Supraventricular Tachycardia Flashcards
Supraventricular tachycardia (SVT)
definition
tachycardia >100 whos pacemaker orignates above the ventricles.
- note that some SVts need to use the ventricles as part of their circuit though.
2 initial ways to look at ECG when diagnosing tachyarrhthmias
- regular vs irregular
- narrow QRS cs wide QRS (>120ms)
what type of QRS distribution is more likely to indicate a superventricular tachycardia
a narrow- QRS complex.
Outline the different types of re-entrant circuits which are causing theSV
- AV nodal reentry tachycardia. The AV node fires and it backs up into the atria
- AV reentry /reciprocting tachycardia– after the current goes through the ventricle, it goes back up to AV ndoe
- Atrial flutter and some atrial tachycardias. Usually atrial flutter still has a regular pattern.
outline the two focal tachycardia pacemakers
- some atrial tachycardias; certains cells in the atria can fire faster than the sinus node– takes over atria and thus ventricular rhythm.
- junctional tachycardia (AV node)
for SVT with regular narrow QRS complexes, whats the most common type of tachycadia pacemaker?
AV NODAL reentry tachycardia is most common. (AVNRT)
triggers for regular narrow QRS-complex SVT:
- stimulants
- alcohol
- anxiety/ stress/ high catecholamine states
- bending.
- exercise.
symptoms of SVT
palpitation, dizziness/presyncope/syncope
- breathlessness, fatiguw
- chest pressure/pain
- flushing, sweating.
- Diuresis (ANP-mediated).
is SVT inherently regular or irregular
SVT is a tachycardia that is a REGULAR rhythm. usually narrow QRS complexes and usually sudden onset and sudden termination.
ECG features of SVT
SVT is a tachycardia that is a REGULAR rhythm. usually narrow QRS complexes and usually sudden onset and sudden termination.
AV node reentry tachycardia (AVNRT) is started by having a proloned T wabve which causes a ___ P wave and triggers tachycardia.
What ECG findings would characterize AVNRT?
causes a retrograde P wave.
Retrograde P-waves in leads I, II, V1-V3 (anterior and superior), whcih is kinda were the AV node is.
Wolff Parkinson White syndome is characterized by a ___ SVT
AVRT (av reentry tachycardia due to an accessory pathway– but not a nodal originating like AVNRT)
ECG requirements for diagnosis of WPW syndrome (an accessory pathway AVRT SVT)
- PR interval <120ms
- normal P wave vector (SA node) (to exclude junctional rhythm: junctional rhythm occurs when the electrical activation of the heart originates near or within the atrioventricular node, rather than from the sinoatrial node. Because the normal ventricular conduction system (His-Purkinje) is used, the QRS complex is frequently narrow.)
- presence of delta wave– little fluttering on the QRS complex
- QRS duration>100ms.
delta wave
little fluttering on the QRS complex. helps to diagnose WPW. it is caused by activation of the accessory pathway in WPW syndrome before the main AC pathway gets stimulated enough, and causes a generalized tachycardia.
Look at antidromic vs orthodromic tachycardia
In orthodromic AVRT the re-entry impulse circulates in antegrade direction through the atrioventricular node.
In antidromic AVRT the impulse travels in retrograde direction through the atrioventricular node.
SVT (AVRT) in WPW can be initiated by a closely coupled premature ___ complex (PAC) which conducts initially though the AV node but then has a ___ conduction via the accesory pathway, resulting in ___ P waves produced by ___ conduction on ___ ECG leads.
SVT (AVRT) in WPW can be initiated by a closely coupled premature atrial complex (PAC) which conducts initially though the AV node but then has a retrograde conduction via the accesory pathway, resulting in inverted P waves produced by retrograde conduction on inferior ECG leads.
delta wave (seen in WPW)
Even though this person isn’t tachycardic right now, what underlying arrthmia might they have?
WPW. Caracteristic delta waves.
Overt vs Concealed accessory pathway in WPW
in overt, you can evidently see the accessory pathway because of the delta wave it creates.
In concealed, the accesory conduction doesn’t go through the atria and venricle all the time. results in absent delta wave/skinny QRS.
What kind of tachycardia is going on? What can be done to prove that this part of the heart is malfunctioning?
the regular narrow QRS complexes all have P waves before it, it’s an atrial tachycardia. If it was an escape rhythm, it might cause a funny looking P wave:
- we can test our theory that it’s atrial tachycardia by giving adenosine. Adenosine produces AV block and tachycardia should stop, since the signal can’t get from the malfunctioning atria to the ventrical, indicating that it’s an atrial driven SVT.
how does adenosine effect an SVT
it blocks the AV node. the signal cannot get to the tachycardia. atrial flutter could be exposed if there is still extra-excitation if AV node is inhibited– would indicate another location is cauing the tachycardia.
complications of ablation for SVT
vascular damage
heart block requiring permanent pacemaker
perforation/tamponade (due to catheter)
thromboembolic complications (give iV heparin)
AVNRT can be cured
permanently with catheter
ablation, using radio
frequency to heat and
destroy the cells in the
slow (accessory) pathway, creating a
permanent line of block.
Radio frequency ablation of
the accessory pathway is
often indicated in patients
with WPW who are at risk
of sudden death due to
atrial fibrillation with a
rapid ventricular response
via the bypass tract.
