sudden death Flashcards
what is sudden death
natural, rapid, unexpected
not trauma, toxicity, poison or chronic illness
causes of sudden death
heart +/- vessels
non cardiac vessels (eg stroke or aneurysm)
pulmonary system (PE)
CNS (rare seizures in epilepsy)
what is sudden cardiac death
sudden death due to cardiovascular/coronary vessels
most due to arrhythmias
what are the direct causes of sudden cardiac death
coronary obstruction
infarct
embolism
arrhythmia/dysrhythmia
what disorders lead to risks for sudden cardiac death
CHD/ low LVEF
structural heart disease-also dev/genetic structural pathologies
primary arrhythmia
what is a cardiac arrest
a sudden stop in effective blood circulation due to failure of the heart to contract effectively or at all
is a cardiac arrest the same as a MI or HF
No
Can result from AMI (blood flow to heart muscle impaired)
AMI - heart cont pumping but less effectively
HF - circulation substandard, still pumping and sustaining life
what is arrhythmia and dysrhythmia
same thing - a variation in the normal beating pattern or rhythm of the heart
usually due to disorganisation of electrical signals running through the heart
can be fast, slow, abnormal
what are the electrical causes of arrhythmia
primary or arrhythmogenic.
ion channels and electrical issues at cellular level
extra conduction pathways at the organ level
what are the structural causes of arrhythmia
unusual shape or size of cardiac tissue so changes signal pathway, can lead to delays that interfere with conduction cycle
what are the ischaemic causes of arrhythmia
hypoxia makes heart tissue electrically unstable
effectively changes signal pathway, leading to delays interfering with conduction cycle
what are the causes of primary arrhythmia
unstable myocardium (damage, hypoxia eg AF) Ion channels (channelopathies, long QT syndrome) Accessory conduction pathways
what is cardiomyopathy
heart size, shape or thickness is (structure and function) abnormal (not CAD, hypertension, heart valves and HD present at birth)
what are the consequences of cardiomyopathy
risk of pumping dysfunction or low output HF
conduction abnormalities
what are the types of cardiomyopathy
dilated (eccentric)
hypertrophic (concentric)
what developmental defect is associated with a higher risk of sudden death
tetralogy of fallot
associated with higher risk even after childhood surgery
what do you need to have for an arrhythmia
trigger and substrate
what is a trigger
brief event required to initiate a period of arrhythmia
precipitating event
eg extrasystole or atrial flutter (extra firing)
what is a substrate
ongoing, underlying tissue instability that increases triggers or allows for maintenance/amplifications of dysrhythmias
what can substrates be
predisposing factor
electrical (eg genetic or pharmacological issues with ion channels or electrolytes) or structural defect (eg fibrosis or inflammation caused by IHD)
what is a R on T (ECG phenomenon)
type of potential trigger for arrhythmias
on ECG - premature QRS on previous T wave
T wave is a vulnerable period (repolarisation of ventricular AP, refractory period ending)
Resulting QRS= premature ventricular contraction
what is a pacemaker
implanted electronic device - electrodes to stimulate heart
consistently applies impulses for each heart beat
mostly used for bradyarrhythmias and heart block
what is an Implantable Cardioverter Defibrillator (ICD)
same as pacemaker but only applies electrical impulses when V arrhythmias detected to protect from fast or uncontrolled rhythms
what are indications for implanting an ICD
cardiac arrest due to ventricular fibrillation
symptomatic HF with low LVEF (LOHF after MI)
cardiomyopathies - eg dilated
congenital
channelopathies
what are antiarrhythmic drugs
usually affect ion channel activity or sympathetic drive
eg amiodarone, beta blockers, digoxin for AF
mostly for supraventricular arrhythmias (atria or AV node)
what is reperfusion injury
tissue damage caused when blood supply returns to the tissue after a period of ischaemia or hypoxia
can lead to electrical irregularities & risk
what causes reperfusion injury
the restoration of circulation results in inflammation and oxidative damage
what are preventative treatments for reperfusion injury
cooling
immunosuppression
oxygen radical scavengers
how can syncope be distinguished from seizure
both loss of consciousness
may have no symptoms when not occurring
Syncope registered by Holter monitor (24 hr ECG)
Seizure registered by EEG (brain imaging is also important)
seizures associated with stiffness/unusual posture
seizures tip and syncope crumple
convulsive syncope can feature both
what is vasovagal syncope
Vagal increase (& symp decrease) - vasodilatation and low heart rate Triggered centrally (ie brain) not at level of heart most common form of syncope, common in young adults and is recurrent
what is exertion syncope
Neurocardiogenic origin
Benign
what is index case
the initial patient in the population of an epidemiological investigation
what is the proband
In medical genetics, the index case is the case of the original patient that stimulates investigation of other members of the family
what is the number needed to treat
Statistical measurement of the impact of a medicine or therapy
Averagenumber of patients who need to be treated to prevent one additional bad outcome
can arrhythmia be detected
genetic screening
what is penetrance
proportion of individuals carrying a particular variant (or allele) of a gene that also expresses an associated trait (the phenotype)
what is incomplete or reduced penetrance
do not express trait even though they carry the allele
channelopathies can vary from patient to patient
phenotypes of disease can differ
most diseases are polygenic
what is the epidemiology of sudden cardiac death
50% all cardiac death
more male
peak 45-75y/o
majority related to coronary disease
what are the mechanisms of arrhythmias
substrate (structure or elec) ectopic activity (early after depolarisation, short coupling interval, delayed after depolarisation) re-entry wave break
what is re-entry
reconduction through an area of unidirectional conduction block
circuit larger, refractory period abnormal, zone of slow conduction - allow for repolarisation
how can IHD contribute to arrhythmias
acute ischaemia
ventricular remodelling - scar formation, myocardial fibrous, coupling, dilatation, poor function
how does an infarction affect the heart
zone of infarction to injury to ischaemia which spreads
what can cause dilated cardiomyopathy
idiopathic viral alcohol drugs autoimmune
what is the pathophysiology of dilated cardiomyopathy
myocardial fibrosis neurohumoral activation increased sympathetic tone electrolyte disturbances = ectopy, re-entry, VT/VF
what is hypertrophic cardiomyopathy
most common cause of SCD in young athletes
autosomal dominant, incomplete penetrance
mutation of cardiac muscle sarcomere genes
commonly beta-myosin or troponin-T
LV outflow obstruction, anterior motion of mitral valve, asymmetrical septal hypertrophy
what are symptoms of hypertrophic cardiomyopathy
asymptomatic exertion chest pain/dyspnoea exertion syncope palpitations mechanism of SCD unclear
what is arrhythmogenic RV cardiomyopathy
30-50% familial
multi-genomic
replace RV myocardium with fibro-fatty tissue
RV hypertrophy and dilation
VT/VF due to re-entry around interstitial fibrosis
what are the symptoms of ARVC
asymptomatic
exertional syncope
atrial arrhythmias common
epsilon wave on ECG
what are other structural causes of SCD
aortic stenosis
mitral stenosis
mitral valve prolapse
congenital heart disease (anomalous coronary arteries, Epstein’s anomaly, complex like tetralogy)
what are primary arrhythmias
non ischaemic
structurally normal heart
syndromes include - long QT, WPW, Brugada, primary VT/VF
what is WPW
Wolff-Parkinson-White accessory pathway from atria to ventricle atrial arrhythmia ventricular pre-excitation VTVF clues on resting ECG
what is Brugada
channelopathy mostly SCN5A - fast-type sodium channel reduce conduction velocities particularly affects RVOT prone to VT arising from RVOT
How can SCD be treated
identify those at risk
preventative treatment - underlying cause, avoid precipitants, anti-arrhythmic meds, ICDs
family screening if appropriate
what are the types of ICDs
S-ICD - subcutaneous, on breastbone
Transverse ICD - intravascular, tip of lead in contact with right V
how are patients selected for an ICD
Cardiac arrest survivors VT with haemodynamic compromise high risk - CAD, poor LV function, broad QRS Some HCM, long QT, Brugada, ARVC Congenital HD
What are ICD indications for HCM
survived cardiac arrest one or more of VF/spontaneous sustained VT Unexplained syncope LV wall thickness over 30mm spontaneous NSVT abnormal exercise BP family history of premature sudden death
