Australian Doctor Australian Doctor 7th July 2017

How to Treat – Myocarditis EMB IS INFREQUENTLY PERFORMED BECAUSE OF ITS LOW SENSITIVITY, LACK OF AVAILABILITY AND RISK AS AN INVASIVE PROCEDURE. from page 22 decreased left ventricular func- tion. 28 Cardiovascular magnetic resonance CMR, where available, is con- sidered to be a fundamental non-invasive diagnostic tool for investigating patients with acute non-ischaemic myocardial injury, including those with suspected myocarditis. It provides the most comprehensive and accurate information regarding functional abnormality, morphological changes and tissue characterisa- tion (myocardial oedema, hyper- aemia and necrosis). 23,29 Myocardial oedema is detected as an area of high signal intensity in T2-weighted images. Hyperae- mia representing vasodilatation is an integral feature of tissue inflam- mation. The increased blood volume in this area leads to an increased uptake of gadolinium contrast. Because the agents dis- perse quickly into the interstitial space after administration, myo- cardial early gadolinium enhance- ment ratio is intended to detect an increased volume of the contrast distribution into the intravascular and interstitial space during the early washout period. 30 Fibrosis in myocarditis is dis- tinguished by patchy, bright late- gadolinium-enhanced area with focal, intramural or subepicar- dial localisation, usually affecting the inferolateral segments and, less frequently, the anteroseptal region. 30,31 Contrast-enhanced CMR in patients with chronic symptoms in the absence of coro- nary artery disease may non-inva- sively identify areas of myocardial damage, suggesting the presence of a myocardial inflammatory process. The international consensus on CMR criteria for diagnosing clini- cally suspected myocarditis state that if two or more of the follow- ing three components are positive, active myocardial inflammation can be predicted: I. Increase in regional or global myocardial signal intensity in T2-weighted images of ≥2.0. Increase in global myocardial II. early gadolinium enhancement ratio between myocardium and skeletal muscle in gadolinium- enhanced T1-weighted images of ≥4.0. III. The presence of at least one Eosinophilic myocarditis on H&E stain. Source: Journal of Cardiovascular Magnetic Resonance 2008; 10:21 http://bit. ly/2pWe1mJ X-ray dilated cardiomyopathy Source: Abdullah Sarhan http://bit.ly/2qkbsvX focal non-ischaemic lesion at late gadolinium enhance- ment. 30 If the initial CMR is normal, the recommendation is to repeat the study between the first and sec- ond week after the initial scan if the clinical suspicion is still high and the onset of symptoms is very recent. If left ventricular dysfunc- tion or pericardial effusion is found, this is additional informa- tion that supports the presence of myocarditis. 30 Endomyocardial biopsy The Heart Failure Society of Suspected myocarditis • Viral prodrome • Chest pain • Heart failure • Arrhythmia • Cardiogenic shock Initial investigation America 2010 Comprehensive Heart Failure Practice Guideline recommends considering EMB for patients with acute deterioration of heart function of unknown ori- gin that is not responding to guide- line-directed medical therapy. 32 EMB is helpful in establishing the diagnosis, treatment options and prognosis in fulminant myo- carditis, giant-cell myocarditis, chronic active myocarditis, eosin- ophilic myocarditis (Löffler syn- drome) and myocardial sarcoid. Other indications for EMB include the evaluation of patients who are clinically unresponsive to • ECG • Biomarkers • Echocardiogram • CMR Coronary angiogram Indications: • ACS-like presentation • LV dysfuction • Prior to EMB Figure 4. The practical approach to myocarditis. Source: Caforio et al, Hazebroek M et al. 3,23 24 | Australian Doctor | 7 July 2017 supportive therapy, as well as those with conduction disturbances and malignant arrhythmias, in whom giant-cell myocarditis must be ruled out. 15 Despite claims that it is the ultimate diagnostic tool for myo- carditis, EMB is infrequently performed because of its low sen- sitivity, lack of availability and risk as an invasive procedure. Sampling error and intra-observer variability in identification of inflammatory infiltrates impose significant limitation on the diag- nostic accuracy. Because of patchy distribution of the inflammatory cells, biopsy sometimes has a risk of false-nega- tive results. Therefore, the absence of histological evidence should not preclude the diagnosis of myocar- ditis in the appropriate clinical set- tings. CMR and echocardiography may help guide EMB sampling and increase the diagnostic yield for detecting myocarditis. Patients undergoing EMB are at risk of complications. The overall complication rate is reported as less than 6% in most case series. Life-threatening complications, such as perforation and tampon- ade, occur far less frequently, in 0.1 to 0.5% of cases. 33 EMB has greater sensitivity when the tissue samples use a combined histology, immunohis- tochemistry and viral genomes analysis. The histology of inflammation in the myocardium is defined by www.australiandoctor.com.au EMB the Dallas criteria. Based on his- topathological criteria, several distinct types of myocarditis have been identified: lymphocytic, eosinophilic, polymorphous, giant-cell and granulomatous myocarditis. Biopsied cardiac tissue is con- sidered to be inflamed by immu- nohistochemical detection of mononuclear infiltrates (T lym- phocytes and macrophages) and enhanced expression of HLA class II antigen. “Immunohistochemical staining has enabled more precise characterisation of infiltrating lymphocytes subtypes” and can accurately define and quantify upregulation of major histocom- patibility antigens. 34 Myocyte-specific major his- tocompatibility antigen expres- sion is reported to be increased in myocarditis and represents a more chronic form of myocardial injury. This can be used to select patients who will benefit f

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