91. Myocarditis. Cardiomyopathies

Question 1

Myocarditis

Answer 1

Definition: primary inflammation of myocardium with necrosis of non-ischemic origin.

patho:

1. infections: mainly viral
   a. viral infections (coxsackieviruses A and B, and other enteroviruses HIV, adenovirus, hepatitis C)
   b. bacteria: borrelia burgdorferi
   c. parasites: trypanosoma cruzi
   d. helminth: trichinosis
2. non-infectious: immune mediated
   a. SLE
   b. Polymyositis
   c. hypersensitivity myocarditis: drug induced immune rxn

morphology:

• microscopically, edema in tissue with inflammatory cell infiltration
• giant cell myocarditis: fused macrophages- bad prognosis

complications: can be asymptomatic or have complications
1. heart failure
2. arrhythmia –> SCD
3. dilated cardiomyopathy

Question 2

Cardiomyopathy

Answer 2

definition: intrinsic cardiac muscle disease (non-ischemic and non-infective)
primary: confined to myocardium
secondary: cardiac manifestation of systemic disease

Question 3

Dilated cardiomyopathy

Answer 3

most common

definition: progressive cardiac dilation with systolic dysfunction, usually appears with hypertrophy cardiomyopathy

pathogenesis:
1. idiopathic
2. genetic inheritance
a. alpha-cardiac actin: encodes a protein that links
sarcomere to the cytoskeleton
b.dystrophin (x-linked): couples the intracellular
cytoskeleton to the ECM
3. acquired
a. myocarditis
b. alcoholism: alcohol and acetaldehyde have a direct toxic effect on myocardium
c. toxins: doxorubicin and cobalt
d. peripartum cardiomyopathy: multifactorial, hypetension associated pregnancy, gestational diabetes, VEGF anatgnoist secreted by placenta and anti-angiogenic cleavage products released during production of prolactin inhibits angiogenesis
e. iron overload: due to hereditary hemochromatosis or multiple transfusion; ROS production and injury

morphology:

1. 4 chambers dilation
2. hypertrophied myocytes that are stretched and irregular with some interstitial fibrosis

complication:

1. CHF
2. mural thrombi
3. arrhythmias
4. valve regurgitation

Question 4

Hypertrophic cardiomyopathy

Answer 4

definition: myocardial hypertrophy with systolic dysfunction. 1/3 of cases present with ventricular outflow obstruction.

what happens: contractility properties increased preserving systolic function, but relaxation does not occur leading to failure to fill the ventricle.

pathogenesis:
1. genetic inheritance:
a. autosomal dominant-missense mutation-gain of
function: affects sarcomeric proteins like beta-
myosin heavy chain and myosin binding protein C
and troponin T

morphology: myocardial hypertrophy (most IV septum) without ventricular dilation, myocyte disarray, interstitial fibrosis

complications

1. atrial fibrillation –> mural thrombi
2. ventricular fibrillation –> SCD
3. infectious endocarditis of mitral vavle
4. CHF

Question 5

restrictive cardiomyopathy

Answer 5

definition: decreased in ventricular compliance causing diastolic dysfunction

pathogenesis: mostly idiopathic
1. amyloidosis
a. systemic- AL multiple myeloma
b. local- senile cardiac amyloidosis, transthyretin
2. Hemochromatosis
3. secondary myocardial fibrosis after myocarditis or radiation therapy
4. endomyocardial fibrosis
a. fibrosis of ventricle endocardium and
subendocardium –> reduce compliance
b. cause: helminth infection (eosinophilia), nutritional
deficiency
5. Loeffler endomyocarditis
- exhibits endomyocardial fibrosis with addition of
mural thrombi

morphology:

• thickness and ventricles volume remain normal
• atrial dilation due to restrictive filling of ventricles