The following are key points to remember from this state-of-the-art paper on cardiovascular imaging techniques to assess microvascular dysfunction:

1. There are a large amount of data on identification and management of epicardial coronary artery disease (CAD). In contrast, microvascular disease (MVD) can be challenging to diagnose and can be present in both obstructive and nonobstructive epicardial CAD.
2. Myocardial blood flow is defined as blood flow through coronary vessels over time, and there are multiple mechanisms for this to autoregulate under different physiologic conditions. The presence of MVD can disrupt the ability of myocardial blood flow to adapt to different conditions. MVD can include any process that disrupts microvascular function, including endothelial dysfunction, coronary spasm, inflammation, and atherosclerosis.
3. Administration of vasodilating medications such as adenosine are often used to evaluate for MVD. A reduced ratio of coronary flow under maximal hyperemic conditions to baseline flow defines reduced coronary flow reserve (CFR) on invasive measurements. CFR represents both epicardial stenoses and MVD; in the absence of obstructive epicardial stenosis, a reduced CFR indicates MVD.
4. Myocardial perfusion reserve (MPR) is analogous to CFR for noninvasive imaging, and measures flow through the myocardium. This can be assessed on multiple different imaging modalities. Concentration-time curves of a contrast agent are generated at rest and with vasodilation and can be used to quantify myocardial blood flow.
5. Contrast echocardiography and Doppler echocardiography can evaluate for MVD and are very safe. However, they are operator dependent, can be limited by difficult images, and there are a lack of robust data supporting their use.
6. Computed tomography (CT) perfusion can diagnose MVD and can simultaneously assess for CAD on the same study. However, protocols using dynamic perfusion require repeated imaging and expose patients to high radiation doses. The need for iodinated contrast can be associated with risk of renal injury.
7. Positron emission tomography (PET) is the most validated modality to evaluate MVD in the absence of obstructive CAD. There are robust prognostic data for this test, and it has good reproducibility and accuracy. Radiation dose is relatively low for this study. This test has high cost and has limited availability.
8. Single-photon emission computed tomography has wider availability than PET or cardiac magnetic resonance imaging (CMR), although evaluation of MVD requires upgraded equipment and is associated with higher radiation doses. This test has limited validation of MVD in nonobstructive CAD, which limits its clinical utility at present.
9. Assessment of MVD by CMR is validated against invasive tests and PET and is associated with no radiation exposure. However, it is expensive, is not widely available, and has limited prognostic data at present.
10. Although many imaging modalities can be used to evaluate for MVD, PET has the most prognostic data at present. Significant future research is needed to compare the relative accuracy and prognostic importance of MVD identified on these imaging modalities, and to assess whether medications and other interventions impact symptoms and outcomes.

Clinical Topics: Heart Failure and Cardiomyopathies, Noninvasive Imaging, Stable Ischemic Heart Disease, Atherosclerotic Disease (CAD/PAD), Acute Heart Failure, Computed Tomography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging, Chronic Angina

Keywords: Adenosine, Atherosclerosis, Constriction, Pathologic, Coronary Artery Disease, Diagnostic Imaging, Echocardiography, Echocardiography, Doppler, Heart Failure, Inflammation, Magnetic Resonance Imaging, Microvascular Angina, Myocardium, Positron-Emission Tomography, Radiation Dosage, Tomography, X-Ray Computed, Vasodilation

< Back to Listings