Arrythmias Flashcards
Arrhythmias are described in terms of
rate and site of origin
Rate
Bradycardias
Tachycardias
Site of origin
Supraventricular
Ventricular
alterations in impulse formation involve
Changes in automaticity
Triggered activity
abnormalities in impulse conduction arise from
Re-entry
Conduction block
Accessory tracts
Partial conduction block
Slowed conduction
Tissue conducts all impulses, but more slowly than usual
First degree block
longer PR interval
Intermittent block
Tissue conducts some impulses but not others
2 types of 2nd degree heart block
Mobitz Type 1
Mobitz Type 2
Mobitz Type 1
PR interval gradually increases from cycle to cycle until AV node fails completely and a ventricular beat is missed
Mobitz Type 2
PR interval is constant but every nth ventricular depolarisation is missing
Missing R waves
Complete heart block
No impulses conducted through affected area
Accessory pathway
Electrical pathway parallel to AV node
Bundle of Kent
Impulse through bundle of Kent is quicker than through AV node
Ventricles receive impulses from both normal and accessory pathways
Ventricular arrhythmias occur
Origin is ventricle
Supraventricular arrhythmias occur
Origin is above ventricle
(SA node, atria, AV node,
Ectopic beats
Beats originating in places other than SA node
A normal action potential may trigger abnormal oscillations in membrane potential called
afterdepolarisations
Repeated afterdepolaristaions can cause
an arrhythmia
Early afterdepolarisation
Occur when heart rate is slow
Can lead to Torsades de Pointes
Delayed afterdepolarisation
Occur when heart rate is fast
Triggered by drugs increasing Ca++ influx
1st degree heart block story
Wife (P) waits at home
Husband (QRS) comes home late every night but at the same time
2nd degree heart block Type 1 story
Wife (P) waits at home
Husband (QRS) comes home later and later every night until one day he doesn’t come home at all
2nd degree heart block Type 2 story
Wife (P) waits at home
Husband (QRS) sometimes comes home, sometimes doesn’t