Cardiac Arrhythmias Flashcards
what causes bradycardia
sinus bradycardia or conduction block
what is an arrhythmia
a disturbance in the cardiac cycle due to abnormal pacemaker activity or conduction/contraction of the heart muscle leading to an insufficient cardiac output
describe the electrical action potential seen in ventricular myocytes
influx of Na causes depolarisation
small amount fo repolarisation due to K efflux
plateau stage where there is no change in electrical charge due to equal influx of Ca and efflux of K
depolarisation due to K efflux
Na/K ATPase sets up membrane potential in refractory period
describe the action potential seen in SAN cells
funny current/pacemaker potential occurs where there is slow depolarisation due to Na influx through HCN channels
Ca influx then causes rapid depolarisation
repolarisation due to K efflux
what can cause tachycardia
ectopic activity fibrillations after depolarisations re-entry loops wolff-parkinson-white syndrome
what are ectopic beats
where points away from the SAN fire electrical impulses - these can be ventricular or supra ventricular
what can cause ectopic beats
damage to the heart e.g. in ischaemia
mitral valve disease - stenosis causes dilation of atrial and regurgitation causes irritation of atria
high blood pressure
what are after depolarisations
where there are abnormal depolarisation of the myocytes
what are early after-depolarisations
where there is abnormal depolarisation in phase 2/3 of the normal action potential
what are late after-depolarisations
where there is abnormal depolarisation in phase 4 of the normal action potential
what can after-depolarisations result in
long QT (Torsades de point) scarring of the tissue
what are re-entry loops
where an impulse is blocked and so travels backwards and re-excites the tissue it give came from giving a new action potential in quick succession
what is wolff-parkinson-white syndrome
where there is abnormal electrical conduction in the heart and the impulse travels down the bundle of Kent giving a fast heart rate
what are fibrillations
uncoordinated and irregular heart beats in either the atria or ventricles, often resulting in tachycardia
what are the causes of fibrillations
ectopic beats
high blood pressure
mitral valve disease
what is atrial flutter
irregular heart beats from the atria which are less chaotic than those seen in AF
why must anticoagulants be given with AF
as there is increased risk of clot formation and so stroke
give 3 examples of sodium channel blockers
IA - quinidine
IB - lidocaine
IC - flecainide
what do sodium blockers do
cause depolarisation to occur more slowly helping to control the rhythm of the heart
what do beta blockers do
block sympathetic activation of SAN cells by decreasing the slope of the funny current - therefore they control the rate of impulse generation
give some examples of beta blockers
propanolol and bisoprolol
what do potassium blockers do
control the rhythm of the heart by increasing the refractory period
give 2 examples of potassium blockers
amiodarone and sotalol
what do calcium blockers do
slow down the heart rate - therefore are rate controlling
what are the rate controlling drugs
calcium and beta blockers
what are the rhythm controlling drugs
Na and K blockers
give an example of a Ca blocker
verapamil
what is used to treat AF
- rate controlling drugs with digoxin
2. Rhythm controlling drugs.
what are beta blockers used for
rate control in AF
tachycardia
what are calcium blockers used for
rate control in AF
tachycardia
what is amiodarone used for
any arrthymia
what are the side effects of amiodarone
pulmonary fibrosis, hepatic damage, thyroid disease and increased LDL
what is sotalol used for
tachycardia
rhythm control in AF
what are the side effects of sotalol
increased QT (Torsades de Points)
what is adenosine used for
diagnosis for coronary artery disease
supra-ventrciular tachycardia
what does adenosine do
stops the heart for 20 seconds
what is digoxin used for
AF
how does digoxin work
inhibits Na/K/ATPase so slows down the heart rate
what is used to treat Wolff-parkinson-white syndrome
flecainide
what is lidocaine used to treat
tachycardia due to ischaemic heart disease
can flecanide be used on its own
no - will increase the hearts response to supra-ventriulcar arrhythmias causing an increase in heart rate - so needs to be used with AVN blocker
