Version May 2024
INTRODUCTION — The clinical presentation of cardiac sarcoidosis (CS) ranges from an incidentally discovered condition to heart failure (HF), brady- and tachyarrhythmias, and sudden death.
The diagnosis of CS is difficult to establish, and as a result, CS is often underrecognized in clinical practice [1]. CS most often occurs as a manifestation of systemic sarcoidosis, although isolated CS can occur in patients who do not have evidence of sarcoidosis in other organs [2]. Yet, commonly used clinical criteria require the diagnosis of extracardiac disease in order to establish the diagnosis of CS in the absence of having a positive endomyocardial biopsy. While endomyocardial biopsy provides a high specificity for diagnosing CS, this invasive test has a limited sensitivity. Furthermore, there is limited understanding of disease progression and a lack of consensus on the optimal methods for disease detection.
This topic will discuss the clinical manifestations of CS and provide an overview of how to evaluate patients with suspected CS. Management and prognosis of CS and diagnosis and management of systemic sarcoidosis are discussed separately. (See "Management and prognosis of cardiac sarcoidosis" and "Clinical manifestations and diagnosis of sarcoidosis" and "Overview of extrapulmonary manifestations of sarcoidosis" and "Pathology and pathogenesis of sarcoidosis" and "Treatment of pulmonary sarcoidosis: Initial approach" and "Treatment of pulmonary sarcoidosis refractory to initial therapy".)
PREVALENCE — Clinically manifest CS has been estimated as occurring in approximately 5 percent of patients with pulmonary/systemic sarcoidosis [3]. However, the true prevalence of CS is uncertain and is likely underestimated since many individuals with CS have nonspecific symptoms or subclinical disease. Autopsy and imaging studies of patients with systemic sarcoidosis have identified evidence of CS in 20 to 29 percent in the United States and as high as 58 to 70 percent in Japan [3-6]. In the United States, 13 to 25 percent of deaths from sarcoidosis have been attributed to CS, while in Japan, 47 to 85 percent of deaths from sarcoidosis have been attributed to cardiac involvement [7].
The risk of adverse cardiac outcomes in patients with systemic sarcoidosis was illustrated by a study of data from Danish nationwide registries in which 11,834 patients diagnosed with sarcoidosis during 1996 to 2016 (and without heart failure or arrhythmias at baseline) were matched by age, sex, and comorbidities with 47,336 individuals in the population without sarcoidosis [8,9]. Patients with sarcoidosis had higher 10-year risk of heart failure compared with the background population (3.18 versus 1.72 percent) as well as other adverse cardiac events including a composite of ICD implantation, ventricular arrhythmias, and cardiac arrest (0.96 versus 0.45 percent), a composite of pacemaker implantation, atrioventricular block, and sinoatrial dysfunction (0.94 versus 0.51 percent), and atrial fibrillation or flutter (3.44 for sarcoidosis patients versus 2.66 percent). The 10-year risk of mortality was also higher for sarcoidosis patients (10.88 versus 7.43 percent).
CS can affect patients of all racial backgrounds and ages, with an average age at presentation of approximately 50 years old [10].
Isolated CS may occur in up to 25 percent of CS cases, and thus the absence of extracardiac sarcoidosis does not rule out CS [2,11].
Several reports have suggested that the incidence of CS may be increasing [10]; however, it is unclear if such an increase is due to a true increase in the prevalence of disease or to increased awareness and detection of this condition.
The prevalence of pulmonary sarcoidosis is discussed separately. (See "Clinical manifestations and diagnosis of sarcoidosis", section on 'Epidemiology'.)
PATHOGENESIS — Sarcoidosis is a heterogeneous disorder of unknown etiology whose signature lesions are noncaseating granulomata. Sarcoidosis may involve any part of the heart. While the ventricular myocardium is most commonly affected, involvement by the atria, papillary muscles, valves, coronary arteries, and pericardium has been described. Similar to other involved organs, cardiac disease generally progresses from areas of focal inflammation to scar. However, the natural history of CS is not well characterized and is highly variable. Some individuals may only have a small area of inflammation or scar and will not experience any significant clinical sequelae. On the other hand, some patients will progress to develop a pattern of extensive inflammation and scar. Given the limited data on how this disease progresses, it may be preferable to refer to different patterns of CS rather than stages, as use of stages implies a linear progression across different stages.
CLINICAL MANIFESTATIONS — The most frequent clinical manifestations of CS are atrioventricular (AV) block, arrhythmias, HF, and sudden cardiac death [10,12].
Symptoms and signs — Symptoms and signs of CS include palpitations, presyncope, syncope, fatigue, dyspnea, orthopnea, and sudden cardiac death. Palpitations may be caused by either supraventricular or ventricular arrhythmias. Presyncope or syncope can be caused by AV block, ventricular tachycardia, or supraventricular tachycardia. Fatigue, dyspnea, and orthopnea can reflect HF caused by CS. However, fatigue and dyspnea are nonspecific symptoms that may also result from lung disease in patients with pulmonary sarcoidosis.
By contrast, angina symptoms are generally considered more suggestive of atherosclerotic coronary artery disease (CAD), as CS less frequently causes angina. (See 'Coronary artery disease' below.)
Key manifestations — The key clinical manifestations of CS are conduction system disease, tachyarrhythmias, cardiomyopathy, HF, and rarely CAD.
Arrhythmias
Conduction system disease — AV block is the most common clinical presentation in patients with clinically evident CS. In a retrospective study of 110 patients with histologically confirmed CS, symptomatic heart block was present in 44 percent of patients [10,13]. Complete AV block occurs at a younger age in patients with CS than in individuals with complete AV block due to other etiologies [14]. Prolongation of the PR interval (first-degree AV block) due to disease of the AV node or bundle of His and intraventricular conduction defects are common [15] and may progress. Thus, conduction system disease may initially be silent and then progress to complete AV block [16] and cause syncope or even sudden death [17]. (See "Etiology of atrioventricular block" and "Third-degree (complete) atrioventricular block".)
Tachyarrhythmias — Supraventricular and ventricular tachyarrhythmias are both common in CS.
Ventricular arrhythmias (sustained or nonsustained ventricular tachycardia and ventricular premature beats [VPBs]) are the second most common clinical presentation of CS, occurring in approximately 30 percent of cases [10]. These arise when sarcoid granulomas within the myocardium become foci for abnormal automaticity, or may disrupt ventricular activation and recovery, causing re-entrant arrhythmias. Scar within the myocardium may also cause re-entrant arrhythmias.
Supraventricular arrhythmias are a rare presenting feature at the diagnosis of cardiac sarcoidosis but can develop at any time in the clinical course [18]. Supraventricular arrhythmias seen with CS include paroxysmal atrial tachycardia, atrial flutter, atrial fibrillation, and sinus arrest secondary to granulomatous involvement of the sinus node. In a retrospective study that included 100 patients with definite or probable CS, the prevalence of supraventricular arrhythmias over a mean follow-up of 5.8 years was 32 percent, with atrial fibrillation being the most common arrhythmia [19]. The presence of left atrial enlargement by echocardiography was most strongly associated with the development of supraventricular arrhythmias. A high prevalence of atrial arrhythmias in CS was also observed in a study evaluating 135 patients who had ambulatory electrocardiography (ECG) monitoring; patients with systemic sarcoidosis who had late gadolinium enhancement by cardiac magnetic resonance imaging had a threefold increase in the prevalence of atrial arrhythmias compared with those who did not have any evidence of cardiac involvement (36 versus 12 percent) [20].
Sudden cardiac death — Sudden death due to ventricular tachyarrhythmias or conduction block accounts for 25 to 65 percent of deaths caused by CS [7,21-24]. Some patients with known systemic sarcoidosis develop symptomatic or electrocardiographically evident arrhythmias or conduction abnormalities prior to sarcoid-related sudden death, assisting diagnosis and therapeutic management. However, sudden death can occur in the absence of symptoms or a previous cardiac event [25,26]. In a large CS case series, fatal and aborted sudden cardiac death was the presenting manifestation in 14 percent of CS cases [24]. Thus, a key diagnostic challenge is to identify individuals at risk for sudden death to enable preventive therapies. (See "Pathophysiology and etiology of sudden cardiac arrest" and "Management and prognosis of cardiac sarcoidosis", section on 'Management of arrhythmias and conduction system disease'.)
Cardiomyopathy and heart failure — Presence of cardiomyopathy or HF in a patient with known extracardiac sarcoidosis should prompt an evaluation for CS. Patients with sarcoidosis are at increased risk of developing HF [8,27]. HF is less common than arrhythmia at initial presentation and is the first clinical manifestation of CS in fewer than 20 percent of cases. However, CS may even be diagnosed after transplant in the explanted hearts of patients thought to have an idiopathic cardiomyopathy.
CS is a cause of cardiomyopathy, which may manifest with symptoms and signs of HF (eg, orthopnea, edema). CS can cause an arrhythmogenic cardiomyopathy with heart block, supraventricular and ventricular arrhythmia, a dilated cardiomyopathy (with dilated left ventricular [LV] volumes and depressed LV ejection fraction [LVEF], which can lead to HF with reduced ejection fraction), or a restrictive cardiomyopathy (with normal LV volumes and preserved LVEF), which can lead to HF with preserved ejection fraction.
Fewer data are available on the prevalence and clinical significance of right ventricular (RV) dysfunction attributable to CS [28-30]. Some patients with CS present with signs of predominantly right-sided HF, which can be caused by sarcoid-related inflammation or scar affecting the RV [31] or less commonly secondary to CS involving the tricuspid valve [32]. Right HF due to CS involving the RV should be distinguished from other causes of right HF including pulmonary hypertension secondary to lung disease. (See 'Differential diagnosis' below.)
Coronary artery disease — Sarcoidosis can involve the coronary arteries with a vasculitis, which has been reported as a rare cause of unstable angina or myocardial infarction [33-35]. A case report described spontaneous coronary artery dissection in a patient with CS [36]. However, patients with CS are more likely to have other, more typical types of CAD.
As discussed below, CS should be distinguished from ischemic heart disease in patients with symptoms consistent with both disorders. However, it is important to acknowledge that CS and atherosclerotic CAD often coexist. Data are lacking on the frequency of CAD in patients with CS. (See 'Differential diagnosis' below.)
Test findings — Preliminary test findings may raise clinical suspicion of CS but are not specific for CS.
ECG findings in patients with CS include PR interval prolongation, second- or third-degree AV block, QRS prolongation (with or without right bundle branch block or left bundle branch block), frequent VPBs, atrial arrhythmias, pathologic Q waves, and nonspecific ST segment and T wave abnormalities. However, none of these features are specific for CS. The 12-lead ECG has low sensitivity (generally reported as <50 percent) for detection of CS [17,37].
A chest radiograph is not required to diagnose CS, but it is a component of the diagnosis of pulmonary sarcoidosis. Findings suggestive of HF include cardiomegaly, cephalization of the pulmonary vessels, Kerley B-lines, and pleural effusions. However, these findings are not specific for CS, and absence of these findings does not exclude CS. (See "Heart failure: Clinical manifestations and diagnosis in adults", section on 'Chest radiograph'.)
Chest radiographic findings in patients with pulmonary sarcoidosis are discussed separately. (See "Clinical manifestations and diagnosis of sarcoidosis", section on 'Chest radiograph'.)
Elevated levels of cardiac troponin, serum angiotensin converting enzyme, serum lysozyme, and urinary calcium have been reported in patients with CS. As an example, in a study of 62 patients presenting with CS, high-sensitivity cardiac troponin T or I was elevated at presentation in 26 of 50 (52 percent) patients in which it was measured [38]. While an incidental finding of an elevated cardiac troponin may prompt evaluation for myocardial disease, these biomarkers do not have a role in screening for CS or in assigning diagnostic probability.
DIAGNOSIS — The diagnosis of CS requires appropriate clinical suspicion and often requires integrating clinical and pathologic data together with the results of advanced cardiac imaging.
When to consider cardiac sarcoidosis — The diagnosis of CS should be considered in the following patients [39-41]:
●Patients with histologic or clinical diagnosis of extracardiac sarcoidosis, with or without cardiac symptoms, should be evaluated for subclinical, as well as clinical, cardiac involvement (arrhythmias, conduction disease, HF, etc). (See "Clinical manifestations and diagnosis of sarcoidosis".)
●Adults (age <60 years) with unexplained syncope or unexplained new onset conduction system disease such as sustained second- or third-degree AV block. (See "Second-degree atrioventricular block: Mobitz type II" and "Third-degree (complete) atrioventricular block" and "Etiology of atrioventricular block".)
●Patients with aborted sudden cardiac death or sustained ventricular tachycardia (VT) not explained by typical outflow tract VT, fascicular VT, or VT due to other structural heart disease such as coronary artery disease (CAD).
●In patients with unexplained dilated, restrictive, or arrhythmogenic cardiomyopathy. (See "Determining the etiology and severity of heart failure or cardiomyopathy" and "Definition and classification of the cardiomyopathies" and "Causes of dilated cardiomyopathy".)
Approach to diagnosis — The following approach to the diagnosis of CS is similar to, but different from, the approach described in the 2014 Heart Rhythm Society (HRS) expert consensus statement [42]:
●Perform a detailed history and physical along with a 12-lead ECG. (See 'Initial evaluation and testing' below.)
•Patients with indications for echocardiography or continuous ambulatory ECG (Holter) monitor should undergo both of these tests. The authors do not recommend these tests for routine screening, but some experts suggest routine use of echocardiography [42] and Holter monitoring to evaluate patients with extracardiac sarcoidosis. (See 'Holter monitoring' below and 'Echocardiography' below.)
●Based upon presence of specific symptoms, ECG findings, and/or echocardiographic abnormalities, identify candidates for advanced cardiac imaging. (See 'Criteria for advanced cardiac imaging' below.)
•Patients who do not meet criteria for advanced cardiac imaging require no further immediate evaluation for CS. For patients with extracardiac sarcoidosis, we recommend serial (eg, yearly) clinical reevaluation with ECG to detect development of symptoms and signs of CS.
●For patients with criteria for advanced imaging, proceed with advanced imaging (cardiovascular magnetic resonance [CMR] and/or 18F-fluorodeoxyglucose-positron emission tomography [FDG-PET]) based upon local availability and expertise and test results. (See 'Selection of advanced imaging' below.)
●If the patient lacks histologic confirmation of sarcoidosis, the feasibility of extracardiac or endomyocardial biopsy (EMB) should be assessed. (See 'Role of biopsy' below.)
●Integrate all clinical data and apply diagnostic criteria to identify definite and probable CS. (See 'How to diagnose cardiac sarcoidosis' below.)
●Among patients with uncertain diagnosis, determine need for and feasibility of further diagnostic evaluation, including EMB. (See 'Role of biopsy' below.)
Initial evaluation and testing — Patients who have biopsy-proven or clinically diagnosed extracardiac sarcoidosis should undergo evaluation for symptoms and signs of cardiac involvement and an ECG.
The following symptoms and signs should prompt initial testing with a continuous ambulatory ECG (Holter) monitor and an echocardiogram (see 'Holter monitoring' below and 'Echocardiography' below). Triggers for initial testing include symptoms such as palpitation, syncope, atypical chest pain, dyspnea, effort intolerance, or physical exam signs such as jugular venous distension, cardiac murmur, S3 or S4 gallop, displaced point of maximal impulse, or unexplained HF. Clinical presentation may be subtle and present with features of arrhythmogenic, dilated, or even restrictive cardiomyopathy. (See "Heart failure: Clinical manifestations and diagnosis in adults" and "Determining the etiology and severity of heart failure or cardiomyopathy".)
The authors do not recommend echocardiography for routine screening for CS, but some experts (including the HRS Expert Consensus Statement) suggest echocardiography to evaluate patients with extracardiac sarcoidosis [42], and some experts also suggest continuous ambulatory (Holter) monitoring in such patients.
Criteria for advanced cardiac imaging — We recommend advanced cardiac imaging (CMR imaging or FDG-PET) for selected patients with or without evidence of extracardiac sarcoidosis.
With extracardiac sarcoidosis — The criteria listed here for patients with histologic or clinical evidence of extracardiac sarcoidosis are modified from criteria for patients with histologic evidence of extracardiac sarcoidosis in the 2014 HRS Expert Consensus Statement [42]:
●Patients who have biopsy-proven or clinically diagnosed extracardiac sarcoidosis and one of the following symptoms or signs consistent with (but not specific for) CS [42]:
•One or more of the following symptoms: prominent palpitations lasting >1 to 2 weeks, presyncope, or syncope.
•One or more of the following ECG abnormalities: complete left or right bundle branch block; presence of unexplained pathologic Q waves in two or more leads; sustained first-, second-, or third-degree AV block; or sustained or nonsustained VT.
•One or more of the following echocardiographic abnormalities: regional wall motion abnormality, ventricular aneurysm, basal septal thinning, or depressed LVEF. The authors use an LVEF threshold of <50 percent; some experts use an LVEF threshold of <40 percent as described in the consensus statement [42].
Without extracardiac sarcoidosis — Patients with no prior history of extracardiac sarcoidosis who have one or more of the following conditions are candidates for advanced cardiac imaging:
●Unexplained second-degree Mobitz type II or third-degree AV block in adults aged <60 years.
●Sustained monomorphic VT in the absence of any known etiology. This criterion was favored by the majority of the 2014 HRS Expert Consensus Statement writing group but was not included as a formal recommendation [42].
Patients without criteria for advanced cardiac imaging — Patients who lack any of the symptoms or signs that serve as indications for advanced cardiac imaging are unlikely to benefit from further immediate evaluation. In one study of 62 patients with extracardiac sarcoidosis, the presence of at least one cardiac symptom, ECG abnormality, Holter monitor finding, or echocardiographic finding was highly sensitive for CS (100 percent, 95% CI 88-100 percent) [43]. Thus, the probability of CS is low in patients without any criteria for advanced imaging, so further immediate cardiac evaluation is not indicated. Patients with extracardiac sarcoidosis without current symptoms and signs of CS should be followed prospectively with serial (eg, annual) clinical exams and ECG to monitor for potential development of signs and symptoms of CS.
Selection of advanced imaging — The choice between CMR, FDG-PET, or both among patients with suspected CS with an indication for advanced imaging is based upon test characteristics, feasibility, and test results.
●CMR
•For patients with suspected CS with an indication for advanced cardiac imaging, we recommend CMR imaging with gadolinium-based contrast as the initial diagnostic testing option, unless there are contraindications for performing this test. A similar recommendation on CMR as the preferred initial test has also been made by the American Thoracic Society clinical practice guideline on diagnosis and detection of sarcoidosis [44] and by a joint multi-society European position statement [45]. (See 'Cardiovascular magnetic resonance' below.)
•For patients with indeterminate FDG-PET results, we recommend performing CMR after FDG-PET.
●FDG-PET
•If CMR cannot be performed (due to conditions such as renal dysfunction, which is a contraindication for gadolinium-based contrast or presence of an incompatible device), proceed with FDG-PET study as the alternative initial diagnostic test.
•We also recommend FDG-PET after CMR in the following clinical settings:
-If CMR is negative and high clinical suspicion for CS persists. As an example, FDG-PET is suggested for a patient with known extracardiac sarcoidosis and typical signs and/or symptoms of CS as described above (see 'Criteria for advanced cardiac imaging' above) with negative CMR.
-If CMR is inconclusive due to image quality or nonspecific findings (eg, midwall late gadolinium enhancement [LGE] in a pattern consistent with myocarditis or sarcoidosis, or RV involvement in a pattern that is consistent with arrhythmogenic RV cardiomyopathy or sarcoidosis).
-CMR is strongly suggestive of CS, and a decision is made to treat the patient with immunosuppressive therapy, as described next. (See "Management and prognosis of cardiac sarcoidosis", section on 'Identification of inflammation'.)
•We recommend performing FDG-PET in patients who are candidates for immunosuppressive therapy for CS. In this setting, FDG-PET would be useful for the following reasons: the presence of myocardial as well as extracardiac inflammation would indicate a greater role for systemic immunosuppressive therapy, and the FDG-PET scan could serve as a baseline upon which to compare future FDG-PET studies to determine response to therapy.
Role of biopsy — Since pathologic confirmation (even if extracardiac) provides the most definitive means of identifying CS, efforts should be made to safely obtain a suitable tissue sample in patients with suspected CS who lack histologic confirmation. Biopsy of extracardiac sites may provide a higher yield (greater sensitivity) and lower procedural risk than EMB (which has a sensitivity of approximately 20 to 30 percent). (See "Endomyocardial biopsy", section on 'Late AV block, arrhythmias, or refractory HF'.)
For patients with criteria for advanced imaging for CS, we suggest limited whole-body FDG imaging in addition to dedicated cardiac imaging for CS. Such information may be useful for the following reasons: to enhance diagnostic certainty since patients with cardiac findings who have FDG-avid extracardiac involvement in a pattern consistent with sarcoidosis are more likely to have CS, to identify FDG-avid lymph nodes or lung tissue for biopsy that may be higher yield than a cardiac biopsy for establishing a tissue diagnosis, and to obtain data on the presence and severity of extracardiac disease activity (ie, amount of inflammation outside the heart), which may be relevant for decisions on the role of immunosuppressive therapies. The field of view for whole-body imaging should range from the orbits to the upper thigh, and at minimum should include the chest, liver, and spleen, as these are the most frequently affected organs.
In cases of isolated CS or a negative extracardiac biopsy, EMB is required for definitive diagnosis.
However, even when biopsy examination does not reveal noncaseating granulomas, as described above, some patients may still have a sufficiently high probability of having CS (see 'Probable cardiac sarcoidosis' below) or may have another inflammatory cardiomyopathy for which treatment with immunosuppressive therapy would be warranted, especially patients who are symptomatic, have electrical instability, or who have new LV dysfunction along with findings on FDG-PET imaging consistent with active inflammation. (See 'Endomyocardial biopsy' below and "Clinical manifestations and diagnosis of myocarditis in adults", section on 'Diagnosis'.)
How to diagnose cardiac sarcoidosis — Data from the diagnostic evaluation as described above are integrated to determine the likelihood of CS based on the following diagnostic categories. Data synthesis should include review of advanced cardiac imaging with cardiovascular imaging experts with knowledge and expertise in the use of FDG-PET and CMR for diagnosis of CS.
Definite cardiac sarcoidosis — A definite diagnosis of CS is established by detection of noncaseating granuloma on histologic examination of myocardial tissue with no alternative cause identified [42]. Since the histologic findings are not pathognomonic, some experts consider the diagnosis of CS "highly probable" if myocardial noncaseating granulomas are detected. [46,47]. Thus, a definite diagnosis of CS is confirmed only if an EMB or other myocardial tissue specimen is available, shows diagnostic findings, and other causes have been excluded.
Uncertain diagnosis — The diagnosis of CS is frequently uncertain. The following categories (highly probable, probable, and possible CS) may be used in cases in which there is uncertainty regarding the diagnosis of CS. This classification system, while not widely used for evaluating the likelihood of CS, has been developed based on the World Association of Sarcoidosis and Other Granulomatous Diseases (WASOG) organ assessment instrument, which has been used to determine the probability of sarcoidosis organ involvement [48]. Management with immune suppression or a prophylactic implantable cardioverter-defibrillator (ICD) is typically restricted to patients with probable or definite CS. (See "Management and prognosis of cardiac sarcoidosis", section on 'Approach to management'.)
Clinical findings suggesting cardiac sarcoidosis — For patients with uncertain diagnosis of CS, the presence of one or more of these clinical findings suggests a higher likelihood of CS [42].
●Unexplained reduced LVEF (<40 percent)
●Unexplained sustained VT (spontaneous or induced)
●AV block: Mobitz type II second degree or third degree (whether or not responsive to immunosuppressive therapy)
Probable cardiac sarcoidosis — The term probable CS denotes a likelihood of CS ≥50 percent. This term recognizes the inherent uncertainty that is often clinically present when evaluating patients with suspected CS. While the HRS consensus statement represents the most contemporary and comprehensive classification system to date, it has a few limitations [42]. First, the criteria categorize CMR and PET results in a binary fashion, yet these tests provide a spectrum of findings. Second, the HRS criteria require a histologic diagnosis of extracardiac sarcoidosis for diagnosis of probable CS.
Noninvasive criteria for "highly probable" (>90 percent likelihood) CS have not been established. The authors apply this term to cases with histologic or clinical diagnosis of extracardiac sarcoidosis, clinical findings suggesting CS, and imaging findings by CMR or FDG-PET typical for CS, when other potential causes for these findings have been excluded.
With histologic confirmation of extracardiac sarcoidosis — When there is confirmation of extracardiac sarcoidosis, we use the criteria for probable CS included in the HRS Expert Consensus Statement [42]:
●Histologic diagnosis of extracardiac sarcoidosis (with no histologic evidence from myocardial tissues).
AND
●One or more of the following cardiac findings:
•A clinical finding suggesting CS. (See 'Clinical findings suggesting cardiac sarcoidosis' above.)
•Any of the following imaging findings typical for CS:
-Cardiac FDG-PET with patchy uptake in a pattern consistent with CS.
-CMR with LGE in a pattern consistent with CS.
OR
-Cardiac 67gallium diffuse uptake by the heart. However, cardiac gallium scans are no longer performed in most institutions as FDG-PET offers improved diagnostic accuracy.
AND
●Other causes of the cardiac manifestation(s) have been reasonably excluded.
Without histologic confirmation of extracardiac disease — A major difficulty in identifying patients with isolated CS is the lack of specificity of symptoms, signs, and imaging findings of CS. Thus, patients with clinical findings and/or imaging findings suggestive of CS without extracardiac sarcoidosis remain in a grey area of diagnostic and prognostic uncertainty. The HRS consensus statement does not include criteria for probable CS in patients without histologic diagnosis of extracardiac sarcoidosis [2]. The authors diagnose "probable CS" in selected patients without histologic confirmation of extracardiac disease who have clinical findings suggesting CS and both CMR and FDG-PET findings typical for CS, when other potential causes for these findings have been excluded via a comprehensive evaluation. Other experts diagnose isolated CS only in patients with myocardial histologic confirmation [2].
The diagnostic accuracy of advanced imaging was assessed in 42 patients who were studied by CMR (31) and/or FDG-PET (18) prior to cardiac transplantation [49]. Histological assessment of the explanted heart was used as the reference standard.
●FDG-PET: For probable or highly probable FDG-PET findings for CS, the sensitivity was 100 percent (95% CI 54.1-100 percent) and the specificity was 33.3 percent (95% CI 9.9-65.1 percent). For highly probable FDG-PET, the sensitivity was 83.3 percent (95% CI 35.9-99.6 percent) and the specificity was 100 percent (95% CI 73.5-100 percent).
●CMR: Data were limited for CMR as only one patient studied by CMR was subsequently found to have CS. The specificity of probable or highly probable CMR findings for CS was 76.7 percent (95% CI 57.7-90.1 percent). The specificity of highly probable CMR was 90 percent (95% CI 73.5-97.9 percent).The evaluation of etiology of cardiomyopathy is discussed separately. (See "Determining the etiology and severity of heart failure or cardiomyopathy".)
Unresolved cases — For patients with or without extracardiac sarcoidosis who have a clinical symptom or sign suggestive of CS but lack criteria for definite or probable CS, the likelihood of CS is generally <50 percent, and other alternative diagnoses are more likely to explain the patient’s symptoms. Treatment for CS is not indicated for patients in this category, although serial (eg, annually or twice yearly) follow-up may be appropriate for some patients.
Management of patients with extracardiac sarcoidosis with no or minor cardiac signs or symptoms is discussed above. (See 'Patients without criteria for advanced cardiac imaging' above.)
Comparison of major society guidelines — The most commonly used clinical criteria for diagnosing CS are the revised Japanese Ministry of Health and Welfare (JMHW) criteria [39] and the HRS Expert Consensus Statement [42]. Both guidelines provide a histologic pathway whereby a definitive diagnosis of CS can be established by an EMB, which reveals noncaseating granulomas. In patients who do not have a positive EMB, these criteria require a diagnosis of extracardiac sarcoidosis (for the JMHW, this can be either clinical or histologic, while for the HRS criteria, histologic diagnosis of extracardiac sarcoidosis is required) in conjunction with other criteria.
The most comprehensive document on the role of cardiac PET for detecting CS and using the results for making treatment decisions as well as following the response to therapy has been published as a joint consensus document from the Society of Nuclear Medicine and Molecular Imaging and the American Society of Nuclear Cardiology. This document provides an overview of the indications for cardiac PET, as well as specific details relating to image acquisition and patient preparation [50]. The American Thoracic Society's clinical practice guideline on diagnosis and detection of sarcoidosis also provides information on the role of various diagnostic tests for evaluating patients with suspected sarcoidosis [44].
Key diagnostic tests
Holter monitoring — Continuous ambulatory ECG (Holter) monitoring for 24 hours or more in patients with CS may identify a high burden of ventricular premature beats, nonsustained or sustained VT, AV block, or atrial arrhythmias. Among the commonly used screening tests, ambulatory monitoring has the highest sensitivity (eg, 89 percent), but it has low specificity (21 percent) [51].
Echocardiography
Echocardiographic findings — Echocardiographic findings in patients with CS are variable and may include focal areas of edema resulting in increased wall thickness and mimicking hypertrophic cardiomyopathy (eg, asymmetric septal hypertrophy [52]) or in more advanced patterns of involvement, focal areas of akinesis or dyskinesis, wall thinning, or aneurysm mimicking arrhythmogenic RV cardiomyopathy.
Among patients with CS, LVEF can be either preserved or reduced. Patients with a dilated cardiomyopathy have dilated LV chambers and depressed LVEF [53]. Patients with a restrictive cardiomyopathy have normal LV chamber sizes and LVEF, and there is evidence of diastolic dysfunction [54]. While patients with CS are at risk for diastolic dysfunction, diastolic dysfunction is a nonspecific finding [55].
Reduced global longitudinal strain is a feature that may be present in CS with preserved ejection fraction [56], and reduction in longitudinal strain magnitude may vary inversely with LGE burden [57]. Further studies are needed to evaluate the role of strain in screening for CS.
While echocardiography has a limited sensitivity for detecting CS compared with CMR, it can be useful for evaluating the effects of pulmonary sarcoidosis and CS on hemodynamics and cardiac structure and function including left and RV size and function, valve function, and estimating right heart and pulmonary pressures. Estimation of pulmonary pressures and assessment of RV function may be particularly helpful in patients with pulmonary sarcoidosis.
Limited sensitivity of echocardiography — Echocardiography has low sensitivity for detection of CS of approximately 25 to 65 percent as compared with CMR or FDG-PET [43,51,58]. In a study of 321 patients with biopsy-proven sarcoidosis, of whom 30 percent had CS by the HRS criteria, CMR had a sensitivity of 97 percent and detected 44 patients who had symptoms or ECG abnormalities but a normal echocardiogram, as well as 15 asymptomatic patients with normal echocardiogram [58]. Despite a high positive predictive value (84 percent), echocardiography had a low sensitivity (27 percent) to detect CS and, when added to the initial screening based on cardiac history and ECG, did not provide any improvement in sensitivity. Based on the above results, in patients with extracardiac sarcoidosis who have symptoms or signs of possible cardiac involvement, echocardiography should not be used as a screening test, as a negative echocardiogram cannot be used to rule out cardiac involvement.
Cardiovascular magnetic resonance
CMR findings — CMR imaging enables the noninvasive diagnosis of subclinical or clinical CS and is the technique of choice in the evaluation of patients with suspected CS. The CMR examination should include assessment of LV and RV chamber size and function and LGE.
While CMR can detect morphologic abnormalities such as areas of wall thinning or aneurysm, the main CMR method for detecting CS is identification of regions of LGE, which are most commonly multifocal and involve the midventricular wall or subepicardium. LGE most commonly represents scar, although significant inflammation can also result in expansion of the extracellular space leading to LGE. Of note, there is no specific pattern of LGE that is pathognomonic for CS, so careful interpretation in the context of other clinical features is required [1].
The following are typical LGE patterns in patients with CS [25,59,60]:
●Multifocal areas of LGE (as opposed to a single area).
●Subepicardial and midmyocardial LGE (ie, noninfarct pattern), although some patients may have subendocardial involvement in a pattern similar to myocardial infarction (MI-type). In a series of patients with extracardiac sarcoidosis, the MI-type pattern was common among the 21 patients with LGE and no obstructive coronary disease but 86 percent of these patients had at least one region with hyperenhancement in a non-MI–type pattern [25].
●Direct LGE extension from the LV, across the interventricular segment, into the RV.
The presence of increased T2 weighted signal, a marker of increased water content, can be used to identify areas of increased inflammation, although this technique is technically challenging [20] and its role in the diagnosis of CS has not been established. Based on our experience, areas of increased T2 signal often represent inflammation, but the absence of such a signal does not reliably exclude inflammation when compared with FDG-PET imaging. Current T2 mapping techniques may overcome some of the challenges of T2 weighted imaging of the myocardium and may provide a more robust method to identify and quantify myocardial inflammation [61,62], but further validation of this technique is required before it can be adopted into routine clinical use.
Diagnostic accuracy — The main strength of CMR lies in its high negative predictive value for excluding CS when no LGE is detected. The diagnostic accuracy of LGE for detecting CS is unknown, as there is no reliable reference standard, but the sensitivity of this test likely exceeds 90 percent and has been reported to be as high as 100 percent when compared with the JMHW criteria [63]. Similarly, a study evaluating the diagnostic accuracy of CMR against the HRS criteria reported a sensitivity of 97 percent; however, this result was expected based on the study design, which only included patients with biopsy-proven sarcoidosis, and thus all patients with abnormal LGE would be categorized as having "probable CS" by HRS criteria.
However, the JMHW and HRS criteria for CS may be suboptimal reference standards against which to validate CMR and PET. Apparent false positives using JMHW or HRS criteria are more likely to reflect the limited sensitivity of these criteria (especially for patients without histologic diagnosis), rather than limited specificity of CMR and PET imaging.
Given the challenges of determining the true diagnostic accuracy of CMR, studies demonstrating the prognostic value of CMR in patients with known or suspected CS provide support for its clinical utility, as discussed separately. (See "Management and prognosis of cardiac sarcoidosis", section on 'CMR studies'.)
Limitations of CMR — Despite the high reported negative predictive value of CMR, there are rare cases when LGE can be negative in the presence of myocardial inflammation, and thus when clinical suspicion is high, a negative LGE exam cannot rule out the presence of CS.
Although some observations suggest that LGE imaging may be helpful in the assessment of the efficacy of glucocorticoid therapy [64,65], serial imaging is challenging, as patients with CS often require ICD or pacemaker implantation. These cardiac implantable electric devices may cause imaging artifacts, which may interfere with interpretation, and some devices, including most current ICDs, are not magnetic resonance imaging (MRI) compatible. The quality of LGE signal is variable, and LGE signal may be difficult to evaluate, as it often represents concomitant scar and inflammation. CMR is also less useful in assessing for extracardiac sarcoidosis than computed tomography (CT) or FDG-PET imaging.
Contraindications to CMR (eg, estimated glomerular filtration rate [eGFR] <30 mL/min/1.73 m2, implanted devices that are not MRI safe, severe claustrophobia with inability to sedate the patient) are discussed separately. Gadolinium-containing contrast agents should be avoided in patients with an eGFR <30 mL/min/1.73 m2, receiving dialysis, or with acute kidney injury. (See "Nephrogenic systemic fibrosis/nephrogenic fibrosing dermopathy in advanced kidney disease" and "Patient evaluation before gadolinium contrast administration for magnetic resonance imaging", section on 'Approach to preventing nephrogenic systemic fibrosis'.)
FDG-PET — FDG-PET can detect active myocardial inflammation, which, in the appropriate clinical context, can be used to determine the likelihood of CS. While several studies have tried to determine the diagnostic accuracy of FDG-PET [66,67], these are all limited by the use of the JMHW criteria as a reference standard, which likely has a lower accuracy than FDG-PET itself. Pooled estimates from a meta-analysis of seven studies (with 164 patients) comparing FDG-PET with the 1993 JMHW guidelines included a sensitivity of 89 percent and specificity of 78 percent [67]. FDG-PET is more sensitive than gallium-67 scintigraphy, thallium-201, or technicium-99m single-photon emission computed tomography (SPECT) [66,68,69].
A comprehensive PET imaging exam for CS involves three components:
●Rest myocardial perfusion imaging – Rest myocardial perfusion imaging can be obtained with either a SPECT or PET camera. Perfusion defects may represent either fibrosis or inflammation.
●Cardiac FDG-PET images – Cardiac FDG-PET images require a dedicated PET camera. Areas of focal FDG uptake by the myocardium represent myocardial inflammation. However, this technique requires adequate patient preparation to suppress FDG uptake from the normal myocardium [50,56]. Importantly, FDG uptake by the heart is not specific for sarcoidosis, and uptake of 18F-FDG is seen in other inflammatory myocardial diseases and hibernating myocardium. For this reason, in the appropriate clinical context, the presence of a resting perfusion defect that has increased FDG uptake requires ruling out obstructive CAD. Our recommendation is to perform either cardiac CT angiography (in lower-risk patients) or invasive angiography, as perfusion imaging will be less specific in such cases.
●Extracardiac FDG-PET images – Limited whole-body images are strongly recommended when there are no prior data regarding the presence or disease activity of extracardiac sarcoidosis. The scan range is typically performed from the orbits to the upper thigh, and at minimum should include the chest, liver, and spleen, as these are the most frequently affected organs.
The prognostic value of cardiac PET in patients with known or suspected CS is discussed separately. (See "Management and prognosis of cardiac sarcoidosis", section on 'Cardiac FDG-PET studies'.)
Comparison of CMR with FDG-PET — CMR and FDG-PET are the two imaging modalities that appear to have the highest sensitivity for detection of CS [39,40,66,70]. In addition, both CMR and FDG-PET may predict death and other adverse events. (See "Management and prognosis of cardiac sarcoidosis", section on 'Advanced cardiac imaging'.)
There are no adequate studies that are powered to compare the diagnostic accuracy of CMR and PET. Since CMR has an excellent negative predictive value to exclude prognostically significant disease (see "Management and prognosis of cardiac sarcoidosis", section on 'CMR studies'), and because it is less likely to yield nonspecific results (as can occur in 10 to 20 percent of FDG-PET cases, particularly when patient preparation is suboptimal), we suggest the use of CMR as the initial diagnostic test for patients with suspected CS who have no contraindications to CMR.
CMR and PET provide complementary information for many patients with suspected CS. CMR is more likely to provide information regarding the presence and extent of scar, while PET is more likely to provide information regarding the presence, extent, and severity of myocardial inflammation. Therefore, when any one test provides inconclusive results, we suggest combining data from both of these exams in order to determine the likelihood of CS [71-74]. (See 'Selection of advanced imaging' above.)
Endomyocardial biopsy — Detecting noncaseating granulomas is the "gold standard" for diagnosis of CS, as this finding has high specificity for sarcoidosis (picture 1). An EMB is recommended if the patient lacks histologic confirmation of noncaseating granulomas from any other source. However, the procedure has a low sensitivity, approaching 20 percent in one series of 26 patients [75]. Its use is limited by false negative results owing to sampling error that may occur due to the patchy distribution of disease. EMB is most commonly performed from the RV at the midmyocardial level, while disease involvement is more common in the basal septum and lateral LV wall, regions that are difficult to biopsy. Given the restricted area of RV midmyocardium that is safely accessible to traditional transvenous cardiac biopsy, there is only a limited role for using CMR or PET findings to guide biopsy. However, during electrophysiology (EP) study when there is suspected CS (see 'Electrophysiologic study' below), electroanatomic mapping can be used to identify areas of low voltage which may correspond to granuloma and may be targeted for biopsy, thereby increasing the diagnostic yield [76,77]. (See "Endomyocardial biopsy", section on 'Late AV block, arrhythmias, or refractory HF'.)
Additional tests — EP study or coronary angiography is indicated in the evaluation of only selected patients with suspected or known CS.
Coronary angiography — Cardiac catheterization with coronary angiography (or in younger patients with a lower likelihood of CAD, coronary CT angiography) is useful in excluding the diagnosis of atherosclerotic CAD when other testing such as CMR or PET reveals regional myocardial abnormalities that could be caused by coronary disease or sarcoidosis.
Primary sarcoidosis rarely involves the coronary arteries [78]. Although granulomatous vasculitis may cause partial or complete narrowing of the epicardial coronary arteries, thrombosis and aneurysm formation are rare. Perfusion defects in patients with known systemic sarcoidosis strongly suggest cardiac involvement if coronary angiography has excluded significant atherosclerosis. (See 'Other tests' below.)
Electrophysiologic study — While EP studies are not routinely performed for the diagnosis of CS, many patients with suspected CS undergo EP studies for risk stratification as discussed separately. (See "Management and prognosis of cardiac sarcoidosis", section on 'Role of electrophysiologic study'.)
Other tests — The following tests are not generally indicated in the diagnostic evaluation of CS:
●Nuclear myocardial perfusion imaging – Nuclear myocardial perfusion imaging is not indicated for the diagnosis of CS. However, it is important to be aware of myocardial perfusion abnormalities that may be detected in patients evaluated for CAD that may instead be caused by CS. Among patients with CS, rest nuclear myocardial perfusion imaging findings include a resting perfusion defect, with the most common locations being the basal anteroseptal, basal lateral, or basal inferior wall. Such perfusion defects, which represent scar or inflammation compressing the microvasculature, may improve following immunosuppressive therapy. However, the presence of normal myocardial perfusion at rest does not exclude the presence of CS.
●Cardiopulmonary exercise testing – Reduced oxygen uptake efficiency slope (a measure of cardiopulmonary functional reserve that is derived from the oxygen uptake and minute ventilation) has been found to have a modest sensitivity and specificity to detect CS [79]. The role of cardiopulmonary exercise testing in assessment of patients with HF is discussed separately. (See "Exercise capacity and VO2 in heart failure".)
DIFFERENTIAL DIAGNOSIS — CS should be carefully distinguished from other conditions with similar clinical presentations or cardiac imaging findings including myocarditis, other types of conduction system disease, cardiomyopathies, and ischemic heart disease. CS, Lyme carditis, and giant cell myocarditis all may present with conduction system disease. Giant cell myocarditis, often presenting with AV block, unstable ventricular arrhythmias, and acute HF, should be considered, particularly when there is a more acute or fulminant clinical presentation. Patients with myocarditis may have symptoms suggestive of a viral prodrome (eg, fever and myalgias) and are more likely to present with elevated cardiac troponin levels, but these features do not reliably distinguish between CS and myocarditis, as a viral prodrome is often absent in patients with myocarditis, and troponin elevation is common in patients with CS. Studies suggest that 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) abnormalities are common in patients with myocarditis (including giant cell myocarditis) and also have been observed in patients with cardiomyopathy (including arrhythmogenic RV cardiomyopathy) [80-83]. Patients with myocarditis may also have evidence of scar on magnetic resonance imaging (MRI) indistinguishable from that seen with CS. Endomyocardial biopsy may be required to distinguish these conditions. (See "Clinical manifestations and diagnosis of myocarditis in adults" and "Endomyocardial biopsy".)
The differential diagnosis of CS also includes other causes of AV block such as idiopathic progressive cardiac conduction disease and genetically determined arrhythmias such as SCN5A and lamin A/C disease. (See "Etiology of atrioventricular block", section on 'Pathophysiologic AV block'.)
Arrhythmogenic RV cardiomyopathy (ARVC) can also mimic CS (and vice versa) and can be challenging to differentiate [49,84]. Although early descriptions and diagnostic criteria for ARVC focused on the clinical features of RV involvement, the majority of patients with this disorder also have electrocardiographic, arrhythmic, and/or imaging evidence of LV involvement, and like CS, disease may involve the LV, RV, or both ventricles [85,86]. Useful distinguishing features between ARVC and CS include the presence of familial disease in ARVC, first-degree or higher AV block favoring the diagnosis of CS, and epi- and/or midmyocardial circumferential late gadolinium enhancement (LGE) favoring ARVC with LV involvement or one of the other inherited arrhythmogenic cardiomyopathies [87-89]. While not a criterion on the 2010 Task Force Criteria for ARVC, the presence of significant fat in the myocardium would also favor the diagnosis of ARVC. Electroanatomic voltage mapping may also be used to distinguish ARVC from isolated CS in patients presenting with right-sided ventricular arrhythmias [90]. (See "Arrhythmogenic right ventricular cardiomyopathy: Diagnostic evaluation and diagnosis".)
On imaging, CS may present with areas of increased wall thickness or areas of wall thinning and even aneurysm, and thus must be distinguished from other conditions with similar abnormalities. Fabry disease, a rare inherited disorder of fat metabolism, can present with concentric or asymmetric LV hypertrophy, and on MRI often has midwall LGE of the basal inferolateral wall (see "Fabry disease: Cardiovascular disease", section on 'Cardiac tests'). While such LGE findings can also be seen in CS, CS is more likely to have multifocal LGE and focal areas of LV hypertrophy. LV noncompaction may present with ventricular arrhythmia and increased wall thickness much like CS, but in noncompaction increased trabeculations of the ventricular myocardium are detected on echocardiography or cardiac magnetic resonance (CMR) (see "Isolated left ventricular noncompaction in adults: Clinical manifestations and diagnosis", section on 'Diagnosis'). Cardiac iron overload from hereditary hemochromatosis can present with conduction disease, arrhythmia, and HF much like CS, but hemochromatosis may be accompanied by diabetes and bronze skin and can be diagnosed by reduced T2* signal on CMR (see "Approach to the patient with suspected iron overload"). In rare cases, CS may also resemble end-stage hypertrophic cardiomyopathy where there is significant replacement fibrosis of the LV. (See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation", section on 'Diagnostic evaluation'.)
Right HF due to CS involving the RV should be distinguished from other causes of right HF such as right HF secondary to left HF (which may be caused by CS) and right HF caused by pulmonary sarcoidosis (cor pulmonale). (See 'Cardiomyopathy and heart failure' above.)
Cor pulmonale secondary to pulmonary sarcoidosis should be distinguished from CS involving the RV. Pulmonary hypertension is a complication in some patients (estimated at 3 to 20 percent) with pulmonary sarcoidosis [91] and often occurs in the absence of CS. Some patients with pulmonary hypertension may develop right HF. Patients who have pulmonary sarcoidosis with cor pulmonale can have areas of focal LGE on MRI at the RV insertion points. Such findings are well described in patients with pulmonary hypertension and should be distinguished from CS where the LGE involvement is more extensive, and often extends beyond the insertion points to involve the RV and LV.
While most patients with CS have subepicardial or midwall LGE involvement on MRI, some can have subendocardial LGE, which is a pattern most commonly seen in patients who have had prior myocardial infarctions. Similarly, CS may be detected on FDG-PET by a rest perfusion defect associated with increased FDG uptake. However, such a pattern can also be seen in patients with hibernating myocardium, and thus the presence of obstructive coronary artery disease should be ruled out in such scenarios. (See "Evaluation of hibernating myocardium" and "Clinical syndromes of stunned or hibernating myocardium" and "Treatment of ischemic cardiomyopathy".)
Other diseases that can mimic CS include Chagas disease and tuberculosis. Both can cause cardiac aneurysms and ventricular arrhythmias. (See "Chronic Chagas cardiomyopathy: Clinical manifestations and diagnosis" and "Sustained monomorphic ventricular tachycardia: Clinical manifestations, diagnosis, and evaluation", section on 'Epidemiology and risk factors'.)
Genetic cardiomyopathies, including those caused by mutations in desmosomal and lamin A/C protein genes, share some clinical characteristics with CS but have differing histologic characteristics. Genetic testing may be particularly useful in unresolved cases of suspected sarcoid without histologic confirmation, particularly when clinical manifestations and imaging abnormalities are isolated to the heart. (See "Genetics of dilated cardiomyopathy".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Sarcoidosis" and "Society guideline links: Heart failure in adults" and "Society guideline links: Myocarditis" and "Society guideline links: Cardiomyopathy".)
SUMMARY AND RECOMMENDATIONS
●Cardiac sarcoidosis (CS) is common, occurring in 20 percent or more of patients with systemic sarcoidosis, but the true prevalence remains unknown and is likely underestimated since many individuals with CS may have nonspecific symptoms or subclinical disease. (See 'Prevalence' above.)
●Up to 25 percent of cases of CS are isolated (occur without extracardiac involvement), and thus absence of extracardiac sarcoidosis does not exclude CS. (See 'Prevalence' above.)
●The clinical presentation of CS ranges from an incidentally discovered condition to syncope, heart failure, and sudden death. (See 'Clinical manifestations' above.)
●Patients with extracardiac sarcoidosis who lack one or more of the symptoms and signs of CS that serve as indications for advanced imaging are unlikely to benefit from further immediate evaluation. Serial (eg, annual) cardiac examinations and electrocardiograms are recommended to detect development of symptoms or signs of CS. (See 'Patients without criteria for advanced cardiac imaging' above.)
●The diagnosis of CS requires appropriate clinical suspicion and often requires integrating clinical and pathologic data together with the results of advanced cardiac imaging. Diagnostic certainty of CS ranges from "definite" to "probable" (≥50 percent). (See 'Diagnosis' above.)
●In patients who have known extracardiac sarcoidosis, characteristic cardiac magnetic resonance imaging (CMR) or 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) findings can be used to confirm the diagnosis of CS. Endomyocardial biopsy is often not required. (See 'How to diagnose cardiac sarcoidosis' above.)
●In the absence of biopsy-proven extracardiac sarcoidosis, or when data are inconclusive, integrating data from CMR imaging and FDG-PET may be useful for establishing the likelihood of CS. (See 'Uncertain diagnosis' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff thanks Talmadge King Jr., MD, who contributed as section editor to an earlier version of this topic review.
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