Preexcitation & SVT Flashcards
What are the 2 possible electrical pathways to the ventricles?
- Normal AV node
2. “abnormal” accessory pathways
The most common electrical pathway to the ventricles is through the AV node. The normal AV node to the pathways is referred to as?
alpha pathway
Current can travel through abnormal conduction pathways that are referred to as ______ pathways
beta
Where are the 2 places beta pathways can be found?
AV node
Myocardium
4 other names for the abnormal beta conduction pathways
- accessory pathways
- bypass tracts
- Preexcitation pathways
- Aberrant pathways
normally current travels down the normal ____ _____ ______, because the _____ _____ are usually not dormant/active
av node pathway
beta pathway
If the beta pathways become active for some reason, what is the patient at risk for?
arrhythmias
What are 4 triggers that can activate the beta pathways?
- stress, catecholamine surges
- caffeine, tobacco, street drugs
- electrolyte abnormalities
- acid-base imbalance
When a beta pathway is activated, does the current stop going through the alpha pathway?
no
When a beta pathway is activated, the current will go through (beta, alpha, both) pathway(s)
Both
When current travels down the normal AV node (alpha) pathway it has:
- (slow/rapid) conduction
- (long/ short) refractory period
- SLOW conduction
- slower conduction allows for optimal ventricular filling before ventricular contraction - SHORT refractory period (fast reset)
- the normal AV node pathway does not have to rest long before it can depolarize again (can depolarize faster)
When current travels down the abnormal Beta pathway it has:
- (slow/rapid) conduction
- (long/ short) refractory period
- RAPID conduction
- conduction is faster than the regular AV node path, but still slower than electrical conducting cells - LONG refractory period
- slow reset
What will the PR interval look like if an accessory pathway IN THE AV NODE is activated? (normal, short, or prolonged?)
short PR interval
What will the QRS complex look like if an accessory pathway IN THE AV NODE is activated? (normal or wide?)
normal QRS interval
-the impulse still travels down the normal electrical pathway after the AV node
What will the PR interval look like if an accessory pathway IN THE MYOCARDIUM is activated? (normal, short, or prolonged?)
short PR interval
What will the QRS complex look like if an accessory pathway IN THE MYOCARDIUM is activated? (normal or wide?)
wide; with a delta wave
*The upper ventricle is depolarized by the myocardium and this is slow conduction
*The rest of the ventricle is depolarized by the purkinjie system (fast conduction)
Because current travels faster through the _____ pathways, the ventricles will contract earlier than expected
beta
The term that refers to the ventricles depolarizing earlier than they are supposed to
Pre-excitation
anytime current travels down the _____ pathway, preexcitation will occur
beta
Should we be concerned with pre-excitation from activation of the beta pathway?
What is really the only clinical significance of pre-excitation with an otherwise normal sinus rhythm?
no
the ventricle may just have slightly less optimal filling time; shorter PR interval
(due to earlier ventricular contraction)
If pre-excitation is associated with _____, the abnormal beta pathways can form reentrant loops that can lead to _______
tachycardia
arrhythmias
What is the common arrhythmia that pre-excitation from abnormal pathways can lead to?
supra ventricular tachycardia (SVT)
If a premature atrial contraction (PAC) occurs in a patient with an activated beta pathway, which path will the current travel through to get to the ventricles? The alpha pathway or the beta pathway?
ANTEGRADE through the slow Alpha pathway ONLY
-the accessory pathway from the previous beat is still refractory due to its long refractory period)
When does the accessory pathway repolarize after a PAC?
When the impulse is traveling down the slow AV node
In a PAC:
When the impulse gets to the ventricles (after traveling through the alpha pathway), it can now travel (antegrade/retrograde) through the ______ pathway
retrograde
fast accessory pathway
(the accessory pathway has re-polarized at this point)
In a PAC:
After the impulse has traveled retrograde though the accessory pathway, the impulse can now travel (antegrade/ retrograde) down the _______ pathway
antegrade
slow Alpha pathway
the refractory period is short
The activated accessory pathway in a patient with PAC creates a continuous reentrant _______ loop
tachycardic
What type of arrhythmia does the reentrant tachycardic loop cause?
supra ventricular tachycardia
In PAC with activation of the accessory pathway, the tachycardic loop (re-entry) is in the myocardium, which causes (wide/narrow) QRS and a _____ wave to be seen on the ECG
wide
delta
In PAC with re-entry in the AV node, the QRS will be (normal/wide)
normal (narrow)
a condition in which a patient has an activated accessory path in the myocardium, which forms a direct connection between the atria and ventricle
Wolf Parkinson White Syndrome (WPW)
What is the activated accessory path in the myocardium of Wolf Parkinson White Syndrome called?
“Kent bundle”
In Wolf Parkinson White Syndrome, the Kent bundle is in the (AV node/ myocardium)?
myocardium
Wolf Parkinson White Syndrome shows what 2 things on a ECG?
- short PR interval
- Delta Wave (upward slurring of Q wave)
- The delta wave occurs because the upper ventricle is depolarized by the slow conducting myocardium (via the beta pathway), and the rest of the ventricle is depolarized by the fast conducting Purkinje system (via the alpha pathway)
Wolf Parkinson white syndrome WITHOUT _______ is just preexcitation and is often asymptomatic
tachycardia
If wolf Parkinson white syndrome is present without tachycardia Is treatment required?
no
Since Wolf Parkinson White syndrome can by symptomatic WITH tachycardia, anesthetists should try to avoid ______ stimulation
sympathetic
-ketamine, pain, hypovolemia, anxiety
When WPW syndrome is associated with tachycardia, what other rhythm can it be mistaken for?
Ventricular tachycardia
-QRS is wide
3 treatments for symptomatic Wolff Parkinson White syndrome
- Transvenous catheter ablation
- antiarrhythmic drugs
- beta blockers, amiodarone - Synchronized cardioversion
- if patient is tachycardia and unstable
What treatment for WPW is the most effective and permanent solution
Transvenous catheter ablation
In WPW syndrome, what type of antiarrythmics should anesthetists avoid?
antiarrythmics that block conduction in the AV node
-Adenosine, calcium channel blockers, digoxin
Why must anesthetists avoid antiarrythmics that block the AV node in symptomatic WPW syndrome?
if the AV node becomes blocked, the entire heart signal can travel through the accessory pathway, which can increase the heart rate and precipitate more serious arrhythmias, such as Vfib
a condition in which a patient has an activated accessory path in the myocardium, which forms a direct connection between the atria and the Bundle of His
(bypasses the AV node)
Lown Ganong Levine (LGL) syndrome
What is the activated accessory path in the myocardium called in Lown Ganong Levine Syndrome?
“James bundle”
What 2 things will activation of the James Bundle (LGL syndrome) show on the ECG?
- short PR interval
2. no delta wave
LGL syndrome is normally (asymptomatic/ symptomatic) and (does/does not) require treatment
asymptomatic
does not
a condition in which a patient has an activated accessory path that connects the AV node and the right ventricle by bypassing the bundle of His
Mahaim pre-excitation
What is the accessory pathway in Mahaim pre-excitation called?
Mahaim fibers
What 2 thing on the ECG will Mahaim pre-excitation show?
- Normal PR interval
2. Wide QRS complex that may or may not produce a delta wave
What is the bundle pathway for WPW?
Right atrium to right ventricle
What is the bundle pathway for LGL preexcitation?
Right atrium to Bundle of His
What is the bundle pathway for Mahaim preexcitation?
AV node to right ventricle
a specific type of tachycardia that is greater than 150 beats/min and caused by “reentry”
Supraventricular tachycardia (SVT) -P waves tend to be obscured by the t waves
What 3 things on the ECG are present to clinically classify it as SVT?
- the HR is > 150bpm
- QRS complex is normal
- difficult to differentiate between sinus and junctional tachycardia ( p waves may or may not be present)
Should SVT be treated?
Why?
Yes
-tachycardia reduces ventricular filling time which can greatly diminish cardiac output
SVT is often referred to as _____ SVT reflecting its tendency to begin and end abruptly
paroxysmal
-will need to witness the rhythm speed up on the ECG
What is SVT within the AV node referred to?
AV nodal re-entrant tachycardia (AVNRT)
What rhythm is the most common type of re-entry?
AVNRT
What 2 things does the ECG for AVNRT show?
- narrow QRS complex
2. may or may not have a p wave
How should we treat AVNRT?
slow conduction through the AV node
What are 5 ways we can slow conduction through the AV node?
- vagal maneuvers
- adenosine
- calcium channel blockers
- Sotalol
- Digoxin
What are 3 ways to achieve a vagal maneuver?
- Blowing through a straw
- Carotid sinus massage
- cold stimulus
In which patient population should you avoid a carotid sinus massage
Geriatric population or patients with high cholesterol or previous stroke
-dangerous and could dislodge a plaque
Adenosine is (short/long) acting and (comfortable/uncomfortable) for the patient
short (5-10 seconds)
uncomfortable (can stop the patients heart)
What are the dosing guidelines for adenosine?
initial 6 mg bolus (followed by NS flush)
then up to 2 additional doses of 12mg
What is Sotalol?
What rhythm is it indicated to treat in ACLS?
Beta blocker that blocks conduction through the AV node
-increases the refractory period
indicated to treat SVT
What is the dose for Sotalol?
100mg or 1.5 mg/kg
In which patients should Sotalol be avoided?
Patients with prolonged QT syndrome
What are the 5 treatments for SVT within the AV NODE?
- slow conduction through the AV node
- vagal maneuvers, adenosine, calcium channel blockers, digoxin - antiarrythmics
- amiodarone - Beta Blockers
- Sotalol - Synchronized cardioversion
- Transvenous catheter ablation
What is SVT in the myocardium referred to?
Atrioventricular Reentrant Tachycardia (AVRT)
What does the ECG for AVRT show?
Delta waves
What is the relationship between WPW syndrome and AVRT?
WPW syndrome can become AVRT
- a kind of AVRT
WPW is the disease and AVRT is the symptom
4 treatments for SVT in the myocardium (AVRT)
- antiarrythmics
- amiodarone - Beta blockers
- synchronized cardioversion
- Transvenous catheter ablation
What type of drugs should you avoid in AVRT? (accessory pathway through the myocardium
blockers through the AV node
-blocking antegrade conduction through the AV node may promote rapid conduction through the bypass tract and develop VT/VF
What are the 2 treatment differences between AVNRT and AVRT?
AVRT should not be treated with vagal maneuvers or drugs that slow conduction through the AV node
When is catheter ablation for SVT used?
When patients have arrhythmia such as Afib that are unresponsive to medications
What is the mechanism of catheter ablation for SVT?
The surgeon maps out the area of the heart that is causing the arrhythmia and ablates the abnormal conduction pathways
What is the purpose of the Maze procedure?
To treat Afib
a procedure that inflicts scar tissue through a variety of possible means (incisions, cold temperatures/cryomaze, ablation lines, etc)
Maze procedure
- scar tissue disrupts abnormal conduction pathways
- usually combined with another heart procedure
What is the purpose of the left atrial appendage closure?
to prevent clot release from the left atrium in patients with a hx of atrial fibrillation
What are 2 options for a left atrial appendage closure?
- Ligation of left atrial appendage
- during open heart surgery - Insertion of the Watchman device
- endovascular operation
