6: Cardiomyopathy, Myocarditis, Pericarditis, CHD Flashcards
what is: Heterogeneous group of disease associated with mechanical/electrical dysfunction usually exhibiting inappropriate ventricular hypertrophy or dilatation
CARDIOMYOPATHY
3 types of cardiomyopathy;
which is most common?
- dilated** (most common, 90% of cases)
- hypertrophic
- restrictive
dilated cardiomyopathy:
define, epidemiology
- Progressive cardiac dilation and contractile dysfunction, usually with hypertrophy
- Epi:
- Usually diagnosed at end-stage
- **Most common (90% of cases)
what are the acquired causes of dilated cardiomyopathy?
- Myocarditis
- TOXICITIES ( alcohol, chemotherapy - doxorubicin, cobalt ingestion)
- Pregnancy (peripartum cardiomyopathy – late pregnancy or months postpartum)
- Stress-provoked – persistent tachycardia, hyperthyroidism
- Iron overload – hereditary hemochromatosis, multiple transfusions
how many cases of dilated cardiomyopathy are due to genetic causes?
what are the genetic causes?
- Genetic causes (20-50% of cases)
- causes
- >50 genes have been implicated
- Autosomal dominant most common
- Most common mutations affect cytoskeletal proteins (desmin) / proteins linking sarcomere to cytoskeleton (α-cardiac actin)
- X-linked – mutations in dystrophin
Clinical features of Dilated Cardiomyopathy
- Typical pt: dx b/w 20-50 years
-
Dyspnea, easy fatigability
- Over half die within 2 years
- Ineffective contraction –> low ejection fraction (<25% at end stage)
- Secondary mitral regurgitation
- Embolism
- Cardiac arrhythmias
gross anatomical changes w/ DILATED CARDIOMYOPATHY?
- Heart enlarges 2-3x normal
- Flabby (all chambers are dilated)
- Mural thrombi often present - source of thromboemboli
what are the microscopic/ histological changes associated with DILATED CARDIOMYOPATHY?
- myocyte hypertrophy with enlarged nuclei OR
- Attenuated myocytes that are stretched out
- interstitial fibrosis
what are the causes of ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY?
- Autosomal dominant – genes encoding desmosomal junctional proteins (plakoglobin) and proteins that interact with desmosomes (desmin)
- Right-sided HF and rhythm disturbances
- Cause of sudden cardiac death
- Right ventricular wall is severely thinned (fatty replacement and fibrosis)
- Left-sided involvement may occur
HYPERTROPHIC CARDIOMYOPATHY:
what is the pathological change, and what aspect of heart function does this affect?
- Change: Thick-walled, heavy, hypercontractile heart
- Effect: Defective compliance/ diastolic filling and ventricular outflow obstruction (1/3rd of cases)
More rare, incidence is 1 in 500
what is the pathogenesis of Hypertrophic Cardiomyopathy?
(hint: autosomal dominant pathology)
-
Missense mutations in genes encoding sarcomeric proteins –> hypertrophic cardiomyopathy
- >400 mutations in 9 genes
-
β-myosin heavy chain > myosin-binding protein C and troponin T
- 70-80% of all cases
what are the gross anatomical changes in hypertrophic cardiomyopathy?
- Massive myocardial hypertrophy w/o ventricular dilation
- Ventricular septum > left ventricular free wall (asymmetric septal hypertrophy)
- Small, banana-like configuration of LV cavity
- LV outflow tract w/ fibrous endocardial plaque
- Anterior mitral leaflet is thickened -> Make contact with each other during ventricular systole
what are the microscopic changes in hypertrophic cardiomyopathy?
- massive myocyte hypertrophy
- haphazardly arranged bundles of myocytes
- interstitial fibrosis
will patients with hypertrophic cardiomyopathy have a family hx of the same condition?
YES; pts will likely have family history of cardiac dysfunction causing death;
this is an autosomal dominant condition caused by missense mutations in genes encoding sarcomeric proteins
which type of cardiomyopathy is associated w/ SUDDEN DEATH IN ATHLETES?
HYPERTROPHIC CARDIOMYOPATHY;
Sudden death - cause of death for 1/3rd of athletes under 35 years
what factors of hypertrophic cardiomyopathy lead to focal myocardial ischmia?
- massive hypertrophy
- high LV chamber pressure
- compromised intramural arteries
clinical features of hypertrophic cardiomyopathy?
- Exertional dyspnea (from compromised cardiac output)
- Harsh systolic ejection murmur
- Focal myocardial ischemia
And sudden cardiac death in athletes
define: sudden cardiac death
(hint: timing/sxs)
Unexpected death from cardiac causes either:
- without symptoms or
- within 1-24 hours of symptom onset
what disease accounts for 80-90% of cases of sudden cardiac death?
CORONARY ARTERY DISEASE (CAD)
what is the mechanism that causes most cases of sudden cardiac death?
most often due to a lethal arrhythmia (asystole/V. f i b )
typical patient and predisposing factors for sudden cardiac death?
- younger victims
- factors:
- Hereditary or acquired abnormalities of cardiac conduction system/coronary arteries
- Myocarditis
- Cardiomyopathies
- Pulmonary hypertension
- Drugs
restrictive cardiomyopathy:
effect on cardiac function
Decrease in ventricular compliance –> impaired ventricular filling during diastole
restrictive cardiomyopathy:
pathogenesis
- Idiopathic, or
- Associated with systemic disease (radiation fibrosis, amyloidosis, sarcoidosis, metastatic tumors, inborn errors of metabolism), or
- Slightly enlarged
restrictive cardiomyopathy:
morphology
- not distinctive
- ventricles can be normal-sized, or slightly enlarged
- myocardium is firm and non-compliant
- bilateral dilation is common
what is: the deposition of extracellular proteins (insoluble beta-pleated sheets)
amyloidosis
pathogenesis of amyloidosis?
- due systemic disesae (myleoma), OR
- restricted to heart (senile cardiac amyloidosis)
what is amyloid composed of?
epidemiology of pts who carry mutation in this?
- transthyretin (amyloid is composed of transthyretin)
- 4% of african americans carry mutation in transthyretin
how to stain/visualize amyloidosis?
amorphous deposition –> can be seen w/ congo red & polarized light
–> apple-green birefringence
(think: “Amy Loid” eating an “Apple Green” in Congo Red?)
Organisms can cause direct injury or immune response against virally infected cells causes myocardial injury.
WHAT IS MOST COMMON CAUSE OF MYOCARDITIS IN US?
Viruses;
Coxsackievirus A & B
In addition to viruses, what were the other INFECTIVE causes of myocarditis emphasized in class?
- Bacteria (diphtheria toxin released by Corynebacterium causes injury)
- Lyme disease (self-limited conduction system disorder – may require pacemaker)
- Chagas disease (in S. America)
define: chagas disease
American trypanosomiasis, is a tropical parasitic disease caused by the protist Trypanosoma cruzi;
Sxs: an be mild, causing swelling and fever, or it can be long lasting.
Sequelae: Left untreated, it can cause congestive heart failure.
Myocarditis can result from Infective, Immune-Mediated Reactions, and Unknown causes:
What are the Immune-Mediated Reactions?
aka Hypersensitivity Myocarditis:
- Postviral
- Poststreptococcal (rheumatic fever)
- Systemic lupus erythematous
- Drug hypersensitivity (e.g. methyldopa, sulfonamides)
- Transplant rejection
Myocarditis can result from Infective, Immune-Mediated Reactions, and Unknown causes:
What are the Unknown causes (those that don’t fit under infected or immune mediated)?
- Sarcoidosis
- Giant Cell myocarditis
gross morphology of myocarditis
- Heart can appear normal, OR
- flabby with mural thrombi (advanced stages)