Incidental Detection of NSTEMI on Whole-body [¹⁸F] FDG PET/CT

An 81-year-old diabetic woman with a history of polymyalgia rheumatica and elevated inflammatory markers, underwent whole-body [¹⁸F] Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scan to rule out vasculitis.[123456] There was no uptake in the vessel walls, but incidental increased myocardial uptake in the lateral wall of the left ventricle (A [maximum intensity projection – image], B [axial PET], D [axial PET/CT fusion], E [cardiac reconstruction PET image], and F [polar plot]) with corresponding reduced contrast enhancement on the CT (C) [Figure 1]. During the PET/CT study, the patient suffered from chest pain and was referred to the emergency department, where non-ST segment elevation myocardial infarction (NSTEMI) was confirmed with elevated high-sensitive troponin, electrocardiogram, and echocardiography (lateral wall hypokinesia). Subsequently performed coronary angiography (G) showed a coronary three-vessel disease with high-grade stenosis of the proximal left circumflex artery and the first obtuse marginal branch. Successful revascularization with stenting was performed (H). In addition, a small progressive FDG-avid nodule (A, I, J) was detected in the upper lobe of the right lung, suspicious for lung cancer, along with emphysema, which is under evaluation and further follow-up.

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Figure 1 Maximum-intensity projection image (a) of whole-body [¹⁸F] Fluorodeoxyglucos positron emission tomography/computed tomography (PET/CT) scan showed absence of large vessel vasculitis but depicted incidental cardiac uptake (short arrow) and a small nodule in the upper lobe of the right lung (long arrow). Axial PET/CT views (b and d) and cardiac reconstruction PET image (e) and the polar plot (f) show increased uptake in the lateral wall of the left ventricular myocardium with corresponding reduced contrast enhancement on the CT (c). Coronary angiography (g) showed three-vessel disease with high-grade stenosis of the proximal left circumflex artery and the first obtuse marginal branch, which was successfully revascularized with stenting (h). Metabolically active small nodule in the right lung on axial views (i and j) suspicious for neoplastic etiology

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Increased FDG uptake in areas with reduced blood flow is suggestive of either viable/hibernating myocardium or acute ischemia that can be reversed by timely revascularization to prevent scar formation and preserve left ventricular function.[78910] The hibernating myocardium refers to the resting Left Ventricular (LV) dysfunction, but with the presence of viable myocytes, due to chronically reduced coronary blood flow (ischemia). The biopsy of hibernating myocardium has shown to contain enlarged extracellular spaces with cellular debris, macrophages, fibroblasts, and collagen fibrils, associated with basement membrane thickening.[11] Although the patient had not undergone the typical patient preparation for myocardial viability assessment (overnight prolonged fasting and high-fat and low-carbohydrate diet and heparin to suppress physiological myocardial uptake), the viable/hibernating myocardium was clearly detectable and the physiological uptake was efficiently suppressed. Interestingly, this particular patient had no previous history of chronic myocardial ischemia and was not a known case of coronary artery disease. The lateral wall myocardial uptake was more likely related to acute inflammation secondary to acute ischemia or evolving infarction. Macrophages infiltrate the infarction zone within 24 h and primarily secrete pro-inflammatory cytokines and matrix proteases to clear dying cell debris.[12] [¹⁸F]-FDG is a useful tracer for imaging macrophages and early inflammatory cellular changes. An evolving NSTEMI, which the patient probably developed just around the period of the scan procedure, was detected in time and managed successfully. This case highlights the importance of careful evaluation of whole-body PET/CT images-before discharging the patient-for incidental findings, sometimes representing potentially life-threatening emergencies.