Introduction
The heart is one of the most important organs of the human body. It is a muscular organ that pumps oxygenated blood throughout the body. Also, carbon dioxide-rich deoxygenated blood is in the lung. In short, the heart is responsible for blood circulation in the body. Blood circulation maintains oxygen concentration, ion balance, and balance of the nutrients in the body. So, overall tissue performance is maintained by the heart. Heart muscle plays a pivotal role in maintaining cardiac performance. The muscles of the heart are known as the myocardium. Any condition that affects the normal physical condition of the myocardium.
What Is Myocarditis?
The muscle of the heart is known as the myocardium. It is the middle and thickest layer of the heart. These muscles are composed of cells known as cardiomyocytes. These cells are exclusively found in the heart. The presence of a single nucleus and striation are the distinctive features of these cells. The presence of intercalated discs (a disc that is helpful in cellular adhesion) also improves the contractile ability of these muscles.
The infection and inflammation of the cardiac muscles are known as myocarditis. This reduces the ability of the heart to pump blood properly. The pathogenesis of myocarditis is as follows:
-
The injury of the myocardium is the first step of myocarditis. Cardiac infection or other factors like autoimmune conditions may lead to damage to the cardiac muscles. This damage is caused by the destruction of muscle proteins. This causes activation of the Toll-like receptors (TLRs) and the inflammasome and initiates the secretion of inflammatory mediators. The release of proinflammatory cytokines and molecules like TLR2 and TLR4 causes the activation of macrophages. All these factors are responsible for the destruction of cardiac proteins like myosin.
-
In the second phase, acute myocardial infection is seen. In this condition, infiltration of macrophages, neutrophils, and T and B lymphocytes can be seen. Various chemical substances released by these cells are responsible for cardiac muscle remodeling and leading to fibrosis.
-
After a certain time, these cellular changes lead to low-grade inflammation. Chemicals released during this process lead to the death of the muscle cells, muscular hypertrophy, contractile dysfunction, and extracellular modeling.
All these factors and responsible for changes in muscle physiology and its form and functioning.
The main cause of myocarditis is various viral infections.
Other than this, other factors are also associated with myocarditis. These are:
-
Bacterial infection.
-
Fungal infection.
-
Rheumatic fever.
-
Autoimmune disorders.
What Is Bacterial Myocarditis?
Bacterial infections are one of the most common causes of myocarditis in young individuals. Group A streptococcus, such as streptococcus pyogenes, a beta-hemolytic bacterium, is the most common bacteria related to bacterial myocarditis. Other than this, streptococcus mutans, a common bacteria responsible for teeth caries and dental plaque formation, is associated with bacterial myocarditis.
Bacterial infectious conditions like scarlet fever and pharyngitis are related to bacterial myocarditis. Apart from this, corynebacterium diphtheria, the causative organism responsible for diphtheria, releases several toxins that are responsible for myocarditis. Around 19 to 68 percent of patients suffering from diphtheria develop myocarditis.
Typhoid fever may also be responsible for myocarditis. Salmonella typhi, the causative organism for typhoid fever, is responsible for inflammation of the heart's intramural vessels, microcirculatory disturbances, and edema. These factors are responsible for developing myocarditis in such cases.
Meningitis caused by Meningococcus species can also cause bacterial myocarditis.
What Is Fungal Myocarditis?
Fungal myocarditis is a rare entity. It is mainly caused by fungal infection in immunocompromised persons. Persons suffering from HIV (human immunodeficiency virus) infection, patients receiving radio or chemotherapy, excessive use of broad-spectrum antibiotics, and prolonged corticosteroid therapy are associated with fungal infections. Fungal spices that are associated with myocarditis are:
-
Candida albicans, Candida parapsilosis, and Candida tropicalis.
-
Cryptococcus neoformans.
-
Aspergillus species.
-
Coccidioides immitis.
-
Histoplasma capsulatum.
-
Blastomyces dermatitidis
What Is the Role of Rheumatic Fever?
Rheumatic fever is an autoimmune inflammatory condition that is developed when a sore throat, skin infection, or scarlet fever is not treated properly. Streptococcus pyogenes is responsible for such infections. If not treated properly, these infections lead to the production of autoantibodies. These autoantibodies are associated with rheumatic fever myocarditis. The presence of nodules (Aschoff bodies) in the lung tissues is the main clinical feature of this condition.
What Is the Effect of Autoimmune Disorders?
Autoimmune disorder-induced myocarditis is also known as immune checkpoint
inhibitor (ICI)-induced myocarditis. Conditions like lupus erythematosus are associated with such type of myocarditis. The presence of immune cell infiltrates and abnormal expression of HLA (human leucocyte adhesion molecule) molecules and heart-specific autoantibodies in such cases are responsible for developing myocarditis.
What are the Symptoms of Nonviral Myocarditis?
The symptoms of myocarditis are:
-
Shortness of breath and breathing difficulty.
-
Tiredness and breathlessness after mild to moderate exercise.
-
Pain in the chest and heaviness in the chest.
-
Frequent history of fainting.
-
Swelling in the leg.
On diagnostic examination, following features can be diagnosed:
-
A chest x-ray will reveal the increased size of the heart and the presence of fluid in the lungs.
-
Magnetic resonance imaging of the chest shows an enlargement of the cardiac muscles, and increased ventricular dimensions are also observed. The presence of fluid around the lungs (pleural effusion) can also be seen.
-
Cardiac magnetic imaging is a gold standard method for the detection of myocarditis. Inflammation of cardiac muscles and myocardial edema (presence of fluid) can be detected using this method.
-
Echocardiogram is essential for the detection of myocardial damage, valvular heart diseases, or intracardiac thrombus.
-
An endomyocardial biopsy is done to obtain samples from cardiac muscles. The exact cause of myocarditis or its type can be diagnosed using this method.
What Is the Treatment of Myocarditis?
The treatment of myocarditis depends upon various factors. The causative factors like bacterial and fungal infection or autoimmune conditions must be treated. The treatment of myocarditis is depended upon the extent of the heart damage. Medicines like beta-blocker, renin-angiotensin-aldosterone (RAAS) inhibitors, mineralocorticoid receptor antagonists (MRA), sodium-glucose co-transporter-2 inhibitors (SGLT-2 inhibitors) can be used for the treatment of heart failure. Pacemakers can be placed in patients with heart blocks. Lifestyle management like smoking cessation, stoppage of alcohol, and limited exercise can also be advised.
Conclusion:
Myocarditis is a life-threatening condition. Bacterial infections or fungal infections in immunocompromised persons are responsible for this condition. Autoimmune disorders are also responsible for this. If not diagnosed properly, these may lead to cardiac failure, a rhythmic problem of the heath, and may even cause death.
