adjunctive noninvasively assessed fractional flow reserve (FFR) derived through computational fluid dynamic modeling implements this approach to assessing coronary artery disease. Computed tomography with FFR adds diagnostic accuracy when compared with conventional CT angiography using the gold standard of invasively assessed FFR.1
In this issue of JAMA Cardiology, Cook et al2 perform a systematic review of studies assessing the diagnostic accuracy of CT-FFR compared with invasive FFR. Beyond assessing overall accuracy, the authors specifically sought to determine whether there is variability in the performance characteristics of CT-FFR at specific ranges of FFR. This is especially relevant when interpreting the results of individual clinical studies, because sufficient confidence is required in any test that is proposed as a potential surrogate of invasive coronary assessments, especially for patients with lesions that would afford them either a prognostic or quality-of-life benefit through undergoing a coronary revascularization.
While this review retains the important caveat of a lack of the individualized patient data provided by original study investigators, the authors were able to perform analyses assessing the accuracy of CT-FFR across a range of FFR values. As discussed by Shaw and Nicol,3 CT-FFR performed best at the outer ranges of FFR values rather than within the intermediate range of 0.7 to 0.8. Whether avoiding (or performing) angiography in patients with CT-FFR values within this range is safe/effective can only be determined through larger prospective studies that assess the clinical outcomes of these approaches. Until these studies are conducted, the clinical significance of the observation of Cook and colleagues2 is that for patients in whom CT-FFR results fall within an intermediate range, clinical judgment is even more paramount.
Corresponding Author: Ajay J. Kirtane, MD, SM, 161 Fort Washington Ave, 6th Floor, New York, NY 10032 (email@example.com).
Conflict of Interest Disclosures: The author has completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Kirtane reports receiving institutional research grants to Columbia University from Boston Scientific, Medtronic, Abbott Vascular, Abiomed, Cardiovascular Systems, Siemens, and CathWorks. No other disclosures are reported.
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