2 DefinitionMyocarditis is inflammation of the heart muscle (myocardium)It resembles a heart attack but coronary arteries are not blockedMyocarditis is most often due to the infection by1- Common viruses, such as Parvovirus B192- Non-viral pathogens (less commonly)Borrelia burgdorferi (Lyme disease)Trypanosoma cruzi (Chagas disease)
3 Myocarditis could be caused by 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.
4 Myocarditis may or may not include death (necrosis) of heart tissue It may include Dilated cardiomyopathyDilated cardiomyopathy or DCM is a condition in which the heart becomes weakened and enlarged, and cannot pump blood efficientlyThe decreased heart function can affect the lungs, liver, and other body systems
5 Dilated cardiomyopathy or DCM Gross pathology of idiopathic cardiomyopathyOpened left ventricle of heart shows a thickened, dilated left ventricle with subendocardial fibrosis manifested as increased whiteness of endocardium autopsy
6 Cellular infiltration and cardiac necrosis Histopathological image of myocarditis at autopsy in a patient with acute onset of congestive heart failure due to viral infection.
7 Myocarditis is associated with an autoimmune reaction Streptococcal M protein and Coxsackie B virus have regions (epitopes) that are similar to cardiac protein myosinM protein is a virulence factor that can be produced by certain species of StreptococcusM protein is strongly anti-phagocytic protein and is a major virulence factorCross-reactivity of anti-M protein antibodies with heart muscle is the basis for Rheumatic feverAfter the virus is gone, the immune system may attack cardiac myosin
8 Causes of MyocarditisIn Europe and North America, viruses are common cause of myocarditisWorldwide, 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 cruziTransmission of trypanosomiasis occurs when the Winged bug of the genus Triatoma deposits feces on the skin surface and subsequently bites; the human host then contaminating the bite area, with infected feces
9 Photomicrograph of Giemsa-stained Trypanosoma cruzi (CDC) Triatoma infestansPhotomicrograph of Giemsa-stained Trypanosoma cruzi (CDC)Trypansoma cruzi parasite in a thin blood smear (CDC Photo)
10 Rhodnius prolixusTriatoma infestansPanstrongylus geniculatusRhodnius prolixus nymphs and adult
11 Pathogenesis of Trypanosoma cruzi Human American trypanosomiasis, or Chagas disease, is a fatal disease of humansThe disease has two forms, a trypomastigote found in human blood, and an amastigote found in tissuesThe acute form usually goes unnoticed and may present as a localized swelling at the site of entryIn the chronic stage, 10 to 20 years after infection, the parasite invades the myofibrils of the heart causing myocarditisThe gradual autoimmune destruction of heart myocardium lead to cardiac enlargement and arrhythmias, and heart failure
13 Signs and symptomsThe acute phase lasts for the first few weeks or months of infection. Mild symptoms can include fever, fatigue , headache, rash, loss of appetite, diarrhea, and vomitingThe signs on physical examination can include mild enlargement of the liver or spleen, swollen glands, and local swelling (a chagoma) where the parasite entered the body The symptomatic chronic stage affects the nervous system, digestive system, and heartAbout two thirds of people with chronic symptoms have cardiac damage, including dilated cardiomyopathy, which causes heart rhythm abnormalities and may result in sudden death
14 Cardiac muscle pathology; Chagas disease Romaña's sign, the swelling of the child's eyelid, is a marker of acute Chagas disease. The swelling is due to bug feces being accidentally rubbed into the eye, or because the bite wound was on the same side of the child's face as the swelling. Photo courtesy of WHO/TDR.Heart pathology Chagas diseaseHeart radiology Chagas disease
15 Toxoplasma gondii infection Toxoplasma gondii is a species of parasitic protozoa in the genus ToxoplasmaThe definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals (birds or mammals, including humans)Toxoplasmosis, the disease of which T. gondii is the causative agent, is usually minor and self-limiting but can have serious or fatal effects on a fetus whose mother first contracts the disease during pregnancy or on an immunocompromised human