Myocarditis is inflammation of the cardiac muscle. Myocarditis can progress to inflammatory cardiomyopathy when there is associated ventricular remodeling and cardiac dysfunction due to chronic inflammation. Symptoms can include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The duration of problems can vary from hours to months. Complications may include heart failure, due to dilated cardiomyopathy or cardiac arrest. Myocarditis is most often due to a viral infection. Other causes include bacterial infections, certain medications, toxins and autoimmune disorders. A diagnosis may be supported by an electrocardiogram (ECG), increased troponin, heart MRI, and occasionally a heart biopsy. An ultrasound of the heart is important to rule out other potential causes, such as heart valve problems. Treatment depends on both the severity and the cause. Medications such as ACE inhibitors, beta blockers, and diuretics are often used. A period of no exercise is typically recommended during recovery. Corticosteroids or intravenous immunoglobulin (IVIG) may be useful in certain cases. In severe cases, an implantable cardiac defibrillator or heart transplant may be recommended. In 2013, about 1.5 million cases of acute myocarditis occurred. While people of all ages are affected, the young are most often affected. It is slightly more common in males than females. Most cases are mild. In 2015, cardiomyopathy, including myocarditis, resulted in 354,000 deaths, up from 294,000 in 1990. The initial descriptions of the condition are from the mid-1800s.
Signs and symptoms The signs and symptoms associated with myocarditis are varied, and relate either to the actual inflammation of the myocardium or to the weakness and dysfunction of the heart muscle that is secondary to the inflammation. While myocarditis may develop over periods ranging from hours to months, patients typically present with signs and symptoms that resemble heart failure, including the following:
Since myocarditis is often due to a viral illness, many patients experience symptoms consistent with a recent viral infection including a fever, rash, loss of appetite, abdominal pain, vomiting, diarrhea, joint pains, and easily becoming tired. Additionally, myocarditis is often associated with pericarditis, and many people with myocarditis present with signs and symptoms that suggest myocarditis and pericarditis at the same time. Children primarily present with the aforementioned symptoms associated with a viral infection. Later stages of the illness can involve the respiratory system and lead to increased work of breathing. These are often mistaken for asthma. Myocarditis can be distinguished as either fulminant or acute based on the severity of symptoms on presentation, as well as the time course over which symptoms develop and persist. This categorization can help predict the treatment, outcomes, and complications of myocarditis. Fulminant myocarditis is defined as sudden and severe myocarditis that is associated with signs and symptoms of heart failure while at rest. More specifically, fulminant myocarditis is characterized by a distinct, rapid onset of severe heart failure symptoms, such as shortness of breath and chest pain, that develop over the course of hours to days. Additionally, treatment requires the use of medications or mechanical devices to improve heart function. Acute non-fulminant myocarditis has a less distinct onset in contrast to fulminant myocarditis, and evolves over days to months. While the symptoms of acute myocarditis overlap with those of fulminant myocarditis, they do not typically occur at rest, and treatment does not require the use of mechanical circulatory support.
Causes While many causes of myocarditis are known, there are many cases in which a causative agent cannot be identified. In Europe and North America, viruses are common culprits. Worldwide, however, the most common cause is Chagas disease, an illness endemic to Central and South America that results from infection with the protozoan Trypanosoma cruzi. Overall, myocarditis can be caused by infections, immune conditions, toxins, drug reactions, and physical injuries to the heart.
Infections The most common causes of myocarditis are infectious organisms. Viral infections are the most common cause in developed countries, with a majority of cases being caused by those with single-stranded RNA genomes, such as Coxsackie viruses (especially Coxsackie B3 and B5). Globally, Chagas disease is the leading cause of myocarditis, which results from infection with the protozoan Trypanosoma cruzi. Bacteria can also result in myocarditis, although it is rare in patients with normal heart function and without a preexisting immunodeficiency. A list of the most relevant infectious organisms is below.
Viral: adenovirus, parvovirus B19, coxsackie virus, rubella virus, polio virus, Epstein–Barr virus, hepatitis C virus, influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2, causing COVID-19) Protozoan: Trypanosoma cruzi and Toxoplasma gondii (causing Chagas disease and toxoplasmosis, respectively) Bacterial: Brucella, Corynebacterium diphtheriae, Neisseria gonorrhoeae, Haemophilus influenzae, Actinomyces, Tropheryma whipplei, Vibrio cholerae, Borrelia burgdorferi, Leptospira, Rickettsia, Mycoplasma pneumoniae Fungal: Aspergillus Parasitic: Ascaris, Echinococcus granulosus, Paragonimus westermani, Schistosoma, Taenia solium, Trichinella spiralis, visceral larva migrans, Wuchereria bancrofti
Immune conditions Allergic reaction (e.g., to acetazolamide or amitriptyline) Kawasaki disease Autoimmunity (scleroderma, lupus, sarcoidosis, and systemic vasculitides) Toxic shock syndrome
Drug reactions and toxins Anthracyclines and other forms of chemotherapy Antipsychotics including clozapine Alcohol Stimulants such as mephedrone and cocaine Arsenic Carbon monoxide Snake venom Heavy metals (copper or iron)
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