Download Cardiovascular System Infection - Myocarditis

Cardiovascular System Infection - Myocarditis
Definition
 Myocarditis is inflammation of the heart muscle
(myocardium)
 It resembles a heart attack but coronary arteries are not
blocked
 Myocarditis is most often due to the infection by
 1- Common viruses, such as Parvovirus B19
 2- Non-viral pathogens (less commonly)


Borrelia burgdorferi (Lyme disease)
Trypanosoma cruzi (Chagas disease)
 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.
 Myocarditis may or may not include death (necrosis)
of heart tissue
 It may include 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
Dilated cardiomyopathy or DCM
 Gross pathology of idiopathic cardiomyopathy
 Opened left ventricle of heart shows a thickened, dilated left ventricle with
subendocardial fibrosis manifested as increased whiteness of endocardium
autopsy
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.
 Myocarditis is associated with an autoimmune reaction
 Streptococcal M protein and Coxsackie B virus have regions
(epitopes) that are similar to cardiac protein myosin
 M protein is a virulence factor that can be produced by
certain species of Streptococcus
 M protein is strongly anti-phagocytic protein and is a
major virulence factor
 Cross-reactivity of anti-M protein antibodies with heart
muscle is the basis for Rheumatic fever
 After the virus is gone, the immune system may attack
cardiac myosin
Causes of Myocarditis
 In Europe and North America, viruses are common cause
of myocarditis
 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
cruzi
 Transmission 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
Triatoma infestans
Photomicrograph of Giemsa-stained
Trypanosoma cruzi (CDC)
Trypansoma cruzi
parasite in a thin blood
smear (CDC Photo)
Rhodnius prolixus
Triatoma infestans
Rhodnius prolixus nymphs and adult
Panstrongylus geniculatus
Pathogenesis of Trypanosoma cruzi
 Human American trypanosomiasis, or Chagas disease, is a fatal
disease of humans
 The disease has two forms, a trypomastigote found in human
blood, and an amastigote found in tissues
 The acute form usually goes unnoticed and may present as a
localized swelling at the site of entry
 In the chronic stage, 10 to 20 years after infection, the parasite
invades the myofibrils of the heart causing myocarditis
 The gradual autoimmune destruction of heart myocardium lead
to cardiac enlargement and arrhythmias, and heart failure
Signs and symptoms
 The 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 vomiting
 The 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 heart
 About two thirds of people with chronic symptoms have cardiac
damage, including dilated cardiomyopathy, which causes heart
rhythm abnormalities and may result in sudden death
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 disease
Heart radiology Chagas disease
Toxoplasma gondii infection
 Toxoplasma 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 (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
Toxoplasma gondii Life cycle
Life cycle of T. gondii