Myocarditis
Myocarditis | |
---|---|
Other names | Inflammatory cardiomyopathy (infectious) |
Prognosis | Variable[3] |
Frequency | 2.5 million with cardiomyopathy (2015)[4] |
Deaths | 354,000 with cardiomyopathy (2015)[5] |
Myocarditis, also known as inflammatory cardiomyopathy, is an
Myocarditis is most often due to a
Treatment depends on both the severity and the cause.
In 2013, about 1.5 million cases of acute myocarditis occurred.[6] While people of all ages are affected, the young are most often affected.[7] It is slightly more common in males than females.[1] Most cases are mild.[2] In 2015 cardiomyopathy, including myocarditis, resulted in 354,000 deaths up from 294,000 in 1990.[8][5] The initial descriptions of the condition are from the mid-1800s.[9]
Signs and symptoms
The signs and symptoms associated with myocarditis are varied, and relate either to the actual inflammation of the
Symptoms | Notes | Signs | Notes |
---|---|---|---|
Chest pain | Often described as sharp or stabbing in nature | Fever | Especially when infectious, e.g., from parvovirus B19 |
Shortness of breath | Worse when lying down or in a prone position | Dull heart sounds | Muffling occurs with inflammation, especially with pericarditis |
Palpitations | Feeling like one's heart is beating forcefully | Abnormal heart rhythm | Determined using an electrocardiogram |
Dizziness or fainting | Can reflect inadequate blood flow to the brain | Damage to heart cells | Seen as elevated troponin and inflammation on imaging |
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.[11] 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.[12][11]
Children primarily present with the aforementioned symptoms associated with a viral infection.[10] Later stages of the illness can involve the respiratory system and lead to increased work of breathing. These are often mistaken for asthma.[10]
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.[13] 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.[13][14]
Acute non-fulminant myocarditis has a less distinct onset in contrast to fulminant myocarditis, and evolves over days to months.[14][15] 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.[15]
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.[16] 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.[10] Overall, myocarditis can be caused by infections, immune conditions, toxins, drug reactions, and physical injuries to the heart.[2] These different etiologies are detailed below.
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).[17][18] Globally, Chagas disease is the leading cause of myocarditis, which results from infection with the protozoan Trypanosoma cruzi.[10] Bacteria can also result in myocarditis, although it is rare in patients with normal heart function and without a preexisting immunodeficiency.[16][19] A list of the most relevant infectious organisms is below.
- Viral:
- Protozoan: Trypanosoma cruzi and Toxoplasma gondii (causing Chagas disease and toxoplasmosis, respectively)[10][24]
- 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
- Toxic shock syndrome
Drug reactions and toxins
- Anthracyclines and other forms of chemotherapy
- Antipsychotics including clozapine
- Alcohol
- Stimulants such as mephedrone and cocaine[26]
- Arsenic
- Carbon monoxide
- Snake venom
- Heavy metals (copper or iron)[2][27]
Vaccination
- Myocarditis and smallpox vaccine.[28]
- Myocarditis can be a rare side-effect of the Covid-19 FDA and European Medicines Agency estimates the risk of myocarditis after the Covid-19 vaccine as 1 case per 100,000 of those who are vaccinated.[29][30] The risk of myocarditis after Covid-19 vaccination was observed to be highest in males between 16–29 years of age, and after receiving the second dose of the mRNA Covid-19 vaccine.[31][32] For this high-risk group, incidence of myocarditis has been reported to be more than 1 case per 10,000.[33]
Physical injuries
- Electric shock
- Hyperpyrexia, and radiation
Mechanism
Most forms of myocarditis involve the infiltration of heart tissues by one or two types of pro-inflammatory blood cells,
The pathophysiology of viral myocarditis is not well understood, but it is believed to involve cardiotropic viruses (viruses with a high affinity for the heart muscle) gaining entry to cardiac muscle cells, usually via binding to a transmembrane receptor.
The binding of many types of
Diagnosis
Myocarditis refers to an underlying process that causes inflammation and injury of the heart. It does not refer to inflammation of the heart as a consequence of some other insult. Many secondary causes, such as a heart attack, can lead to inflammation of the myocardium and therefore the diagnosis of myocarditis cannot be made by evidence of inflammation of the myocardium alone.[36][37]
Myocardial inflammation can be suspected on the basis of elevated inflammatory markers including
Myocardial inflammation may also be suspected based on ECG findings, but these findings are not specific to myocarditis.[38] The ECG finding most commonly seen in myocarditis is sinus tachycardia with non-specific ST or T wave changes.[38] But other findings that may be seen in perimyocarditis (a combination of pericarditis and myocarditis) include PR segment depression, PR segment depression with associated ST segment elevation, diffuse ST segment elevation (in a pericarditis pattern).[38] ST segment elevation was seen in 62% of people with myocarditis.[29] The presence of Q waves, a widened QRS complex, prolongation of the QT interval, high degree AV nodal blockade, and ventricular tachyarrhythmias are associated with a poor prognosis when seen on ECG in people with myocarditis.[38]
The
Cardiac
-
Ultrasound showing cardiogenic shock due to myocarditis[42]
-
Ultrasound showing cardiogenic shock due to myocarditis[42]
-
Ultrasound showing cardiogenic shock due to myocarditis[42]
Treatment
While myocarditis has many etiologies and a variable constellation of signs and symptoms, many causes do not have a specific treatment thus the primary focus is on supportive care and symptom management.
In a majority of cases, the main therapies are used to support patients and are dependent on the severity of symptoms and the time course across which myocarditis develops.[15] Supportive therapies can be divided into two broad categories, medications and mechanical support.[45]
Medication
The specific medications that are used to support patients are directly related to the cause of the symptom or sign. Just as the symptoms of myocarditis mirror those of congestive heart failure, so too do the therapies.
Mechanical support
Mechanical support is used in cases of myocarditis in which medications alone do not lead to adequate heart function and the body requires additional support to achieve organ perfusion.
Prognosis
The prognosis associated with myocarditis is stratified by the severity and time course along which symptoms develop. In addition to symptom severity, there are also several indicators of heart function that can be used to predict patient outcomes, many of which are part of the standard evaluation of patients presenting with cardiovascular dysfunction. Most people with myocarditis have an uncomplicated, self-limited and mild course while making a full recovery.
An electrocardiogram is one of the most common screening tools used in cases of suspected cardiac pathology, such as myocarditis. The findings that correlate with poorer outcomes are non-specific and include widened QRS complexes and QT intervals, partial or complete atrial-ventricular heart block, and malignant ventricular arrhythmias like sustained ventricular tachycardia or ventricular fibrillation.[48] Electrocardiogram findings of ST elevations with upward concavity and an early repolarization pattern, however, were associated with a better cardiovascular prognosis in general.[48]
In cases of acute myocarditis, cardiac magnetic resonance imaging can reveal several prognostic indicators that, similar to ECGs, are non-specific and reflect poorer cardiac physiology. Late gadolinium enhancement on cardiac MRI demonstrates perturbations in extracellular volume as a result of cell necrosis or edema, and is significantly associated with increases in all-cause mortality, cardiovascular mortality, and major adverse cardiovascular events. The association was strongest with any late gadolinium enhancement, but remained true for findings of anterolateral-specific enhancement.[49][50] A similar relationship was found between a left ventricular ejection fraction < 50%, increased mortality, and increased major adverse cardiovascular events.[51]
Myocarditis has been reported to be a major cause of
In fulminant myocarditis, in which an inflammatory cytokine storm occurs, cardiac functions decline rapidly and the death rate is high.[14]
Epidemiology
The prevalence of myocarditis is estimated to be about 1-10 cases per 100,000 persons per year, with higher estimates at 22 cases per 100,000 persons annually.[29][53] The highest incidence of myocarditis is seen in men between the ages of 20 and 40.[29] Fulminant myocarditis, the most severe subtype, has been shown to occur in up to 2.5% of known myocarditis presentations. When looking at different causes of myocarditis, viral infection is the most prevalent, especially in children; however, the prevalence rate of myocarditis is often underestimated as the condition is easily overlooked and is sometimes asymptomatic.[53] Viral myocarditis being an outcome of viral infection depends heavily on genetic host factors and the pathogenicity unique to the virus.[54] If one tests positive for an acute viral infection, clinical developments have discovered that 1-5% of said population may show some form of myocarditis.[53]
In regard to the population affected, myocarditis is more common in pregnant women, children, and those who are immunocompromised.
Myocarditis is the third most common cause of death among young adults with a cumulative incidence rate globally of 1.5 cases per 100,000 persons annually.[55] Myocarditis accounts for approximately 20% of sudden cardiac death in a variety of populations, including adults under the age of 40, young athletes, United States Air Force recruits, and elite Swedish orienteers.[10] With individuals who develop myocarditis, the first year is difficult as a collection of cases have shown there is a 20% mortality rate.[13]
Myocarditis and COVID-19
Myocarditis can be seen during COVID-19, the disease caused by the SARS-CoV-2 virus;[58] with the myocarditis being associated with a spectrum of severities from asymptomatic to fulminant. The symptoms for myocarditis following a COVID-19 infection can present as chest pain, shortness of breath, fatigue, and irregular heartbeats which can make the accurate diagnosis of myocarditis challenging. [59] In one cohort study, comparing the autopsy reports of 277 hearts of people who died from COVID-19, clinically significant myocarditis was seen in approximately 2% of hearts.[23][60][61] Other estimates of the incidence of myocarditis in those with COVID-19 range from 2.4 cases of definite/probable myocarditis (based on clinical criteria) per 1,000 people with COVID-19 to 4.1 cases per 1,000 persons in those who are hospitalized with COVID-19.[29]
Although myocarditis is relatively rare in those with COVID-19, when it is present it is likely to follow a severe and fulminant course for those previously hospitalized with COVID-19. Of those with COVID-19 and myocarditis, 39% presented with severe myocarditis associated with hemodynamic instability, needing mechanical circulation support or other major interventions.[29] Severe myocarditis in COVID-19 is also more likely in those who have COVID-19 pneumonia.[29]
Myocarditis is a rare adverse side effect from mRNA COVID-19 vaccines.[62][63][64]
History
Cases of myocarditis have been documented as early as the 1600s,
Although myocarditis is clinically and pathologically clearly defined as "inflammation of the myocardium", its definition, classification, diagnosis, and treatment are subject to continued controversy, but endomyocardial biopsy has helped define the natural history of myocarditis and clarify clinicopathological correlations.[68]
See also
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