REVIEW ARTICLE Reconciling discordant myocardial perfusion imaging and coronary angiography Joyce Rollor, MD, a Rebecca Feldmeier, MD, b Scott Jerome, DO, a and Anuj Gupta, MD a a Division of Cardiovascular Medicine, University of Maryland Medical Center, Baltimore, MD b Department of Internal Medicine, University of Maryland Medical Center, Baltimore, MD Received Dec 18, 2015; accepted Dec 18, 2015 doi:10.1007/s12350-016-0396-4 A common clinical conundrum presents itself in the discordance between nuclear stress testing and invasive coronary angiography (ICA) in the patient presenting with angina. A patient with an abnormal perfusion scan and ‘‘normal coronary angiography’’ may result in the patient’s symptoms being dismissed as ‘‘non-cardiac.’’ Alternatively, a patient with a ‘‘normal perfusion study,’’ who nonetheless undergoes ICA and is found to have significant coronary artery disease may confound efforts to risk stratify and potentially treat patients with angina. This paper will review the current evidence to explain these apparent paradoxical scenarios. (J Nucl Cardiol 2016) Key Words: Coronary artery disease Æ myocardial perfusion imaging: SPECT Æ fractional flow reserve Æ invasive coronary angiography Æ coronary flow reserve Abbreviations CAD Coronary artery disease CFR Coronary flow reserve FFR Fractional flow reserve ICA Invasive coronary angiography IMR Indices of microcirculatory resistance IVUS Intravascular ultrasound LAD Left anterior descending coronary artery MPI Myocardial perfusion imaging PCI Percutaneous coronary intervention SSS Summed rest score ABNORMAL STRESS TESTING WITH NORMAL CORONARY ARTERIES The contradiction between patients with an abnor- mal stress test and ‘‘normal coronary arteries’’ is perplexing, for both the physician caring for the patient, and the patient who is told that the stress test is falsely abnormal. This section will discuss the prognostic implications of non-obstructive coronary angiography, review the importance of other pertinent findings in a patient with non-obstructive CAD, and attempt to reconcile perfusion abnormalities with a ‘‘normal’’ fractional flow reserve (FFR). Non-obstructive CAD Stress testing as a risk stratification tool to deter- mine which patients with either stable angina or unstable angina with negative cardiac enzymes should undergo ICA is guideline driven. 1 Despite this recom- mendation, in patients without known coronary disease referred for ICA, 39% were reported to have normal coronary arteries, as opposed to 37% of patients who were found to have obstructive coronary disease. 2 Obstructive coronary disease was defined as a stenosis of greater than 50% in the left main coronary artery (LAD), or greater than 70% in a major epicardial Reprint requests: Anuj Gupta, MD, Division of Cardiovascular Med- icine, University of Maryland Medical Center, Baltimore, MD; agupta@medicine.umaryland.edu 1071-3581/$34.00 Copyright Ó 2016 American Society of Nuclear Cardiology.