Myocarditis
Encyclopedia
Myocarditis is inflammation
of heart muscle (myocardium). It resembles a heart attack but coronary arteries are not blocked.
Myocarditis is most often due to infection
by common virus
es, such as parvovirus B19
, less commonly non-viral pathogens such as Borrelia burgdorferi
(Lyme disease) or Trypanosoma cruzi
, or as a hypersensitivity response to drugs.
The definition of myocarditis varies, but the central feature is an infection of the heart, with an inflammatory infiltrate, and damage to the heart muscle, without the blockage of coronary arteries that define a heart attack (myocardial infarction
) or other common non-infectious causes. Myocarditis may or may not include death (necrosis
) of heart tissue. It may include dilated cardiomyopathy
.
Myocarditis is often an autoimmune reaction. Streptococcal M protein
and coxsackievirus
B have regions (epitope
s) that are immunologically similar to cardiac myosin
. After the virus is gone, the immune system may attack cardiac myosin.
Because a definitive diagnosis requires a heart biopsy, which doctors are reluctant to do because they are invasive, statistics on the incidence of myocarditis vary widely.
The consequences of myocarditis thus also vary widely. It can cause a mild disease without any symptoms that resolves itself, or it may cause chest pain, heart failure, or sudden death. An acute myocardial infarction-like syndrome with normal coronary arteries has a good prognosis. Heart failure, even with dilated left ventricle
, may have a good prognosis. Ventricular arrhythmias and high-degree heart block have a poor prognosis. Loss of right ventricular function is a strong predictor of death.
Since myocarditis is often due to a viral illness, many patients give a history of symptoms consistent with a recent viral infection, including fever, rash, diarrhea, joint pains, and easy fatigueability.
Myocarditis is often associated with pericarditis
, and many patients present with signs and symptoms that suggest concurrent myocarditis and pericarditis.
.
Bacterial myocarditis is rare in patients without immunodeficiency
.
Myocardial inflammation can be suspected on the basis of electrocardiographic
results (ECG), elevated C-reactive protein
(CRP) and/or Erythrocyte sedimentation rate
(ESR) and increased IgM
(serology
) against viruses known to affect the myocardium. Markers of myocardial damage (troponin
or creatine kinase
cardiac isoenzymes) are elevated.
The electrocardiogram
(ECG) findings most commonly seen in myocarditis are diffuse T wave
inversions; saddle-shaped ST-segment elevations may be present (these are also seen in pericarditis).
The gold standard
is still biopsy
of the myocardium, generally done in the setting of angiography. A small tissue sample of the endocardium
and myocardium is taken, and investigated by a pathologist by light microscopy and—if necessary—immunochemistry
and special staining methods. Histopathological features are: myocardial interstitium with abundant edema and inflammatory infiltrate, rich in lymphocyte
s and macrophage
s. Focal destruction of myocytes explains the myocardial pump failure.
Cardiac magnetic resonance imaging
(cMRI or CMR) has been shown to be very useful in diagnosing myocarditis by visualizing markers for inflammation
of the myocardium.
Recently, consensus criteria for the diagnosis of myocarditis by CMR have been published
In the acute phase, supportive therapy including bed rest is indicated. For symptomatic patients, digoxin
and diuretic
s provide clinical improvement. For patients with moderate to severe dysfunction, cardiac function can be supported by use of inotrope
s such as Milrinone in acute phase followed by oral therapy with ACE inhibitor
s (Captopril, Lisinopril) when tolerated. People who do not respond to conventional therapy are candidates for bridge therapy with left ventricular assist device
s (LVADs). Heart transplantation
is reserved for patients who fail to improve with conventional therapy.
In several small case series and randomized control trials, systemic corticosteroids have shown to have beneficial effects in patients with proven myocarditis. However, data on the usefulness of corticosteroids should be interpreted with caution since 58% of adults recover spontaneously while most studies on children and infants lack control groups.
, 1–9% of all patients had evidence of myocardial inflammation. In young adults, up to 20% of all cases of sudden death are due to myocarditis.
Among patients with HIV, myocarditis is the most common cardiac pathological finding at autopsy
, with a prevalence of 50% or more.
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of heart muscle (myocardium). It resembles a heart attack but coronary arteries are not blocked.
Myocarditis is most often due to infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
by common virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es, such as parvovirus B19
Parvovirus B19
The B19 virus, generally referred to as parvovirus B19 or sometimes erythrovirus B19, was the first known human virus in the family of parvoviruses, genus erythrovirus...
, less commonly non-viral pathogens such as Borrelia burgdorferi
Borrelia burgdorferi
Borrelia burgdorferi is a species of Gram negative bacteria of the spirochete class of the genus Borrelia. B. burgdorferi is predominant in North America, but also exists in Europe, and is the agent of Lyme disease....
(Lyme disease) or Trypanosoma cruzi
Trypanosoma cruzi
Trypanosoma cruzi is a species of parasitic euglenoid trypanosomes. This species causes the trypanosomiasis diseases in humans and animals in America...
, or as a hypersensitivity response to drugs.
The definition of myocarditis varies, but the central feature is an infection of the heart, with an inflammatory infiltrate, and damage to the heart muscle, without the blockage of coronary arteries that define a heart attack (myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
) or other common non-infectious causes. Myocarditis may or may not include death (necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
) of heart tissue. It may include dilated cardiomyopathy
Dilated cardiomyopathy
Dilated cardiomyopathy or DCM is a condition in which the heart becomes weakened and enlarged and cannot pump blood efficiently. The decreased heart function can affect the lungs, liver, and other body systems....
.
Myocarditis is often an autoimmune reaction. Streptococcal M protein
M protein (Streptococcus)
M protein is a virulence factor that can be produced by certain species of Streptococcus.Viruses, parasites and bacteria are covered in protein and sugar molecules that help them gain entry into a host by counteracting the host's defences. One such molecule is the M protein produced by certain...
and coxsackievirus
Coxsackievirus
Coxsackievirus is a virus that belongs to a family of non enveloped linear positive-sense ssRNA viruses, Picornaviridae and the genus Enterovirus, which also includes poliovirus and echovirus. Enteroviruses are among the most common and important human pathogens and ordinarily its members are...
B have regions (epitope
Epitope
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that recognizes the epitope is called a paratope...
s) that are immunologically similar to cardiac myosin
Myosin
Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...
. After the virus is gone, the immune system may attack cardiac myosin.
Because a definitive diagnosis requires a heart biopsy, which doctors are reluctant to do because they are invasive, statistics on the incidence of myocarditis vary widely.
The consequences of myocarditis thus also vary widely. It can cause a mild disease without any symptoms that resolves itself, or it may cause chest pain, heart failure, or sudden death. An acute myocardial infarction-like syndrome with normal coronary arteries has a good prognosis. Heart failure, even with dilated left ventricle
Left ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
, may have a good prognosis. Ventricular arrhythmias and high-degree heart block have a poor prognosis. Loss of right ventricular function is a strong predictor of death.
Signs and symptoms
The signs and symptoms associated with myocarditis are varied, and relate either to the actual inflammation of the myocardium, or the weakness of the heart muscle that is secondary to the inflammation. Signs and symptoms of myocarditis include:- Chest painChest painChest pain may be a symptom of a number of serious conditions and is generally considered a medical emergency. Even though it may be determined that the pain is non-cardiac in origin, this is often a diagnosis of exclusion made after ruling out more serious causes of the pain.-Differential...
(often described as "stabbing" in character) - Congestive heart failureCongestive heart failureHeart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
(leading to edemaEdemaEdema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
, breathlessness and hepaticLiverThe liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
congestion) - PalpitationPalpitationA palpitation is an abnormality of heartbeat that causes a conscious awareness of its beating, whether it is too slow, too fast, irregular, or at its normal frequency. The word may also refer to this sensation itself...
s (due to arrhythmias) - Sudden death (in young adults, myocarditis causes up to 20% of all cases of sudden death)
- Fever (especially when infectious, e.g. in rheumatic feverRheumatic feverRheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after...
) - Symptoms in infants and toddlers tend to be more non-specific with generalized malaise, poor appetite, abdominal pain, chronic cough. Later stages of the illness will present with respiratory symptoms with increased work of breathing and is often mistaken for asthma.
Since myocarditis is often due to a viral illness, many patients give a history of symptoms consistent with a recent viral infection, including fever, rash, diarrhea, joint pains, and easy fatigueability.
Myocarditis is often associated with pericarditis
Pericarditis
Pericarditis is an inflammation of the pericardium . A characteristic chest pain is often present.The causes of pericarditis are varied, including viral infections of the pericardium, idiopathic causes, uremic pericarditis, bacterial infections of the precardium Pericarditis is an inflammation of...
, and many patients present with signs and symptoms that suggest concurrent myocarditis and pericarditis.
Causes
A large number of causes of myocarditis have been identified, but often a cause cannot be found. 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 is due to infection by the protozoan Trypanosoma cruziTrypanosoma cruzi
Trypanosoma cruzi is a species of parasitic euglenoid trypanosomes. This species causes the trypanosomiasis diseases in humans and animals in America...
.
Infections
- ViralVirusA virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
(Parvovirus B19Parvovirus B19The B19 virus, generally referred to as parvovirus B19 or sometimes erythrovirus B19, was the first known human virus in the family of parvoviruses, genus erythrovirus...
, Coxsackie virus, HIVHIVHuman immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
, enterovirusEnterovirusEnteroviruses are a genus of ssRNA viruses associated with several human and mammalian diseases. Serologic studies have distinguished 66 human enterovirus serotypes on the basis of antibody neutralization tests. Additional antigenic variants have been defined within several of the serotypes on the...
, rubella virusRubella virusRubella virus is the pathogenic agent of the disease Rubella, and is the cause of congenital rubella syndrome when infection occurs during the first weeks of lunacy.Humans are the only known host of this virus....
, polio virus, cytomegalovirusCytomegalovirusCytomegalovirus is a viral genus of the viral group known as Herpesviridae or herpesviruses. It is typically abbreviated as CMV: The species that infects humans is commonly known as human CMV or human herpesvirus-5 , and is the most studied of all cytomegaloviruses...
, human herpesvirus 6 and possibly hepatitis CHepatitis CHepatitis C is an infectious disease primarily affecting the liver, caused by the hepatitis C virus . The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years...
) - Protozoan (Trypanosoma cruziTrypanosoma cruziTrypanosoma cruzi is a species of parasitic euglenoid trypanosomes. This species causes the trypanosomiasis diseases in humans and animals in America...
causing Chagas diseaseChagas diseaseChagas disease is a tropical parasitic disease caused by the flagellate protozoan Trypanosoma cruzi. T. cruzi is commonly transmitted to humans and other mammals by an insect vector, the blood-sucking insects of the subfamily Triatominae most commonly species belonging to the Triatoma, Rhodnius,...
and Toxoplasma gondiiToxoplasma gondiiToxoplasma gondii is a species of parasitic protozoa in the genus Toxoplasma. The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals . Toxoplasmosis, the disease of which T...
) - BacteriaBacteriaBacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l (brucellaBrucellosisBrucellosis, also called Bang's disease, Crimean fever, Gibraltar fever, Malta fever, Maltese fever, Mediterranean fever, rock fever, or undulant fever, is a highly contagious zoonosis caused by ingestion of unsterilized milk or meat from infected animals or close contact with their secretions...
, Corynebacterium diphtheriaeCorynebacterium diphtheriaeCorynebacterium diphtheriae is a pathogenic bacterium that causes diphtheria. It is also known as the Klebs-Löffler bacillus, because it was discovered in 1884 by German bacteriologists Edwin Klebs and Friedrich Löffler .-Classification:Four subspecies are recognized: C. diphtheriae mitis, C....
, gonococcus, Haemophilus influenzaeHaemophilus influenzaeHaemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
, ActinomycesActinomycesActinomyces from Greek "actino" that means mucus and fungus, is a genus of the actinobacteria class of bacteria. They are all Gram-positive and are characterized by contiguous spread, suppurative and granulomatous inflammation, and formation of multiple abscesses and sinus tracts that may...
, Tropheryma whippleiWhipple's diseaseWhipple's disease is a rare, systemic infectious disease caused by the bacterium Tropheryma whipplei. First described by George Hoyt Whipple in 1907 and commonly considered a gastrointestinal disorder, Whipple's disease primarily causes malabsorption but may affect any part of the body including...
, Vibrio choleraeVibrio choleraeVibrio cholerae is a Gram-negative, comma-shaped bacterium. Some strains of V. cholerae cause the disease cholera. V. cholerae is facultatively anaerobic and has a flagella at one cell pole. V...
, Borrelia burgdorferiBorrelia burgdorferiBorrelia burgdorferi is a species of Gram negative bacteria of the spirochete class of the genus Borrelia. B. burgdorferi is predominant in North America, but also exists in Europe, and is the agent of Lyme disease....
, leptospirosisLeptospirosisLeptospirosis is caused by infection with bacteria of the genus Leptospira, and affects humans as well as other mammals, birds, amphibians, and reptiles.The...
, RickettsiaRickettsiaRickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...
) - FungalFungusA fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
(aspergillusAspergillusAspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli...
) - Parasitic (ascarisAscarisAscaris is a genus of parasitic nematode worms known as the "giant intestinal roundworms". One species, A. suum, typically infects pigs, while another, A. lumbricoides, affects human populations, typically in sub-tropical and tropical areas with poor sanitation. A...
, Echinococcus granulosusEchinococcus granulosusEchinococcus granulosus, also called the Hydatid worm or Hyper Tape-worm, is a cyclophyllid cestode that parasitizes the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and humans, where it causes hydatid disease...
, Paragonimus westermaniParagonimus westermaniParagonimus westermani is a lung fluke and is most prominent in Asia and South America. It was discovered from two Bengal tigers that died in zoos in Europe in 1878...
, schistosomaSchistosomaA genus of trematodes, Schistosoma, commonly known as blood-flukes and bilharzia, includes flatworms which are responsible for a highly significant parasitic infection of humans by causing the disease schistosomiasis, and are considered by the World Health Organization as the second most...
, Taenia solium, Trichinella spiralisTrichinella spiralisTrichinella spiralis is a nematode parasite, occurring in rats, pigs, bears and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in undercooked pork products...
, visceral larva migrans, and Wuchereria bancroftiWuchereria bancroftiFilaria, is a parasitic filarial nematode spread by a mosquito vector. It is one of the three parasites that cause lymphatic filariasis, an infection of the lymphatic system by filarial worms. It affects over 120 million people, primarily in Africa, South America, and other tropical and...
)
Bacterial myocarditis is rare in patients without immunodeficiency
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...
.
Toxins
- DrugsMedicationA pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
(ethanolEthanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
, anthracyclineAnthracyclineAnthracyclines are a class of drugs used in cancer chemotherapy derived from Streptomyces bacterium Streptomyces peucetius var...
s and some other forms of chemotherapyChemotherapyChemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
, and antipsychoticAntipsychoticAn antipsychotic is a tranquilizing psychiatric medication primarily used to manage psychosis , particularly in schizophrenia and bipolar disorder. A first generation of antipsychotics, known as typical antipsychotics, was discovered in the 1950s...
s, e.g. clozapineClozapineClozapine is an antipsychotic medication used in the treatment of schizophrenia, and is also used off-label in the treatment of bipolar disorder. Wyatt. R and Chew...
, also some designer drugDesigner drugDesigner drug is a term used to describe drugs that are created to get around existing drug laws, usually by preparing analogs or derivatives of existing drugs by modifying their chemical structure to varying degrees, or less commonly by finding drugs with entirely different chemical structures...
s such as mephedrone)
Immunologic
- AllergicAllergyAn Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...
(acetazolamideAcetazolamideAcetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, Idiopathic intracranial hypertension , altitude sickness, cystinuria, and dural ectasia...
, amitriptylineAmitriptylineAmitriptyline is a tricyclic antidepressant . It is the most widely used TCA and has at least equal efficacy against depression as the newer class of SSRIs...
) - Rejection after a heart transplant
- Autoantigens (sclerodermaSclerodermaSystemic sclerosis or systemic scleroderma is a systemic autoimmune disease or systemic connective tissue disease that is a subtype of scleroderma.-Skin symptoms:...
, systemic lupus erythematosis, sarcoidosisSarcoidosisSarcoidosis , also called sarcoid, Besnier-Boeck disease or Besnier-Boeck-Schaumann disease, is a disease in which abnormal collections of chronic inflammatory cells form as nodules in multiple organs. The cause of sarcoidosis is unknown...
, systemic vasculitisVasculitisVasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
such as Churg-Strauss syndromeChurg-Strauss syndromeChurg–Strauss syndrome is a medium and small vessel autoimmune vasculitis, leading to necrosis. It involves mainly the blood vessels of the lungs , gastrointestinal system, and peripheral nerves, but also affects the heart, skin and kidneys. It is a rare disease that is non-inheritable and...
, Wegener's granulomatosisWegener's granulomatosisWegener's granulomatosis , more recently granulomatosis with polyangiitis , is an incurable form of vasculitis that affects the nose, lungs, kidneys and other organs. Due to its end-organ damage, it is life-threatening and requires long-term immunosuppression...
) - ToxinToxinA toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
s (arsenicArsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, toxic shock syndrome toxinToxic shock syndrome toxinToxic Shock Syndrome Toxin is a superantigen with a size of 22KDa produced by somewhere between 5% and 25% of Staphylococcus aureus isolates. It causes toxic shock syndrome by stimulating the release of large amounts of interleukin-1, interleukin-2 and tumour necrosis factor...
, carbon monoxideCarbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
, snake venomSnake venomSnake venom is highly modified saliva that is produced by special glands of certain species of snakes. The glands which secrete the zootoxin are a modification of the parotid salivary gland of other vertebrates, and are usually situated on each side of the head below and behind the eye,...
) - Heavy metalsHeavy metalsA heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight,...
(copperCopperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, ironIronIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
)
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 can not be made by evidence of inflammation of the myocardium alone.Myocardial inflammation can be suspected on the basis of electrocardiographic
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
results (ECG), elevated C-reactive protein
C-reactive protein
C-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
(CRP) and/or Erythrocyte sedimentation rate
Erythrocyte sedimentation rate
The erythrocyte sedimentation rate , also called a sedimentation rate or Biernacki Reaction, is the rate at which red blood cells sediment in a period of 1 hour...
(ESR) and increased IgM
IGM
IGM as an acronym or abbreviation can refer to:* Immunoglobulin M , the primary antibody against A and B antigens on red blood cells* International Grandmaster, a chess ranking* intergalactic medium* Intragroup medium - see: Intracluster medium...
(serology
Serology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...
) against viruses known to affect the myocardium. Markers of myocardial damage (troponin
Troponin
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the human cardiac troponin core complex in the calcium-saturated form...
or creatine kinase
Creatine kinase
Creatine kinase , also known as creatine phosphokinase or phospho-creatine kinase , is an enzyme expressed by various tissues and cell types. CK catalyses the conversion of creatine and consumes adenosine triphosphate to create phosphocreatine and adenosine diphosphate...
cardiac isoenzymes) are elevated.
The electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG) findings most commonly seen in myocarditis are diffuse T wave
T wave
In electrocardiography, the T wave represents the repolarization of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period. The last half of the T wave is referred to as the relative refractory period...
inversions; saddle-shaped ST-segment elevations may be present (these are also seen in pericarditis).
The gold standard
Gold standard (test)
In medicine and statistics, gold standard test refers to a diagnostic test or benchmark that is the best available under reasonable conditions. It does not have to be necessarily the best possible test for the condition in absolute terms...
is still biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
of the myocardium, generally done in the setting of angiography. A small tissue sample of the endocardium
Endocardium
The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the endothelial cells that line blood vessels....
and myocardium is taken, and investigated by a pathologist by light microscopy and—if necessary—immunochemistry
Immunochemistry
Immunochemistry is a branch of chemistry that involves the study of the reactions and components on the immune system.Various methods in immunochemistry have been developed and refined, and been used in scientific study, from virology to molecular evolution....
and special staining methods. Histopathological features are: myocardial interstitium with abundant edema and inflammatory infiltrate, rich in lymphocyte
Lymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
s and macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s. Focal destruction of myocytes explains the myocardial pump failure.
Cardiac magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(cMRI or CMR) has been shown to be very useful in diagnosing myocarditis by visualizing markers for inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the myocardium.
Recently, consensus criteria for the diagnosis of myocarditis by CMR have been published
Treatment
As most viral infections cannot be treated with directed therapy, symptomatic treatment is the only form of therapy for those forms of myocarditis.In the acute phase, supportive therapy including bed rest is indicated. For symptomatic patients, digoxin
Digoxin
Digoxin INN , also known as digitalis, is a purified cardiac glycoside and extracted from the foxglove plant, Digitalis lanata. Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin...
and diuretic
Diuretic
A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...
s provide clinical improvement. For patients with moderate to severe dysfunction, cardiac function can be supported by use of inotrope
Inotrope
An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions...
s such as Milrinone in acute phase followed by oral therapy with ACE inhibitor
ACE inhibitor
ACE inhibitors or angiotensin-converting enzyme inhibitors are a group of drugs used primarily for the treatment of hypertension and congestive heart failure...
s (Captopril, Lisinopril) when tolerated. People who do not respond to conventional therapy are candidates for bridge therapy with left ventricular assist device
Ventricular assist device
A Ventricular assist device, or VAD, is a mechanical circulatory device that is used to partially or completely replace the function of a failing heart...
s (LVADs). Heart transplantation
Heart transplantation
A heart transplant, or a cardiac transplantation, is a surgical transplant procedure performed on patients with end-stage heart failure or severe coronary artery disease. As of 2007 the most common procedure was to take a working heart from a recently deceased organ donor and implant it into the...
is reserved for patients who fail to improve with conventional therapy.
In several small case series and randomized control trials, systemic corticosteroids have shown to have beneficial effects in patients with proven myocarditis. However, data on the usefulness of corticosteroids should be interpreted with caution since 58% of adults recover spontaneously while most studies on children and infants lack control groups.
Epidemiology
The exact incidence of myocarditis is unknown. However, in series of routine autopsiesAutopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...
, 1–9% of all patients had evidence of myocardial inflammation. In young adults, up to 20% of all cases of sudden death are due to myocarditis.
Among patients with HIV, myocarditis is the most common cardiac pathological finding at autopsy
Autopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...
, with a prevalence of 50% or more.