Arrhythmias Flashcards
What HR is considered bradycardia?
<60 bpm (<50 bpm when asleep)
What are arrhythmias?
Arrhythmias are common disturbances of cardiac rhythm which are:
*Often benign, but may reflect underlying heart disease
*Often intermittent, causing diagnostic difficulty
*Occasionally severe, causing cardiac compromise
What HR is considered tachycardia?
> 100 bpm
What are the two broad groups of tachycardia?
1) supraventricular tachycardia
2) ventricular tachycardia
What structure acts as the pacemaker of the heart?
SAN
What branch of the nervous system acts to slow the activity of the SAN?
parasympathetic nervous system
Give an example of a hormone that can accelerate automacy of cardiac depolarisation:
adrenaline from sympathetic stimulation can produce sinus tachycardia
What constitutes ‘supraventricular’ rhythms?
- Sinus rhythm
- Atrial rhythm
- Junctional rhythm
Describe how abnormal oscillations can come about in cardiac tissue:
myocardial damage can result on oscillations at the end of the action potential called ‘after depolarisation’
Give 4 factors that may exaggerate abnormal oscillations of the heart:
1) catecholamines
2) electrolyte disturbances
3) hypoxia
4) acidosis
What is cardiac re-entry?
when a ring of cardiac tissue surrounds an unexcitable core (e.g. region of scarred myocardium) resulting in electric signals not completing the normal circuit, but rather an alternative circuit looping back upon itself
Give 2 intrinsic causes of bradycardia:
1) acute ischaemia and infarction of the SAN
2) chronic degenerative changes such as fibrosis of the atrium and SAN
Give 5 extrinsic causes of bradycardia:
1) hypothermia
2) hypothyroidism
3) raised intracranial pressure
4) beta blockers
5) antiarrhythmic drugs like digoxin
What is sick sinus syndrome?
Physiologically inappropriate sinus bradycardia, sinus pause, sinus arrest, or episodes of alternating sinus tachycardia and sinus bradycardia
What usually causes sick sinus syndrome?
idiopathic fibrosis
What are the two broad management approaches for sinus bradycardia?
1) remove any extrinsic factors (e.g. hypothermia, beta blockers)
2) pacemaker
What is heart block?
a conduction abnormality in either the AV node of conducting tissue of the heart
Where is the block found in atrioventricular block?
AV node or bundle of His
Where is the block found in bundle branch block?
lower conducting system (e.g. Purkinje fibres)
What is first degree atrioventricular block?
prolonging of the PR interval to more than 0.2 seconds followed by conduction of the ventricles for each P wave
What is second-degree atrioventricular block?
Where P waves conduct and others do not
What are the three types of second-degree atrioventricular block?
1) Mobitz I block
2) Mobitz II block
3) 2:1 or 3:1 (advanced) block)
Is AF narrow complex or broad complex?
Narrow
What are class I antiarrhythmic drugs?
membrane depressant drugs that reduce the entry of Na+ into the cell which slows conduction or reduces spontaneous activity
How do Class Ia antiarrhythmic drugs work?
they lengthen the action potential
Give an example of a Class I antiarrhythmic drug:
disopyramide
Give two examples of Class Ib antiarrhythmic drugs:
1) lidocaine
2) mexiletine
How do Class Ib antiarrhythmic drugs work?
they shorten the action potential
Give an example of a Ic antiarrythmic durg:
flecainide
What are class II antiarrhythmic drugs?
drugs and affect and prevent the effects of catecholamines of the action potential (beta-adrenoceptors)
Give an example of a class II antiarrhtymic drug:
bisprolol (beta blockers)
What are class III antiarrytmic drugs?
drugs that prolong the action potential by blocking the K+ current
Give two examples of class III antiarrythmic drugs?
1) amiodarone
2) sotalol
What are class IV antiarrythmic drugs?
non dihydropyridine calcium-channel blockers that act to slow conduction of nodal tissue
Give two examples of class IV antiarrythmic drugs:
1) diltiazem
2) verapamil
