Cardiac arrythmias epidemiology and Aetiology Flashcards
arrythmia other name
dysrhythmia
arrythmia
abnormality of electrical rhythm
types of arrythmia (2)
benign and malignant
arryhmia symptoms
palpitations
palpitation causes (3)
critical reduction in cardiac output, altered AP generation or altered AP conduction processes
ECG
electrocardiogram
AP
action potential
ECG mV
1-2
AP mV
100
baseline in ECG
isoelectric line
ECG P
atria depolarisation
ECG P to Q
AV node delay
AV
atrioventricular node
ECG QRS duration
ventricle depolarisation
what happens just before P in an ECG
SA node fires
SA
sinoatrial node
ECG T
ventricle repolarisation
ECG QT interval
ventricular AP
SA node firing to Q
atrial AP
prevelance of arrythmia
high
what are arrythmias normally
asymptomatic without provocation
arrythmia prevalence in >60 y/o
5-9%
highest mortality of MI caused by
arrythmia
getting an arrythmia (2)
acquired or genetic
bradyarrythmia
too slow
tachyarrythmia
too fast
fibrillation
irregular or unsynchronised electrical activity and
arrythmia origin (2)
atrial and ventricular
AF
atrial fibrillation
normal rhythm
sinus rhythm
AF ECG features (3)
irregular QRS complexes and no P wave, rough T wave
AF prevalence
2-4%
AF risk factors (2)
obesity and age
AF prevalence att 80 y/o
20%, growing health problem
VF
ventricular fibrillation
VF ECG features (2)
no QRS complex, squiggly line
when is VF most common
post MI or stroke
MI
myocardial infarction or thrombosis
does VF need an MI
not always
Types of AF (3)
paroxysmal, persistent, permenant
paroxysmal
bursts
persistent
regular
permanent
constant
what makes AF difficult to detect
asymptomatic
how is AF normally detected
investigating other cardiac abnormalities
how can AF lead to heart failure
tachycardia
other causes of VF (3)
hypertrophy, hypertension, myocarditis
VF results in sudden
cardiac and brain death
how is automaticiy normally altered (2)
unstable rhythm or alternative pacemaker emergence
Causes of altered AP generation
altered calcium ion homeostasis and unstable RMP
types of oscillation in altered AP generation (2)
EAD and DAD
EAD
early afterdepolarisation
DAD
delayed afterdepolarisation
when is AP triggered
once threshold is reached -40 mV
order of ionic channels in pacemaker cells generating AP
T type Ca open and If opens, some Ca open If closes, lots of L type Ca open, Ca open and K open, K closes and If opens
If
net sodium entry
Potassium channels role
repolarises
repolarisation overshoot
-60 mV
AP depolarisation mV
+15 mV
what does SA normally do to other pacemakers
overdrives
sympathetic regulation of pacemakers
adrenaline and noradrenaline
parasympathetic regulation of pacemakers
acetylcholine
sympathetic effect on pacemaker
increased If and ICa, decreased IK
parasympathetic effect on pacemaker
decreased If and ICa, increased IK
how can abnormality in automaticity occur (3)
increased sympathetic effect on latent pacemaker takes over, increased parasympathetic on pacemaker, injured node area
what happens if a node area is injured (3)
other cells develop pacemaker function, loss of RMP, osciallations
what can cause injury to a nodal area
Ischaemia
normal AP features (3)
stable RMP, coverts to pacemaker activity, ventricular longer phase 2 than atrial
AP phase 0
fast sodium channel opens
AP phase 1
fast sodium channel closes
AP phase 2
L type Ca channels open
AP phase 3 (2)
K channels open, Ca channels close
AP phase 4
stable RMP
triggered impulses
EAD and DAD
when does EAD occur
early in AP repolarisation
when is EAD more likely to occur (2)
long AP duration or long QT syndromes
what causes EAD in long repolarisation
voltage gated Ca channels are reactivated
EAD can lead to
self perpetuating tachyarrythmia
sodium channel mutations for EAD
SCN5A
SCN5A mutation effect (3)
channel doens’t stay inactivated, inward current occurs late, extends duration
potassium channel mutations for EAD (2)
KCNQ1 or HERG
KCNQ1 or HERG mutation effects (2)
decreased repolarising K efflux and plateau termination delay
when does DAD occur
after repolarisation
what conditions are prone to DAD (2)
reliance on Na Ca exchanger for relaxation or RMP depolarised