Arrythmia Flashcards
what is arrhythmia
problem with heart rate
what is bradycardia
slowed heart rate
what is tachycardia
increased heart rate
how can we classify arrhythmia
Location of damage
Effect on rate
describe the structure of the heart
Structure of the heart
- left and right atria
- left and right ventricle
Atria and ventricles split by bicuspid and tricuspid valves
Seperated via septum
describe the conduction of a heart beat
Sino atrial node conducts an action potential down to the atrio ventricular node
where there is a sleight delay 0.1s to allow the atria to contract.
This then goes down the bundle of his into the atrioventricular bundle branches down into the perkinje fibers causing the ventricle to contract in unison.
What are the 5 phases of a cardiac action potential
0 rapid depolarization
1 initial repolarization
2 plateux
3 repolarization
4 baseline
What does Na+ influx lead to
rapid depolarization (phase 0)
what does Ca2+ influx lead to
slow depolarization (phase 2)
what does K+ efflux lead to
repolarization and hyperpolarization (phase 3)
what is refractory period of the heart
time take to evoke another Ap constriction limiting absolute contract rate
what is refractory period dependent on
Na+ channels
describe how action potentials in pacemaker cells work
action potential threshold higher than in muscles -65 needed
slower upstroke of AP gives slower conduction due to L type voltage dependent calcium channels
resting membrane potential is unstable called the pacemaker potential
what is the rhythm of the heart controlled by
autonomic nervous system (ANS)
describe how the ANS acts on the heart to controll heart rate
right vagus has acetyl choling acting on M2 receptors
symptathetic noradrenaline acts on beta 1 adrenoceptors
left vagus has acetyl choline acting on m2 receptors
describe the different parts of an electrocardiogram
P wave = atrial depolarization
QRS complex = ventricular muscle depolarization
T wave = ventricular repolarization during intraventricular conduction time
PR interval = conduction from atrium to ventricle
QT interval = duration of ventricular action potential
what is heart block
damage to the conducting system of heart in total heart block, atria and ventricles beat indepndently the rate is determined by the pacemaker that is distal to the condition block.
how do we treat total heartblock
pacemaker devices
what is ectopic pacemaker activity
pacemaker activity from areas other than SAN
what are the causes of ectopic pacemaker activity
sympathetic activity can promote ectopic activity
ischaemia partial depolarization
delayed after depolarization
what is re entry - arrythmias
normally action potential dies out in ventricles as surrounding tissue is still in refractory period
damage can mean APs re-excite areas that refractory period has ended, termed re entry or circus movement
ischaemic damage a common cause can cause arterial and ventricular tachycardia and fibrillation
Describe the cardiac action potential
-96 as Na+ moves in depolarization occurs
+52 K+ and Cl- out
Ca2+ in K+ out
K+ out repolarization
what is vaugn williams classification based on
electrophysiological properties of drugs
what are the 4 classes of vaugn williams
sodium channel blockers
beta blockers
amiodarone like drugs
calcium channel blockers
what do sodium channel blockers do
block voltage gated sodium channels phase 0 of the cardiac action potential
what are the 3 classes of sodium channel blockers
Class la - intermediate kinetics
Class lb - Fast kinetics block open channel during phase 0 reducing max depolarization before next beat
Class Ic - Slow kinetics steady state of block during whole cardiac cycle
what is the role of beta blockers
block action of adrenlaine/noradrenaline on heart to prevent tachyarrhytmias
how do beta blockers work
Supress actions of sympathetic nervous system, reducing depolarization in phase 4 of the pacemaker AP
what is the overall effect of a beta blocker
Slowing heart rate and force of contraction
what are the main side effects of a beta blocker
hypertension and ischaemic heart disease
what was amiordarone like originally based on
action of amiordarone however not includes other such as sotalol
what does amiordarone like do
prolong the cardiac ap increasing the refractory period inhibiting potassium channels involved in phase 3
what are the serious potential adverse effects of amiordarone
lead to pro arrhythmic effects such by prolonging Q-T interval
what do calcium channel blocker do
they slow the conduction in the sino atrial and atrio ventricular node where action potential depends on calcium entry which reduces the duration of the plateu of the action potential
what effect does the calcium channel blocker have
reduces for of heart beat
also reduce after depolarization preventing ectopic beat
what do class 1 drugs work on
phase - 0
what do class 2 drugs work on
phase 2 and 4
what do class 3 drugs work on
phase 3
what drug are not classified in vaugn williams system
many however one of which is anti arrhytmic drugs
what is adenosine used in
supraventriculartachycardia (SVT), stops SVT if other measures fail as action are short lived it is safer than verapamil
what does digoxin do
used in Atrial fibrillation as slows AV conduction by blocking Na/K atpase involved in resetting the pacemaker cell ion balances
what non pharmacological treatment options exist for arrhythmias
DC cardioversion - electronic paddles which deliver shocks performed under anaesthetic used for SVT and VT if haemodynamically unstable
implantable defibrillator
catheter ablation high power radio waves used to lesion small areas known to be causing tachyarrhythmias
electronic pacemaker
what 4 things do we consider when managing arrhythmia
eliminate cause
make diagnosis
determine baseline condition
therapy needed?
what are the two types of tachyarrhythmias
supraventricular SVT
ventricular VT
what are some symptoms of SVT
palpitations, fainting/light headedness and shortness of breath; sometimes causes peripheral and even pulmonary oedema
what is the most common sustained arrhythmia
supraventricular artial fibrillation
what are the causes of supraventricular atrial fibrillation
hypertension valvular heart disease coronary disease heart failure hyperthyroidism pulmonary embolism lungcancer
what is the difference between a normal ecg and one with Atrial fibrilation
lack of P wave
what are the 3 types of atrial fibrillation
paroxysmal afib
persistent afib
permanent afib
Describe the nice guideline for atrial fibrillation
Confirm diagnosis
do further investigations including risk stratifcation for stroke thromboembolism
if paroxysmal af carry out rythm control if failure carry out rate control
if permanent carry out rate control and if remains symptomatic carry out rythm control
if persistant determine whether rhythm or rate then treat appropriatly
what can we use for rate control
beta blocker or calcium antagonist
sedentary patients use digoxin
what can we use for rhythm control
electrical cardioversion
pharmacological cardioversion - Class I
catheter ablation
if atrial fibrilation what is assessed
CHA2DS2Vasc
if CHA2DS2VASc score is greater than 2 in a patient with atrial fibrilation what is recommmended
anticoagulant
what is HAS-BLED used for
determine bleeding risk for use of anticoagulants in AF
if hasbled score is greater than 3 what risk is it
high risk of bleeding and thus requires additional monitoring
what is supraventricular AVNRT / AVRT termed
paroxysmal supraventricular tachycadria
what does AVNRT stand for
atrioventricular nodal re entranct tachycardia
what does AVRT
atrioventricular re entranct tachycardia
what can be used to treat supraventricular AVNRT / AVRT
often terminated by non pharmacological means e.g. carotid massage or reflex vagal stim
however can be terminated by adenosine as well
what are some causings of ventricular tachyarrhytmias
congenital heart disease
drugs that prolong long QT interval
changes in blood pH, ionic balance etc
Ischaemic heart disease
how do we treat VT and Vf
cardioversion to restore sinus rhythm
sustained VT can be treated with amiodarone class 1c or 1b
non sustained VT can be treated with a beta blocker or sotalol implantable cardioversion, catheter ablation
