The following are key points to remember from a state-of-the-art review on cardiac sarcoidosis (CS) phenotypes, diagnosis, treatment, and prognosis:

1. Phenotype for CS varies from being diagnosed postmortem or via magnetic resonance imaging (MRI) with no or minimal symptoms to clinically manifest sarcoid. Clinically isolated CS is more serious than CS appearing with extracardiac disease. The most common clinical signs for CS are high-grade atrioventricular block, ventricular arrhythmias, and heart failure.
2. In pre-existing sarcoidosis, elevated troponins, B-type natriuretic peptide (BNP), anti-heart, and anti-intercalated disk antibodies support CS diagnosis. Echo strain imaging and electrocardiography (ECG) may be normal in CS. Computed tomography of the chest can suggest intrathoracic sarcoidosis, but diagnosis relies on cardiac MRI and/or ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET).
3. Cardiac FDG-PET is combined with whole body imaging to assess extracardiac involvement. The study needs a low carbohydrate/high fat diet followed by fasting. A hot spot on FDG-PET overlapping a perfusion defect is characteristic of CS. Hibernating myocardium, myocarditis, and genetic cardiomyopathies may cause abnormal FDG-PET uptake.
4. FDG-PET scans can help identify response to treatment. Right ventricular (RV) uptake and FDG uptake overlapping a perfusion defect portend poorer prognosis.
5. Delayed post contrast imaging on cardiac MRI is key for CS. Late gadolinium enhancement (LGE) is typically patchy, in a nonischemic pattern. A hook sign of the septal LGE continuing into the RV free wall is characteristic of CS but can also be seen in giant cell myocarditis.
6. For histological proof, guidelines recommend extracardiac over endomyocardial biopsy (EMBx). Targeted EMBx using imaging or intracardiac voltage mapping increases its sensitivity. Histo-pathological findings include non-necrotic granulomas with isolated giant cells when other causes are excluded.
7. Guidelines recommend CS screening in patients with known extracardiac sarcoidosis with symptom assessment, ECG, and echo. Cardiac MRI and FDG-PET are recommended if these studies are abnormal.
8. Initial CS treatment is comprised of steroids (usually prednisone 0.5 mg/kg/day). Prednisone is tapered down every 4 weeks in decrements of 5-10 mg until a dose of 10 mg/day is achieved. Authors recommend steroid discontinuation after 12-16 months of treatment if there are no signs of disease activity with serial annual follow-up for 5 years followed by alternate year follow-up visits.
9. Efficacy of treatment is checked with symptom assessment, ECG, arrhythmia burden, cardiac biomarkers, and left ventricular ejection fraction (LVEF). The authors recommend serial FDG-PET only if there is a discrepancy between clinical observations or if relapse or treatment failure is suspected.
10. The authors recommend a second immunosuppressant (methotrexate, cellcept, azathioprine, leflunomide, and cyclophosphamide) when either steroids fail or there is a need to reduce steroid toxicity risk or with rapidly progressive heart failure, life-threatening arrhythmias, or extensive inflammation on imaging. Methotrexate is most commonly used but the authors prefer azathioprine 1-2 mg/kg weight with close follow-up for side effects.
11. When all therapies fail, biological anti–tumor necrosis factor agents like infliximab may help. These agents need comprehensive screening for tuberculosis and vaccination. Authors use infliximab 5 mg/kg at weeks 0, 2, and 4 weeks and then every 8th week for 1 year or until inflammation subsides.
12. For symptomatic ventricular arrhythmias, the effect of immunosuppression is not well established. If inflammation is detected, steroids are recommended with antiarrhythmics. If medical therapy fails, catheter ablation can be considered.
13. Clinically manifest CS has a 10% risk for sudden cardiac death over 5-year follow-up. North American guidelines recommend implantable cardioverter-defibrillator for LVEF <35%, CS with history of syncope, if there is significant scarring on imaging, or EF >35% with indication for pacemaker.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging

Keywords: Arrhythmias, Cardiac, Cardiomyopathies, Contrast Media, Defibrillators, Implantable, Electrocardiography, Echocardiography, Fluorodeoxyglucose F18, Gadolinium, Heart Failure, Immunosuppressive Agents, Inflammation, Magnetic Resonance Imaging, Myocarditis, Myocardium, Natriuretic Peptide, Brain, Pacemaker, Artificial, Perfusion Imaging, Phenotype, Sarcoidosis, Steroids, Stroke Volume, Syncope, Tomography, Troponin

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