Supraventricular Tachycardia Flashcards
different types of SVT arise from or are propagated by the _____ or __ ____, typically producing a ______ complex tachycardia (unless aberrant conduction is present)
different types of SVT arise from or are propagated by the atria or AV node, typically producing a narrow complex tachycardia (unless aberrant conduction is present)
name some regular atrial tachycardias?
- sinus tachycardia
- atrial tachycardia
- atrial flutter
inappropriate sinus tachycardia - sinus node re-entrant tachycardia
name some irregular atrial tachycardias?
- atrial fibrillation
- atrial flutter with variable block
- multifocal atrial tachycardia
name some regular av tachycardias?
- atrioventricular re-entry tachycardia
- AV nodal re-entry tachycardia
- automatic junctional tachycardia
what 2 arrhythmias are commonly referred to as paroxysmal SVTs?
AV nodal re-entrant tachycardia and AV re-entrant tachycardia
who normally gets paroxysmal SVT?
often seen in young people with no or little structural heart disease
what category of arrhythmia does WPW fit into?
accessory pathway tachycardia - AVRT
what is the difference between sinus tachycardia and SVT?
with SVT, impulses in the atria fire rapidly and cause interference with the SA node. But in sinus tachycardia, the heart is functioning normally; only the SA node is firing at a higher than normal rate.
In AVRT there is a large circuit comprising the AV node, the His bundle, the ventricle and an abnormal connection from the _____ back to the ______.
In AVRT there is a large circuit comprising the AV node, the His bundle, the ventricle and an abnormal connection from the ventricle back to the atrium.
what causes an accessory pathway
result from incomplete separation of the atria and the ventricles during fetal development.
Clinically, the AVNRT often strikes suddenly without obvious ______, but ____, _____, ___ and _____ may aggravate or induce the arrhythmia.
Clinically, the tachycardia often strikes suddenly without obvious prov- ocation, but exertion, coffee, tea and alcohol may aggravate or induce the arrhythmia.
what are the ECG features of AVNRT?
no visible P waves
narrow QRS
what are the ECG features of AVRT?
P waves visible between QRS and T wave
what are the ECG features of Atrial tachycardia?
organised atrial activity with P wave morphology different from sinus rhythm preceding QRS
why does atrial tachycardia usually occur?
because of congenital heart disease, iatrogenic causes or atrial ischaemia
how is acute SVT managed?
vagal manoeuvres
IV adenosine
IV verapamil
which receptors does adenosine work on?
it activates A1 adenosine receptors coupled to Gi/o
what does the adenosine binding to the receptor do?
opens ACh sensitive K channels (GIRK)
this hyperpolarises the AV node briefly, suppressing impulse conduction
adenosine has a very ____ acting time?
short
what does verapamil block?
it blocks L-type Ca channels
what is the effect of blocking Ca channels?
slows conduction and prolongs refractory period in AV node and bundle of his
verapamil is also a ____
vasodilator
when would you not use verpamil
if someone has an already low BP
how do you manage chronic SVT?
radio frequency ablation
maybe antiarrhythmics
which classes of antiarrhythmics would be used in chronic SVT?
II and IV
what is radiofrequency ablation?
this is the selective cautery of cardiac tissue to prevent tachycardia, targeting either an automatic focus or part of a re-entry circuit
before radiofrequency ablation what medications should be stopped and how long before hand?
cease antiarrhythmic drugs 3-5 days before
what kind of anaesthesia is used in the ablation procedure?
local
how long is ablation usually?
1-2 hours
ABLATION
- catheters placed in heart via ______ veins
- intracardiac ECG recorded during ______, _____cardia and during _____ manoeuvres
- catheter placed over _____/_____ and tip heated to __ - ____C
- catheters placed in heart via femoral veins
- intracardiac ECG recorded during sinus rhythm, tachycardia and during pacing manoeuvres
- catheter placed over focus / pathway and tip heated to 55-65C
