The Current and Emerging Role of Cardiovascular Magnetic Resonance in the Diagnosis of Nonischemic Cardiomyopathies

Contrast-enhanced cine MR sequences in the assessment of myocardial hyperemia in acute myocarditis: can they help? A feasibility study

The study was designed to assess the accuracy of contrast-enhanced balanced steady-state free precession (cine-SSFP) CMR imaging sequences to exhibit myocardial hyperemia in acute myocarditis, which has for a long time been investigated in some centers using early gadolinium enhancement (EGE) sequence. Contrast-enhanced cine-SSFP (CESSFP) sequences were compared to precontrast cine-SSFP sequences to calculate the early cine-contrast enhancement in 36 consecutive patients with acute myocarditis and 36 controls matched for age and gender. Four-chamber views images were obtained in each subject before and after gadolinium injection. Absolute and relative left ventricular myocardial enhancement of the overall myocardium, then separately of the lateral wall and interventricular septum was analyzed in telediastole. Myocarditis patients displayed higher cine-SSFP absolute enhancement than controls (overall left ventricular myocardium 2.38 ± 0.33 vs 1.84 ± 0.31; lateral wall 2.45 ± 0.35 vs 1.83 ± 0.32; and septum 2.26 ± 0.29 vs 1.82 ± 0.29, p < 0.0001 for all). Less significant differences were observed for the relative enhancement (p < 0.05 for all). Using ROC curves, the optimal threshold value of absolute enhancement to diagnose acute myocarditis was 2.05 (sensitivity: 86%; specificity: 81%). Given the simplicity of use, contrast-enhanced cine-SSFP sequences should be used as an additional diagnostic tool to detect hyperemia in acute myocarditis patients.

A Review of the Role of Imaging Modalities in the Evaluation of Viral Myocarditis with a Special Focus on COVID-19-Related Myocarditis

Viral myocarditis is inflammation of the myocardium secondary to viral infection. The clinical presentation of viral myocarditis is very heterogeneous and can range from nonspecific symptoms of malaise and fatigue in subclinical disease to a more florid presentation, such as acute cardiogenic shock and sudden cardiac death in severe cases. The accurate and prompt diagnosis of viral myocarditis is very challenging. Endomyocardial biopsy is considered to be the gold standard test to confirm viral myocarditis; however, it is an invasive procedure, and the sensitivity is low when myocardial involvement is focal. Cardiac imaging hence plays an essential role in the noninvasive evaluation of viral myocarditis. The current coronavirus disease 2019 (COVID-19) pandemic has generated considerable interest in the use of imaging in the early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related myocarditis. This article reviews the role of various cardiac imaging modalities used in the diagnosis and assessment of viral myocarditis, including COVID-19-related myocarditis.

The unique role of cardiovascular magnetic resonance imaging in acute myocarditis

This article addresses the specific diagnostic information provided by cardiovascular magnetic resonance (CMR) in patients with suspected acute myocarditis. It gives an overview of the current evidence of the ability of CMR to detect myocardial inflammation and discusses the added value as well as its limitations in clinical settings. Because of the large variety of symptoms and the limited specificity of other non-invasive procedures, the identification of myocardial inflammation is of paramount importance. Because of its accuracy in imaging ventricular volumes and function and its unique ability to visualize myocardial edema, scar, and other tissue abnormalities, CMR has emerged as the prime non-invasive diagnostic tool in patients with acute myocarditis. The presence of myocardial inflammation is not specific to viral myocarditis or other forms of acute myocardial injury, and the regional distribution within the myocardium helps differentiate acute myocarditis from other diseases. The currently recommended diagnostic criteria (Lake Louise Criteria) include markers for hyperemia/capillary leak, edema, and inflammatory scarring. Their diagnostic accuracy of close to 80% is satisfactory to rule in myocarditis, yet the negative predictive value is less than 70%. Novel CMR techniques, especially T1 and T2 mapping, have been shown to further improve the diagnostic utility.

Role of Cardiac MR Imaging in Cardiomyopathies

Cardiac MR imaging has made major inroads in the new millennium in the diagnosis and assessment of prognosis for patients with cardiomyopathies. Imaging of left and right ventricular structure and function and tissue characterization with late gadolinium enhancement (LGE) as well as T1 and T2 mapping enable accurate diagnosis of the underlying etiology. In the setting of coronary artery disease, either transmurality of LGE or contractile reserve in response to dobutamine can assess the likelihood of recovery of function after revascularization. The presence of scar reduces the likelihood of a response to medical therapy and to cardiac resynchronization therapy in heart failure. The presence and extent of LGE relate to overall cardiovascular outcome in cardiomyopathies. A major role for cardiac MR imaging in cardiomyopathies is to identify myocardial scar for diagnostic and prognostic purposes.

Magnetic Resonance Imaging of Hypertrophic Cardiomyopathy: Beyond Left Ventricular Wall Thickness

During the past decade, cardiac magnetic resonance has gained increasing popularity in the diagnosis of hypertrophic cardiomyopathy because of its greater accuracy and better characterization of cardiac morphology compared with other imaging modalities. In this pictorial essay, a global clinical portrait of hypertrophic cardiomyopathy will be drawn. The various radiologic findings associated with each variant of hypertrophic cardiomyopathy, and the clinical edge offered by cardiac magnetic resonance will be discussed.

ACR appropriateness criteria® nonischemic myocardial disease with clinical manifestations (ischemic cardiomyopathy already excluded)

Nonischemic myocardial disease or cardiomyopathy can present as arrhythmia, palpitations, heart failure, dyspnea, lower extremity edema, ascites, syncope, and/or chest discomfort and can be classified as either systolic, diastolic, or a combination of both. Echocardiography is the mainstay of evaluating left ventricular function. However, cardiac magnetic resonance imaging (MRI) is now considered the reference standard imaging technique to assess myocardial anatomy, function, and viability. Advanced MRI techniques with delayed myocardial enhancement, especially, can provide information beyond echocardiography for tissue characterization in CM and can assist in determining specific etiology or in narrowing the differential. Often imaging enhancement patterns, signal characteristics, and morphology on MRI can lead to specific diagnoses such as amyloidosis, hypertrophic CM, or iron deposition. Cardiac computed tomography is usually used in excluding coronary artery disease but can also be used in some patients unable to undergo cardiac MRI to assess arrhythmogenic right ventricular dysplasia. Both 18-F-fluoro-2-deoxyglucose positron emission tomography and delayed contrast-enhanced MRI can be used to assess for cardiac sarcoidosis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.