SM02 Mini1 Flashcards
(52 cards)
what are the subtypes of cardiomyopathy?
- hypertrophic
- dilated
- glycogen
- restrictive
- arrhythmogenic right ventricular
cause of hypertrophic cardiomyopathy
dz of sarcomere
thickening of cardiomyocyte due to hypersensitivity to ATP or Ca2+
presentation of hypertrophic cardiomyopathy
increased ventricular wall thickness
cardiac hypertrophy in absence of increased external load
preserved systolic function
impaired diastolic function
septum predominant site of involvement
most frequent genetic mutations in familial hypertrophic cardiomyopathy?
- beta-myosin heavy chain
- part of myosin motor unit
- frequency= 35-50%
- cardiac troponin T
- anchors troponins to tropomyosin
- frequency= 15-20%
- cardiac myosin-binding protein C
- anchors myosin to titin
- frequency= 15-20%
presentation of dilated cardiomyopathy (DCM)
left ventricular chamber enlargement & systolic dysfunction
normal or modest increase in ventricular wall thickness
genetics of dilated cardiomyopathy
**affected proteins function to transmit force generated during contraction**
dz of cardiac cytoskeleton
cause sarconere to contract w/less force
35% of cases are familial
autosomal dominant is most common
can also be autosomal recessive, X-linked, matrilinear
linked to 25 different chromosomal loci & genes
cause of glycogen cardiomyopathy
defects in genes of metabolism associated w/lysosome
cellular glycogen deposition observed
presentation of glycogen cardiomyopathy
hypotonia (decreased muscle tone)
electrophysiological dysfunction (caused by myocyte & myofiber disarray)
myocyte hypertrophy
cardiac fibrosis
mutations associated with glycogen cardiomyopathy
- 1,4-glucosidase→ Pompe dz
- lysosomal acid
- recessively inherited
- lysosome-associated membrane protein→ Danon dz
- X-linked
- enzyme deficiency
- galactosidase A→ Fabry dz
- X-linked
- lysosomal hydrolase deficiency
presentation of restrictive cardiomyopathy (RCM)
normal or decreased volume of BOTH ventricles
bi-atrial enlargement
impaired ventricular filling w/restrictive physiology
normal wall thickness
genetic cause of restrictive cardiomyopathy
mutation of cardiac troponin I
familial & unrelated mutation
dz process of arrhythmogenic right ventricular cardiomyopathy
progressive loss of myocytes
replaced by fatty or fibrofatty tissue
progresses from epicardium to endocardium
mostly in right ventricle, but can be seen in left ventricle
cause of arrhythmogenic right ventricular cardiomyopathy
dz of desmosome
5 different desmosomal component mutations
channelopathy
abnormality in ion channel function
cardiac channelopathies
mutations of specific ion channel proteins
What are the major cardiac channelopathies?
- long QT syndromes
- short QT syndrome
- Brugada syndrome
- conduction dz
- sinus node dysfunction
- catecholaminergic polymorphic ventricular tachycardia (CPVT)
what channel(s) are most important for repolarization?
K+ channels
what channel(s) are most important for depolarization?
Ca2+ & Na+ channels
clinical presentation of Long QT syndromes
frequently in childhood
syncopal episodes
potentially lethal torsades de pointes tachyarrhythmias
genetics of Long QT syndromes
autosomal recessive form associated w/deafness
8 gene mutations encoding ion channel subunites associated w/syndrome
what effects are seen when K+ channel subunits are mutated?
loss of function
net reduction in outward repolarizing K+ current
prolongs action potential repolarization time
long QT
what effect are seen when Na+ pore channel protein is mutated?
gain of function
increased inward Na+ current during action potential plateau
shifting balance to prolonged repolarization (longer to travel)
physiological cause of Short QT syndrome
repolarization is hastened by enhanced outward current during repolarization
K+ leaving cell faster than normal
clinical presentation of Short QT syndrome
very rare (30-40 recorded patients)
high rate of sudden death
exceptionally short QT interval= 300ms