The following are key points to remember from this JACC review topic of the week on stress cardiac magnetic resonance imaging (CMR):

1. Stress CMR is most often performed with a vasodilator: adenosine, regadenoson, or dipyridamole. After vasodilator administration, a gadolinium-based contrast agent (GBCA), functioning as a blood flow tracer, is injected into a peripheral vein, and T1-weighted dynamic stress perfusion images are acquired in short-axis planes. Contrast enters myocardial segments with normal perfusion more rapidly and fully than those with abnormal perfusion. A perfusion defect appears as a hypointensity along the subendocardium in a coronary distribution.
2. Late gadolinium enhancement (LGE) images, acquired at the end of a typical stress CMR protocol, allow for identification of prior myocardial infarction (MI). Interpreting stress perfusion images in conjunction with LGE images, as well as cine images (which demonstrate wall motion), allows readers to distinguish between ischemia and infarction.
3. The excellent diagnostic accuracy of stress CMR was demonstrated in the recent GadaCad (Gadobutrol-Enhanced CMR to Detect Coronary Artery Disease) trial. Compared with a reference standard of invasive coronary angiography or coronary computed tomography angiography, stress CMR had sensitivities of 79% and 87%, and specificities of 87% and 73%, for single- and multi-vessel coronary artery disease, respectively. As a result of GadaCad, gadobutrol became the first GBCA to gain approval from the US Food and Drug Administration for stress CMR.
4. The SPINS (Stress CMR Perfusion Imaging in the United States) registry demonstrated the prognostic utility of stress CMR. Patients without evidence of ischemia or infarction on stress CMR had a 99.3% event-free rate over a 5.5-year follow-up period. Patients with both ischemia and infarction were at highest risk of cardiovascular death or nonfatal MI. Multiple studies have shown that CMR improves risk reclassification of patients at intermediate risk of stable ischemic heart disease.
5. Quantitative analysis of myocardial perfusion with stress CMR can improve diagnostic utility and better differentiate between single- and multi-vessel disease than visual analysis alone. This is analogous to quantification of myocardial blood flow and coronary flow reserve with vasodilator rubidium positron emission tomography (PET).
6. As compared with single-photon emission computed tomography (SPECT), which is much more commonly used in the United States, stress CMR offers several technical advantages. Because of CMR’s superior spatial resolution, larger field of view, and better tissue differentiation, it is not limited by attenuation artifacts or contamination of the myocardium by other signal sources as on SPECT (for instance, excessive uptake of radiotracer by the gut creating the appearance of an inferior wall perfusion defect). Because stress CMR can identify subendocardial ischemia, it is less susceptible to balanced ischemia (deceptively normal perfusion images in the presence of multivessel ischemia) than SPECT. Additionally, stress CMR does not expose patients to ionizing radiation, so it may be advantageous in younger patients and those who are expected to require multiple scans over time.
7. It is a common misperception that all GBCAs are contraindicated in the setting of severe kidney disease due to risk of nephrogenic systemic fibrosis (NSF). However, this disorder was previously observed in patients who had received linear GBCAs. Macrocyclic GBCAs currently in use for CMR, including gadobutrol and gadoteridol, have not been associated with NSF.
8. Disadvantages of stress CMR include limited availability in the United States and inability to include an exercise component. While claustrophobia may make some patients reluctant to undergo stress CMR, low-dose oral sedation or conscious sedation by an anesthesia team is often feasible. Though LGE imaging is feasible for patients with cardiac implantable electronic devices, vasodilator stress CMR is not because of artifacts.

Clinical Topics: Geriatric Cardiology, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Atherosclerotic Disease (CAD/PAD), Acute Heart Failure, Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Computed Tomography, Magnetic Resonance Imaging, Nuclear Imaging

Keywords: Coronary Angiography, Coronary Artery Disease, Diagnostic Imaging, Gadolinium, Geriatrics, Heart Failure, Magnetic Resonance Imaging, Myocardial Infarction, Myocardial Ischemia, Myocardium, Nephrogenic Fibrosing Dermopathy, Perfusion, Perfusion Imaging, Positron-Emission Tomography, Radiation, Ionizing, Single Photon Emission Computed Tomography Computed Tomography, Vasodilator Agents

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