Lecture 13: Cardiomyopathies and Myocarditis
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17 terms
Terms | Definitions |
|---|---|
 Cardiomyopathy | Classic definition: development of congestive heart failure in the absence of coronary ratery disease, HTN, or valvular dysfunction - diagnosis of exclusion •CHF may be absent, CAD may be present, HTN & valve disease may co-exist •Myocardial Failure is NOT equivalent to Congestive heart failure Myocardial reserve can delay congestive heart failure Peripheral response to myocardial failure is congestive heart failure Definition: diffuse, irreversible myocardial damage (ex: necrosis, fibrosis, myocyte hypertrophy) leading to remodeling that may result in cardiac dysfunction (w/ or w/o) clinical CHF or arrhythmia •However, many cardiomyopathies may have minimal pathology yet still have high risk of arrhythmias |
| Dilated, congestive CM (DCM) | - Idiopathic, alcoholic, peripartum, AIDS, per-myocarditis, drug toxicity... Systolic dysfunction - global or segmental •One of the causes of congestive heart failure Diffuse, multifocal damage Cardiomegaly & myocyte hypertrophy Ventricular remodeling •Dilated chambers •Ventricular mural thinning •Annular dilation - mitral & tricuspid regurgitation Etiologies: •Majority - idiopathic Known causes: •Metabolism - deficient, antioxidant •Collagen - lupus, scleroderma... •Diabetes •Chronic HTN |
| Stages of cardiomyoatphy: | Hypertrophy - often w/o dysfunction •A this stage still relatively reversible Dilation (remodeling) - associated w/ increased EDV & EDP and increased wall stress (often w/ remodeling) •Mural (wall) thinning, slippage, ventricular cavity enlargement |
| DCM: Alcoholic | •Sever form, relative rare •Uncertain etiology •May occur in absence of cirrhosis •Similar morphology to other types of DCM but more severe dilation & remodeling •Dilated LV & end stage CHF |
| DCM: Peripartum | •Cardiomyopathy developing in last trimester to 6 months postpartum •Idiopathic but often associated w/ difficult pregnancy - allergic response? Antigens introduced by placental fetus? •~50% w/ myocarditis •Poor prognosis in diagnosed cases |
| DCM: AIDS | •Common in patients w/ end-stage AIDs •Etiology unknown but multi-factorial •Viral infection (not HIV), illicit drug use, other infection, treatment related Treatment related (e.g. AZT damages skeletal and cardiac muscle mitochondria) |
| Complications of DCM | CHF - nutmeg liver, Sudden Cardiac Death - arrhythmia Infarction due to embolized mural thrombi |
| Familial Hypertrophic CM: Beta Myosin Heavy Chain (MHC) | Mutation ofcontractile protein or associated proteins 2 major consequences: •CHF - diastolic & late stage systolic LV dysfunction & valvualr dysfunction •Sudden Cardiac Death - Arrhythmia 2 major types: ➢Mutations in beta myosin (MHC); Myosin - enzyme & structural protein ➢Mutation in Cardiac troponin T (cTNT) •No mutations in structural portion of protein; All mutations in motor or hinge area Autosomal dominant; Not X-linked; All mis-sense mutations Function: diastolic dysfunction w/ or w/o hypertrophy •Variable: LV outflow tract obstruction (w/systolic anterior motion of mitral valve), arrhythmia & sudden cardiac death •Can cause dilated cardiomyopathy or hypertrophic cardiomyopathy •Mitral valve regurgitation •Atypical chest pain (ischemia) •Congestive heart failure |
| Familial Hypertrophic CM:Beta Myosin Heavy Chain Defect | Structure: symmetric or asymmetric, global, intramyocardial vascular disease, pathologic fibrosis ->Asymmetricl septal hypetrophy - hallmark Intramyocardial vascular disease: Vascular sclerosis (fibromuscular hyperplasia) Pathologic fibrosis: "Contact" plaque (endocardial fibrosis) LV outflow tract ->Interstitial & replacement scarring Global hypertrophy Greatest percentage of collagen through LV compared to other cardiomyopathies Diastolic dysfunction but super normal EF - so good systolic, at least at beg. |
| Familial Hypertrophic CM: Histology | Disorganized myocardium & fibrosis ("whorls") Sclerotic intramyocardial coronary arteries |
| Beta myosin heavy chain mutations in FHM | •Autosomal dominant; Not X-linked; All mis-sense mutations •Often lethal poison polypeptide •Variable frequency of Sudden death •Frequent hypertrophy w/ or w/o obstruction |
| Mutation in Cardiac troponin T (cTNT): MHC vs. cTNT | MHC - phenotypic identification, actual frequency or artifact? •Missense mutations > 50 •Hypertrophy •variable sudden death •sudden death correlates w/ hypertrophy cTNT - phenotypic silence, sudden death, normal hearts •multiple mutations ~6 •rare hypertrophy •frequent sudden death •sudden death does NOT correlate w/ hypertrophy •worse prognosis than MHC |
| Ventricular Function in Cardiomyopathy: Systolic | Systolic Dysfunction ex: Congestive •Decreased ventricular contractility •Dilated ventricles w/ mural thinning •Globular heart w/ chamber dilation •Annular dilation w/ MR & TR •organ hypoperfusion •CHF symptoms - late •Elevated chamber filling pressure w/ subendocardial ischemia |
| Ventricular Function in Cardiomyopathy: Diastolic | Diastolic Dysfunction ex: hypetrophic & restrictive •Stiff LV w/ poor compliance •Mural hypertrophy •Small LV capacity - decreased stroke volume •Normal or supernormal ejection fraction •CHF symptoms |
| Cause of Familial Dilated Cardiomyopathy | Same Sarcomere Protein Genes that cause Hypertrophic Cardiomyopathy can cause Familial Dilated Cardiomyopathy |
| Myocarditis | Dallas criteria - pathologic definition of myocarditis Myocyte damage or necrosis w/ associated inflammation (lymphocytes, histiocytes, eosinophils, rarely neutrophils) NOT due to ischemia Rather than inflammatory cells REACTING to death of myocytes, here CAUSING death to myocytes Can be: Focal or multifocal Diffuse (fulminant): Diffuse, confluent necrosis & inflammation; often due to direct viral infection. Most often pediatric condition. Etiology •Most common: immune-mediated (may be triggered by prior viral infection) or idiopathic w/ multifocal myocyte necrosis & interstitial inflammation •Some viral (3-5%) ((coxsackie; adenovirus; cytomegalovirus; Ebstein-Barr; influenza) •Collagen-vascular disease •Generally in adults •Peripartum (usually eosinophils) •Parasites (toxoplasmosis; T. cruzi) •Granulomatous (e.g. sarcoidosis) |
| Types of Myocarditis [4] | Fulminant Allergic - eosinophils & lymphocytes Giant Cell myocarditis - syncytial giant cells in children, often secondary to direct viral infection Granulomatous Cocaine - not myocarditis ➢Cocaine-induced ischemic injury in myocardium, sharply demarcated area of necrosis w/ inflammation |
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