SVTs Flashcards by Ashley Watercott

abnormally fast rhythm that originates above the bifurcation of bundle of His

Supraventricular tachyarrhythmias (SVTs)

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SVT originators (4)

SA node
Atria
AV node
anatomic structures

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majority of SVT caused by

reentry

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abnormally of conduction in which the same electrical impulse reenters and re-excites an area of the heart

reentry

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reentrant circuit is established around an

inexcitable obstacle

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inexcitable objects

valve, vessel opening, scar tissue

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cardiac tissue that forms the reentrant circuit

substrate

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connected proximally and distally to normal conduction tissue

two pathways

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one pathway is blocked so the reentrants dies out in one direction, but propogates in the other direction

unidirectional block

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Pathway Fast (B) blocked pathways has a ____ effective refractory period so it recovers ____

Longer

slowly

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unblocked pathway, which gives the conductive cells in the rest of the circuit time to repolarize before the reentrant wavefront arrives

slow conduction

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slow pathway has ___ ERP so it recovers ____

shorter

quicker

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area of repolarized tissue just ahead of a reentrant wavefront is

excitable gap

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reentry only occurs if there is a

premature impulse

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premature impulse can get in if

fast pathway is refractory and slow pathway has recovered

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trigger for reentry may be (4)

PAV, PVC, PJC, pacing stimilus

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premature impulse first travels through the unblocked pathway (which is the ___)

slow pathway

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EP studies reentry mechanisms (4)

mode of initation
activation sequence
tachycardia zone
antegrade/retrograde conduction patterns

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find site from which tachycardia can be most easily induced

mode of initiation

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id any conduction delay zones, reentrant pathways, or activation of normal tissue

activation sequence

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id the range of coupling intervals taht initiate reentry.

tachycardia zone

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help localize reentrant circuit and determine if the atrial or ventricular myocardium are part of the reentrant circuit

antegrade or retrograde conduction patterns

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precisely timed stiumuli are delivered into an acative reentrant circuit to create wavefronts that collide and extinguish reentrant wavefront

terminant an SVT

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synchronized to the sensed tachycardia rate but delivered at a slightly faster rate

first paced stimulus

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first paced stimulus is to create refractory in

excitable gap

originates in a microreentrant circuit enclosed within the SA node

SA nodal reentrant tachycardia (SANRT)

sinus node reentry atrial activation is

normal

originates in a microreentrant circuit in teh right or left atrium.

intraatrial reentry tachycardia

if earliest atrial signal is recorded by the HIS EGM

the origin of AT is most likely the anteroseptal RA

if earliest atrial signal is recorded by the PROXIMAL CS EGM

the origin of AT is most likely the posteroseptal RA

if earliest atrial signal is recorded by the LOW OR HIGH RA EGM

the origin of AT is most likely the somewhere in the RA

if earliest atrial signal is recorded by the DISTAL CS EGM

the origin of AT is most likely the lateral LA

if earliest atrial signal is recorded by the HRA EGM

right superior pulmonary vein

confined to macroreentrant circuit in the RA

typical atrial flutter

travels SA - pectinate muscles - right atrial floor - interatrial septum -

counterclockwise atrial flutter

confined to its conduction pathway by the crista terminalis, eustachian ridge, triscupid valve

counterclockwise atrial flutter

area of slow conduction

triscupid isthmus

counterclockwise atrial flutter signal is detected by

proximal CS or HIS catheter

counterclockwise atrial flutter signal travels in sequence down what catheter

proximal to distal HRA Catheter

P wave morphology counterclockwise atrial flutter

P waves are positive in Lead V | negative in leads II, III and AVF

P wave morphology clockwise atrial flutterECG postitive and negative (p waves)

Upright P waves in inferior leads II, III and AVF and inverted P waves in Leads V

variations of A FLutter (2)

atypical flutter | scar related atrial flutter (from Congential ehart defect)

shorter cycle length and is less stable. transition from/to AF is common. may rotate around anatomic structures

Atypical Atrial Flutter

rotates around scar tissue

scar-related atrial flutter

caused by multiple wavelet reentry or multiple automatic foci

atrial fibrillation

adjacent myocardial cells have different refractory periods

multiple wavelet reentry

AF may be caused by multiple wavelet

automatic foci

this arises from venous structures such as musclar ridges that surround the pulmonary veins

automatic foci

requires slow conduction and short refractory periods

multiple wavelet reentry

originates in dual pathways of Koch's triangle

AV nodal reentrant tachycardia (AVNRT)

AVNRT type of reentrant arrhythmia

microentrant

classic sign of AV nodal pathway is increase in AH interval

>= 50 ms | called AH jump

AV nodal reentry, premature impulse travels down what pathway

slow then up fastway

a second atrial beat that occurs at teh same time as teh ventricular beat

echo beat

earliest activation in typical AVNRT is recorded by the ___ catheter.

HIS EGM

AVNRT VA intervals are short (XX ms)

<70 ms

3 variations of AV nodal reentry

slow-fast AV nodal reentry with posterior exit fast-slow AV nodal reentry SLow-slow AVNRT

earliest signal in slow-fast AVNRT is recorded by the proximal

CS electrode

ERP of fast pathway is shorter than that of the slow pathway - so reentry occurs in teh opposite direction VA is longer AH interval is short HA interval is long

fast-slow AV nodal reentry

two slow pathways AVNRT

slow-slow AVNRT

atria is activated via posterior septum. | VA intervals are short

slow-fast AVNRT with posterior exit

bands of conduction tissue that form an accessory pathway from the atria to ventricles

bypass tracts

bypass tracts generally located in

left or right freewall | septal

bypass tracts conduct

rapidly

antegrade conduction along a bypass tract therefore causes

ventricular preexcitation

bypass tract is localized by examining ____ activation pattern during preexcitation and the _____ activation pattern during _____ conduction

ventricular | atrial

bypass tract is an accessory tract pathway between A and V. tract bypasses

AV node

bypass tract in which the impulse conducts in an antegrade direction

wolf parkison white syndrome WPW

classic sign of WPW is short or slurred PR interval called

delta wave

delta wave indications that venticular activation occured right ____ atrial activation (preexcitation)

after

direction - typically a reentrant impulse travels slow and up fast

orthodromic direction

WPW impusle travels (direction)

antidromic direction

direction - travel down fast byfast fibers and up slower AV conduction pathway (down fast, up slow)

antidromic | WPW

in WPW, bypass tract goes down in order (6)

``` RA, right freewall accessory pathway right bundle branch HIS bundle AV node ```

activation occurs antegrade over the AV node and retrlgrade over the bypass tract

orthodromic conduction

activation occurs antegrade over the bypass tract and retrograde over the AV node Wide QRS

antidromic (WPW)

conducts only in a retrograde direction

concealed bypass tract

concealed bypass tract conducts only in

retrograde direction

concealed bypass tracs are revealed during

ventricular extrastimulus pacing

during a concealed bypass tract ECG visualize

no delta wave | ECG appears normal during sinus rhythm

bypass tract connections can involved (5)

``` atrial myocardium ventricular myocardium AV node HIS bundle bundle branches ```

muscle ridge that connects atrial myocardium to the ventricular myocardium

bundle of kent

most common bypass tract

bundle of kent

connect atrial myocardium to the HIS bundle and completely bypasses AV node

james fibers

bypass tract connects the atrial myocardium to a fascile of a bundle branch

mahaim bypass tract

bypass tracts connect the AV node directly to the ventricle or a fascile. connections are rare

nodoventricular | nodofascicular

bypass tract connect the HIS bundle or Purkinje fibers to the ventricle

Fasciculoventricular

suggested by delta waves that appear to shift axis over time. one bypass dominates and other tracts become significant post ablation

multiple bypass tracts