Download Cardiac Electrophysiology

©2009 Mark Tuttle
Cardiac conduction
- Sinus node in the high right atrium
- Really isn’t a sinus “node, just a rough area where you might find it
- 2/3 down the right atrium  crista terminalis, area where you will find the SA
- At higher HR, signal comes frop top of crista terminalis
- At lower HR, signal comes from low crista terminalis
- Thus, the SA node isn’t just one area
- Inappropriate sinus tachycardia: people who run consistently high sinus rates
100-130 bpm 24/7
- To treat, “burn out” top of crista terminalis
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Bachman’s bundle: a piece of CT which connects R and L atrium
AV node: not really one spot
Leans over to the R side of the heart (but uncommonly on Left)
Eustacian bridge: from
Hook’s triangle tricuspid valve, septum, Eustachion bridge
AV node is within this triangle
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R bundle branch is usually a well defined area
L bundle is usually harder to find – more like a spider web – more diffuse
Arrythmia correction
- catheter of precoridal electride
- in coronary sinus
- go behind the L atrium
- in ECG: if catheter in atria, just see atrial signal, in ventricle see ventricle signal 
can tell where you are
- when you are at the Bundle of His
o see wave for atria and wave for ventrical with a small “H” wave in
between
o QUESTION on test: AH interval is time it takes to go from SA – AV
o HV interval is time from AV node down
o H stands for His
o Which is less bad: HA interval prolongation because not as bad as HV
conduction  worry more about conduction distal to AV node. Ex atrial
fibrillation isn’t as bad
- Coronary sinus catheter use as surrogate for measuring L atria since it is right
behind the L atria
- If you block coronary sinus  nothing happens! Reroutes blood, this it is fine to
throw a catheter in there
“Double AV nodes”
- Can go back between through AV node  conduction problem
- Conduction can go backward!
©2009 Mark Tuttle
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Wenckebach “Wachy” block: PR interval is short, longer, longer, then wont
conduct, gets progressively worse (not on test)
AH starts getting longer and longer
This is a normal function of the AV node
**AV Node reentry: most common rhythm problem
 you have 2 AV nodes
25% of people have split AV nodes  have potential for this rhythm to happen
Essentially, conduction goes down one av node and comes back up the other,
and then back down again to ventricles
Get endless loop
Heart rates will be 200bpm
Treatment: take one AV node out (whichever one which conducts worse)
Usually 1 right by septum/ his
Other one usually by coronary sinus opening
Can be very close to each other  take out both, then need pacemaker
if you have normal sinus node, and you stop pacing (with a pacemaker) it, it
should “wake up” and start pacing again
if you have a diseased SA node, won’t wake up right away
if it’s diseased, takes longer to wake up
Ventricular tachycardia
- this is bad: can kill you
- get from heart attach damage
- young people can get it too (not lethal)
- Ventricle going very fast, atria not going fast, essentially disconnected
Atrioventricular Nodal Reentry Tachycardia (AVNRT)
- Most common cause of Paroxysmal Supraventricular Tachycardia (PSVT) in
adults
- Typical accounts for 80% of castes
- Split AV nodes
- A2-H2 = 130ms
- A2-H2 = 230ms (remove this one b/c it doesn’t conduct as well)
EP study: catheters- AP
- catheter at septum, areas between 2 AV nodes may be especially small in small
children
- in this case, “freeze” one of them with catheter to disable it (instead of surgery)
LAO (left anterior oblique)
- d
©2009 Mark Tuttle
Can go down on R atrium and then (reenter) and come back and go to L atrium
- detect with trans septal catheter (goes through to L atrium)
Atrial tachycardia
- can be anywhere in atrium
- Use an Avix – looks like party balloon
- Put it in the atrium, blow it up with radio opaque liquid
- Is coated with electrodes – records along entire outside surface
- Will tell you exactly where it sees signal – where it first sees signal
Atrial flutter
- common rhythm failure
- Conduction loop within atria
- P waves continuous
- Signal goes around crista terminalis and Eustachian ridge and back up
- Burn/freeze an area of this conduction by the Vena Cava – easiest spot to break
the conduction loop
- Can make a computer map of this
- If you leave a gap (even if it is small), signal will continue. Need complete
ablation
o Really need to damage entire area so it doesn’t sneak through
- For corrections in the L atrium -> much more difficult
- Pulmonary veins come in – often irregular arrangement (less than 4)
- Get L atrial drawing on computer to see their anatomy
- Can take crossections too
- When doing these analyses, need to be mindful of tamponade (piercing
pericardium and bleeding into pericardial space)
- Pulmonary veins are outside the pericardium – get free bleeding not tamponade
Case #1: Cardiomyopathy (Primary or Secondary to Left Bundle Branch Block)
- Patient with frequent palpitations and dyspnea
- Had cardiomyopathy
- Evaluation shows left ventricular hypertrophy
- EKG
o See left bundle branch block
o Premature ventricular conductions (PVCs) are coming from R ventricle
o Could be because she has cardiomyopathy
o Could be causing cardiomyopathy
- Problem: irritated spot in ventricle: generating frequent (premature ventricular
conduction) PVCs (1000/hr)
- Pumping is disrupted by the PVCs
- Treatment: find the spot and cauterize it
- R ventricle is large: need computer to help guide it
©2009 Mark Tuttle
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If you’re looking down at the heart
Right ventricular outflow tract (RVOT)
Aorta is close to pulmonary artery
If you have a rhythm problem coming from pulmonary artery, could be from
there or could be from aortic valve area because there is conduction tissue there
Problem with cauterizing aortic area: opening of coronary arteries is there
Diagnose: pacemaker from that spot: see if her natural EKG waveform looks the
same, if so: that is the source of the ectopic pacing  need to cauterize that
area
After treatment (ablatement of the actopic spot)
o Ejection fraction went up to 50%
o A good success story
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Case #2: Atrial Flutter
- Patient status post cardiac bypass
- Atrial flutter refractory to medical therapy
- EKG
o See flutter wave (lots of P waves – look like teeth)
o See roughly 4 P waves for each QRS (ventricular contraction)
o Not conducting down the AV node very quickly
- Crista Terminalis is roughed up – called “Ring of Fire”
- See a lot of arrhythmias originating here because anatomy is so variable
- Get a continuous conduction loop here, occasionally successfully propagates
down into ventricles
- If you want to fix this, go to the valve, and burn/freeze the area
- Pectinate muscles are in the way – tough/thick difficult to get through them
- Area between the thebsian valve and the IVC: Cozio’s isthmus
- Voltage map (computer)
o Look at size of voltage  if successfully burned off – no signal,
successfully damaged
o Can check for gaps in ablation
o First ablation was unsuccessful probably because pectinate muscles got
in the way
o With the computer voltage map, can see exactly where the conduction is
getting through  ablate that area with ablation catheter
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