Myocarditis is a public health disease resulting in sudden heart failure in young adults, specifically over the past decade. It is an inflammatory disease of the myocardium surrounding the heart leading to tissue level damage. Autoimmune myocarditis generally refers to the body’s immune system going against the body itself, thus, inducing inflammation and damage to the heart muscles or myocardium.
Contributing factors such as having a systemic autoimmune disease, exposures to toxins, or hypersensitivity to medications may induce myocarditis via an autoimmune reaction. Even when this is caused by a virus, which is one of the foremost reasons for death due to myocarditis, an autoimmune reaction like antigen mimicry may be induced which can be regarded as autoimmune-driven myocarditis. A very specific cause of autoimmune myocarditis is the immune checkpoint inhibitor (ICI)-induced myocarditis, which is an outcome of drug therapy in cancers.
According to the World Health Organisation (WHO) classification of cardiomyopathies, there are primarily three distinct cardiomyopathies (1) idiopathic, (2) infectious or autoimmune, and (3) dilated cardiomyopathy or DCM based on the stages of inflammation. The worldwide incidence of myocarditis as reported five years back by the Global Burden of Disease project was 3,071,000 cases.
The symptoms follow diverse clinical presentations, ranging from chest pain to acute cardiogenic shock. The patients can also develop temporary or permanent impairment of cardiac functions including acute cardiomyopathy with hemodynamic compromise or severe arrhythmias. However, myocarditis, for the most part, is underdiagnosed due to a large number of asymptomatic cases. Nevertheless, it remains one of the most significant causes of DCM with up to 30% of cases progressing to DCM.
The signs and distinct symptoms of symptomatic autoimmune myocarditis may consist of:
Abnormal heartbeat or arrhythmias
Shortness of breath, fatigue
Swelling in the legs
Signs of infection such as fever
Swelling of extremities
Diagnosis of autoimmune myocarditis is primarily based on clinical observation findings. For viral myocarditis, the detection of pathogens and associated symptoms are to be sought. Simultaneously, pre-existing cardiovascular disease or other causes that may explain the clinical condition must be confirmed or excluded before confirming myocarditis.
Some diagnostic techniques and tools are:
Cardiac magnetic resonance imaging or CMR imaging
Endomyocardial biopsy or EMB remains the gold standard
Cardiac marker testing such as cardiac troponins, creatine kinase, and myoglobin levels
Patients with hemodynamically stable conditions, but having heart failure should be treated with diuretics to expel the undesired amount of water and salts in the form of urine, from the body leading to relaxation of the pressure of the blood vessels. Such patients can also be treated with angiotensin-converting enzyme inhibitor or angiotensin receptor blockers, which also works by relaxation of blood vessels and decrease in blood volume to reduce blood pressure in patients. Moreover, beta-adrenergic blockers may also be utilized which block the effect of epinephrine hormones leading to reduced heart rate along with lowering blood pressure and thus preventing the possibility of a heart attack.
In persistent heart failure despite the optimal management, additional treatment with aldosterone antagonists may be considered. Specifically, in autoimmune myocarditis with common systemic disorders, high-dose intravenous immunoglobulin (IVIG) is therapeutic, which is a promising option. Some novel treatment strategies include (1) specific epitope-derived peptides as autoantibody-scavengers, (2) direct targeting/suppression of antibody-producing B cells and/or plasma cells, and 3) immunoadsorption (IA) of disease-causing antibodies. The management should include long-term follow-up of autoimmune myocarditis patients with clinical observation as well as non-invasive cardiac examination with imaging and inclusion of steroids as immunosuppressants. Cardiac transplantation should be the last resort for patients with severe complications. The early monitoring of autoimmune myocarditis is required to reduce the growing incidences of heart attacks. The detection through imaging techniques and management with subsequent follow-ups are highly needed.