134. Nuclear and Multimodality Imaging: Cardiac Sarcoidosis

CardioNerd Amit Goyal is joined by Dr. Erika Hutt (Cleveland Clinic general cardiology fellow), Dr. Aldo Schenone (Brigham and Women’s advanced cardiovascular imaging fellow), and Dr. Wael Jaber (Cleveland Clinic cardiovascular imaging staff and co-founder of Cardiac Imaging Agora) to discuss nuclear and complimentary multimodality cardiovascular imaging for the evaluation of cardiac sarcoidosis. Show notes created by Dr. Hussain Khalid (University of Florida general cardiology fellow and CardioNerds Academy fellow in House Thomas). To learn more about multimodality cardiovascular imaging, check out Cardiac Imaging Agora!

Cardiac sarcoidosis is a leading cause of morbidity and mortality for patients with sarcoidosis. A high index of suspicion is needed for the diagnosis as it is often recognized late or unrecognized. It is difficult to diagnose given the focal nature of the cardiac involvement limiting the utility of biopsy and the available clinical criteria have limited diagnostic accuracy. Multimodality imaging plays a large role in the diagnosis and management of patients with cardiac sarcoidosis with the different imaging modalities offering complimentary information and functions. 

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Quoatables

“It’s not important for you to love the Soviet Union. It’s important for the Soviet Union to love you back [Stalin regarding the famous dissonant Russian poet Anna Akhmatova]. When we talk about PET, you love PET, but the PET has to love you back, and it has to love you back in a way where you have to know how to approach this test. With, first, some humility about its limitations: 1) inflammation is universal...and 2) the prep is extremely important.”  -- 11:25

“A test without a good preparation is a preparation to fail.” --15:30

“Sarcoidosis is kind of the tuberculosis that we have in medicine—it can present as anything.” --36:40

Pearls

Cardiac Magnetic Resonance Imaging (Cardiac MRI) and/or 18-Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) are complimentary tests in the evaluation of cardiac sarcoidosis. Both tests look for scarring and inflammation. Cardiac MRI is a good initial test due to its high negative predictive value (i.e. absence of LGE makes cardiac sarcoidosis less likely) but not great for following a cardiac sarcoidosis patient’s response to therapy. Cardiac FDG-PET is great to follow a patient's response to therapy especially in patients with intracardiac devices such as a pacemaker.

18-fluorodeoxyglucose (FDG) is a glucose analog and just like glucose, is transported into the cell by transporters. Once in the cell, it is phosphorylated, like glucose is, by hexokinase in preparation for use in glycolysis. Unlike glucose, however, it does not proceed to be metabolized any further in the glycolysis pathway and remains trapped in the cell. In the inflammatory cells within sarcoid granulomas, glycolysis is significantly increased to fuel the large energy requirement. Thus, these inflammatory cells (i.e. macrophages) can take up large amounts of FDG.

When planning to obtain a cardiac FDG-PET for evaluation of cardiac sarcoidosis, patient preparation is key! There are several available dietary protocols to accomplish the goal of switching the patient’s metabolism to be reliant on fatty acids instead of glucose as an energy source. One such protocol used by the discussants in the episode is prolonged fasting (10-12 hours) prior to the study preceded by two meals that are high in fat and proteins and low in carbohydrates—a ketogenic diet. By having the patient eat this diet, we are trying to switch the metabolism because there is no ability or no offer ...