Arrhythmias Flashcards
(96 cards)
what is a cardiac arrhythmias?
disturbances to heart rate, or rhythm
what 2 things may cause arrhythmias?
Changees in;
1) impulse formation
2) impulse conduction
how are arrhythmias described? (2)
1) rate
- bradycardia
- tachycardia
2) site of origin
- supra-ventricular (atria & AV node)
- ventricular
alterations in impulse formation can involve what 2 things?
1) changes in auto-maticity
2) triggered activity
abnormalities in impulse conduction arise from what 3 things?
1) re-entry
2) conduction block
3) accessory tracts
what components of the cardiac conduction system demonstrate a spontaneous phase 4 depolarisation & automaticity?
all components of cardiac conduction
what is the fastest pacemaker in the heart?
SA node (usually 70-80BP M)
what is SA nodes pacemaker ability to be dominate over other ‘latent’ pacemakers known as?
Overdrive suppression
what does the SA node need to discharge in order to exert normal control of rate & rhythm?
= must discharge action potentials at higher, regular frequency than any other structures in the heart
what 2 things may altered automaticity be?
1) physiological
2) patho-physiological
what does pathophysiology mean in the setting of altered automaticity?
when the function of the SA node, as the normal pacemaker, is taken over by another ‘latent pacemaker’ as the result of overdrive suppression
when might SA node lose its overdrive suppression occurs? (2)
1) if SA node firing frequency is pathologically low
2) if conduction of impulse from SA node is impaired
what is an escape beast?
a impulse that is generated by a latent pacemaker
what is an escape rhythm?
= series of ectopic beats
- a run of impulses generated by latent pacemakers
when else might the SA node lose its overdrive suppression?
- if the latent pacemaker fires at an intrinsic rate faster than the SA node rate (even if SA node is functioning normally)
what sort of beats do latent pacemakers initiate?
what do the beasts generate?
= an ECTOPIC BEAT
= ECTOPIC RHYTHM
- ectopic meaning abnormal place or position
when may ectopic rhythms result?
1) ischaemia
2) hypokalaemia
3) increased sympathetic activity
4) fibre stretch
5) others
when else might the SA node lose its overdrive suppression?
in response to tissue damage
- i.e. post myocardial infarction
Yes or No.
can non-pacemaker cells, when partially depolarised, assume spontaneous activity?
Yes
what is after-depolarisations (AD)?
when a normal action potential triggers ABNORMAL oscillations in membrane potentials that occur during or after re-polarisation
If the ADs is of a sufficient amplitude to reach threshold what would it cause?
premature action potentials & beats
what 2 things can after-depolariisation be?
1) early after-depolarisation (EADs)
2) delayed after-depolarisation (DADs)
what might a repeated after-depolarisation cause?
sustained arrhythmia
when would the EADS occur?
during the inciting action potential within;
1) phase 2 - AD mediated Ca2+ channels
2) phase 3 - AD mediated by Na+ channels