Diagnosis of myocarditis belongs to one of the most challenging in cardiology because of many reasons. One of them is, for example, an enormous variability of symptoms and manifestations of the disease including asymptomatic individuals, heart failure, cardiogenic shock, sudden death and patients with myocarditis mimicking ischemic heart disease. There is no single examination which could confirm the diagnosis with 100% certainty. Diagnosis is thus very frequently based on a process of elimination.
There are all kinds of examinations used for the diagnosis of myocarditis and ICMP – ECG, ECHO, laboratory examination of the myocardial damage, CMRI and EMB.
Patients with myocarditis, alternatively with ICMP, have heterogenous inconveniences and symptoms. In up to 60 % of cases, the disease is most commonly preceded by a viral infection of the gastrointestinal or respiratory system.
Signs of the disease are chest pain, nausea, dyspnoea, fever, flu-like symptoms, arthralgia and myalgia, rash (in hypersensitive reaction), peripheral oedema, palpitation, and syncope. In children, the absence of appetite, abdominal pain, vomiting and in severe cases cyanosis may occur.
Physical examination findings may be even normal or poor. Besides the above-mentioned symptoms, even tachypnoea, tachycardia, worse tangible peripheral pulsation, thromboembolic symptoms etc.
ECG changes in patients with myocarditis are varied. In up to ¼ of patients, ECG findings are normal.
There are often described non-specific repolarization changes, elevation or depression of ST segment (changes in repolarization may mimick heart attack), T wave inversion, prolonged PQ and QT intervals or widened QRS complex, pathological Q wave, lower voltage of QRS complex and ventricular or supraventricular premature beats, bundle branch block, AV block of the 1st to 3rd degree and different types of supraventricular and ventricular arrhythmias.
The echocardiographic examination has, similar to ECG, its role primarily in stratification and observation of patients´ state of health and it has a role even in the exclusion of other symptoms and cardiac dysfunction causes.
There are a number of described findings and the diagnosis of myocarditis is not excluded even by normal ECHO finding.
There may be observed for example following findings – regional or global impairment of the left and/or right ventricular kinetics, heart chambers dilatation, pericardial effusion and decreased diastolic and global systolic left and/or right function.
Chest X-Ray may visualize cardiomegaly and bigger pericardial effusion, pleural effusion or congestion in the pulmonary circulation. The finding may be even normal.
Cardiac magnetic resonance is in the present the leading non-invasive imaging method for patients with myocarditis. CMRI advantages are primarily in its ability of the structural and functional heart characteristics evaluation with higher accuracy than ECHO, and it is primarily used for the evaluation of changes of the myocardial tissue characteristics, when it is possible to detect the myocardial oedema, myocardial hyperaemia as a result of the inflammatory process, and especially necrosis or in later phases fibrosis of the myocardium. Diagnosis of myocarditis is further supported by the presence of the pericardial effusion. Gadolinium contrast agent is administered to the patients for the evaluation of the myocardial necrosis/fibrosis.
An important part of this examination is the evaluation of LGE (late gadolinium enhancement) which proves myocardial necrosis or in later phases fibrosis of the myocardium.
To increase the utilization of the examination, Lake Louise Criteria have been created. However, negative CMRI result does not exclude the diagnosis of myocarditis.
Laboratory examination consists of basic examinations and the detection of biomarkers of the myocardial damage, heat failure and inflammation. The testing of anti-myocardial autoantibodies is recommended by the European Society of Cardiology, on the contrary, routine serological testing is not recommended, because of its low contribution to the diagnosis. It is pointed out in a number of references that negativity of inflammation markers and biomarkers of the myocardial necrosis does not exclude the diagnosis of myocarditis.
There are several biomarkers of the myocardial necrosis used in clinical practice – levels of troponin T or I, creatine kinase (CK), primarily its myocardial form (CK-MB), alternatively of myoglobin [26]. As a biomarker of heart failure, detection of natriuretic B peptides (BNP) or their prohormone (pro-BNP) is used.
EMB is an invasive diagnostic method which is described in many references as a gold standard in the diagnosis of myocarditis and ICMP and which definitively confirms the diagnosis and has also an important role in the determination of the disease aetiology. Its indication still follows the recommendations of the American and European Society of Cardiology from the year 2007. It is recommended primarily in two clinical scenarios: “1. New-onset heart failure of less than 2 weeks’ duration associated with a normal-sized or dilated left ventricle and hemodynamic compromise. 2. New-onset heart failure of 2 weeks’ to 3 months’ duration associated with a dilated left ventricle and new ventricular arrhythmias, second- or third-degree heart block, or failure to respond to usual care within 1 to 2 weeks.”