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Circulation. 2021;144:e368–e454. DOI: 10.1161/CIR.0000000000001029 November 30, 2021 e403 CLINICAL STATEMENTS AND GUIDELINES

Synopsis Pericarditis and myocarditis share overlapping common causes and likely form a continuum.8 In patients with pericarditis, a minimally elevated troponin does not appear to confer a worse prognosis.14 Most cases of pericarditis in developed nations are viral, although tuberculosis is sometimes a consideration. Pericarditis classically presents with chest pain that is sharp, pleuritic, and which may be improved by sitting up or leaning forward, although in many instances such findings are not present. A pericardial friction rub may be audible. Widespread ST-elevation with PR depression is the electrocardiographic hallmark, although changes are nonspecific and may be transient. Clinical manifestations of myocarditis are varied and include chest pain that is often sharp and reflective of epicardial inflammation involving the pericardium. Myocardial dysfunction often causes fatigue and exercise intolerance, and predominance of heart failure distinguishes myocarditis from pericarditis. Troponin is usually elevated.15

Recommendation-Specific Supportive Text

1.	 CMR with late gadolinium enhancement imaging can show characteristic changes of acute myopericarditis, especially if performed early, within 2 weeks of the index presentation. CMR can also frequently distinguish between acute myopericarditis, other cardiomyopathies, and occult MI and other causes of MI and nonobstructive coronary arteries.1,2 2.	 In patients with suspected acute myopericarditis, or if there is diagnostic uncertainty, CMR is useful to determine myocardial edema, thickening, and late enhancement. CMR may also show evidence of pericardial effusions.2,16 CMR has a sensitivity of 94% to 100% in detecting inflammation of the pericardium.7-10 CMR features that are suggestive of acute pericarditis include enhancement or thickened pericardium, although such findings can also be seen in the presence of pericardial fibrosis. In addition, increased signal on T2-weighted images correlates with edema, which may be seen in acute myopericarditis. The presence of pericardial adhesions between the visceral and parietal pericardium may be useful in patients with suspected acute pericarditis or pericardial constriction.7-10 3.	 In patients with suspected myopericarditis, echocardiography may show segmental left ventricular wall hypokinesis, which suggests myocardial involvement in patients with myocarditis and is, therefore, a useful tool in these patients. Patients with acute pericarditis may also have echocardiographic findings such as increased pericardial brightness or pericardial effusion with or without tamponade physiology. Some patients with acute pericarditis may also have normal echocardiographic findings.9,17

4.	 In patients with suspected acute pericarditis, cardiac CT with or without contrast may show features that are suggestive of acute pericarditis, such as pericardial thickening or enhancement (after contrast administration). Additionally, CT attenuation values of pericardial effusion can help distinguish between exudative and transudative pericardial fluid. There are limited data on the accuracy of cardiac CT in diagnosing acute pericarditis; a small study showed that pericardial thickening or enhancement was the most accurate single parameter for pericarditis, with sensitivity of 54% to 59% and specificity of 91% to 96%. Therefore, cardiac CT is a reasonable second-line study in these patients.7,8,13

4.2.4 Acute Chest Pain With Valvular Heart Disease (VHD)

Recommendations for Acute Chest Pain With VHD

COR LOE Recommendations

1 C-EO 1.	 In patients presenting with acute chest pain with suspected or known history of VHD, TTE is useful in determining the presence, severity, and cause of VHD.

1 C-EO 2.	 In patients presenting with acute chest pain with suspected or known VHD in whom TTE diagnostic quality is inadequate, TEE (with 3D imaging if available) is useful in determining the severity and cause of VHD.

2a C-EO 3.	 In patients presenting with acute chest pain with known or suspected VHD, CMR imaging is reasonable as an alternative to TTE and/or TEE is nondiagnostic.

Synopsis Chest pain may occur in the presence of VHD, particularly stenotic VHD such as aortic valve stenosis and mitral valve stenosis with secondary pulmonary hypertension. Chest pain may also occur after papillary muscle rupture in the setting of MI or in acute degenerative mitral valve disease after spontaneous chordal rupture. Chest pain may also occur in the setting of acute severe aortic insufficiency, which may be related to acute aortic pathology such as an aortic dissection manifesting as severe acute chest pain that may radiate to the back. The cause of chest pain in patients with aortic valve stenosis may be secondary to coexisting obstructive epicardial CAD1 or, more commonly, chest pain may occur as a result of coronary microvascular dysfunction2 in the presence of very elevated left ventricular pressure caused by a high left ventricular afterload, along with the associated left ventricular hypertrophy. The cause of chest pain in patients with severe mitral

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