Cardiac Arrythmias Flashcards
Who’s consent do you require to do a hospital autopsy?
next of kin or family
What are the circumstances that a procurator fiscal would instruct an autopsy?
sudden and unexplained death suspected suicide or homocide death of a child death at work death due to medical or dental care death in custody death due to an industrial or notifiable disease death due to an accident
What are the two broad catagories of inherited cardiac arrythmias?
cardiomyopaties
channelopathies
What causes channelopathies?
ion imbalance and development of early and late depolarisations
Give some examples of a channelopathy?
long QT syndrome brugada syndrome catecholaminergic polymorphic ventricular tachycardia (CPVT) short QT syndrome familial AF WPW progressive familial conduction disease
What causes cardiomyopathies?
scar or electrical barrier formation causing re entry
What are examples of cardiomyopathies?
hypertrophic cardiomyopathy
arrythmogenic right ventricular cardiomyopathy (ARVC)
dilated cardiomyopathy
What is an after depolarisation?
abnormal depolarisation of cardiac myocytes that interrups phase 2,3 or 4 of the cardiac AP
What are early after depolarisations?
abnormal depolarisation in phase 2 or 3
caused by increased frequency of abortive action potentials before normal repolarisation is completed
What can early after depolarisations result in?
torsades de pointes
What can make early after depolarisations worse?
hypokalaemia
drugs that prolong the QT interval
What are delayed after depolarisations?
begin during phase 4 - after repolarisation is complete but before another action potential would normally occur
What causes delayed after depolarisations?
elevated Ca
seen in digoxin toxicity
overload of the SR can cause spontaneous Ca release
What is the classical feature of delayed after depolarisations?
bidirectional ventricular tachycardia
In what condition do delayed after depolarisations occur?
CPVT
What is the incidence of congenital long QT syndrome?
1 in 2000 are carriers
What is long QT syndrome?
polymorphic VT (i.e. torsades de pointes) due to adrenergic stimulation
What are the autosomal dominant varieties of long QT?
isolated: Romano Ward Syndrome
extra cardiac features: Anderson-Twail syndrome, Timothy syndrome
What are the autosomal recessive varieties of long QT?
associated with deafness: Jervell + Lange-Nielsen Syndrome
What causes long QT syndrome?
genetic mutations that cause reduced or dysfunctional ionic current - causing prolonged cardiac repolarisation
more depolarising current - Na and Ca
less repolarising current - K
How is LQTS diagnosed?
QTc>/= 480ms
What factors contribute to sudden death in LQTS?
age dependant
gender - pre adolescent males and adult females
increasing QT duration
prior syncope and response to beta blockers
How is LQTS managed?
lifestyle - avoid stress, strenuous exercise, loud noise if recessive, strenuous swimming if dominant
beta blockers
ICD
avoid QT prolonging drugs
What drugs are QT prolonging?
antipsychotics - haloperidol antibiotics - macrolides (erythromycin) anti arrythmics - class 1a and 3 anti emetics - ondesantron anti depressants - tricyclics
What causes congenital short QT syndrome?
mutation in the K channels
How is congenital short QT syndrome diagnosed?
QT <300ms at a HR of <80bpm
How does congenital short QT present?
often in young children
associated with AF
What is Brugada syndrome?
VT and VF due to triggers for eg - sleep, fever, alcohol, large meals
What causes Brugada syndrome?
genetic mutations for eg SCN5A and CAN1AC
How is Brugada syndrome inherited?
autosomal dominant
Who is at higher risk of Brugada syndrome?
females x 8
How does Brugada syndrome look on ECG?
ST elevation >2cm in V1 +/- V2
RBBB in V1-V3
How can you elict Brugada syndrome?
flecainide
How does flecainide stimulate Brugada syndrome?
blocks the cardiac Na channel
How do you treat/manage Brugada syndrome?
avoid drugs that induce ST elevation
avoid excessive alcohol or large meals
ICD for those with previous cardiac arrest or type 1 ECG pattern or history of syncope
What drugs induce ST elevation?
anti arrythmics
psychotropics
analgesics
anaesthetics
What is Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)?
adrenergic induced bidirectional and polymorphic VT, SVT triggered by emotional stress and activity
How does CPVT appear on ECG and ECHO?
normal
How is CPVT inherited?
autosomal dominant or recessive
How can CPVT be managed?
lifestyle - avoid emotional and physical stress
beta blockers
ICD - if contraindicated give flecanide
How does Wolff-Parkinson-White syndrome present?
AVRT and AF
small risk of sudden death
How does Wolff-Parkinson-White look on ECG?
delta wave and short PR interval due to ventricular pre excitation due to the accessory pathway
How is hypertrophic cardiomyopathy inherited?
autosomal dominant
What gene is mutated in hypertrophic cardiomyopathy?
sarcomere gene
How does hypertrophic cardiomyopathy present?
AF
heart failure
sudden death
How is hypertrophic cardiomyopathy treated?
lifestyle - avoid emotional and physical stress
ICD if prior cardiac arrest/sustained VT or if LV wall thickness >/= 30mm
What genes are affected in dilated cardiomyopathy?
lamnin A/C and desmin
dystrophin if X linked
Who is more affected by dilated cardiomyopathy - males or females?
males
What is Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)?
fibrofatty replacements of cardiomyocytes
LV involvement in >50% of cases
How is ARVC passed on?
autosomal dominant - genes for desmosomal proteins
autosomal recessive - genes for non desmosomal proteins
What does ARVC cause?
a reentry VT
How is ARVC managed?
avoid competitive sport
beta blockers
ICD
