L19 Flashcards
What is the difference between SVT and paroxysmal?
SVT = constant Parox = comes and goes
What is the measurement for a narrow QRS?
Less than 3 boxes
What does a narrow QRS imply?
Supraventricular tachycardia
B/c indicates ventricular activation is happening via the normal conduction system
What does a wide QRS imply?
Ventricular activation is slow - not happening through normal conduction system (fast)
2 differentials
1. Ventricular tachy - TREAT AS SUCH
2. Supraventricular tachycardia with aberrancy
Which is more worrisome: wide or narrow QRS?
Wide!
Ventricular abnormalities are more likely to be lethal
3 mechanisms of arrhythmias
- Re-entry
- Enhanced automaticity
- Triggered arrhythmias
What is the common mechanism for these arrhymthias: AVNRT, AVRT, Aflutter?
Re-entry
What is the arrhythmia mechanism for Torsade de Pointes?
Triggered - early afterdepol
- During phase 3 of the AP
A 25-year-old male presents to the emergency department complaining of palpitations. He feels anxious, lightheaded, and short of breath. Current EKG reveals a narrow-complex supraventricular tachycardia. Looking back at his medical records, you find a baseline EKG from a prior visit when he had arrived at the ED just following resolution of his symptoms. Baseline EKG is significant for a short PR interval and a wide QRS complex with an initial slurring, or delta wave. Diagnose.
Wolf Parkinson White
- Type of AVRT
= supraventricular tachycardia resulting from pre-excitation of the ventricle due to accelerated conduction along an accessory atrioventricular (AV) pathway that bypasses the AV node
What does a WPW EKG look like?
a wide QRS with initial slurring (delta wave) + sinus rhythm + short PR
- Delta = slurred upstroke of Q-wave as result of partial depolarization prior to normal conduction depolarization
- Wide QRS = extra current is not using the normal conduction system, instead conducting cell-cell = takes longer, widens QRS
- Short PR int = bypassing AV node conduction through atria
What is the arrhythmia mechanism for sinus tachycardia?
Enhanced automaticity
What situation would WPW be lethal?
WPW + Afib
Afib could cause Vfib through bypass tract
What is inappropriate sinus tachy? Pt population? Treat
Young women
Inappropriate response to normal catecholamine release
Get increased atrial HR sitting down
Treat: BB or ablation
3 mechanisms for paroxysmal supravent tachy
- AV nodal re-entrant tachy = AVNRT
- AV reciprocating tachycardia = AVRT
- Atrial tachycardia not from sinus node
Describe AVNRT
Early beat travels to AV node
Blocked in the slow pathway because this pathway is still repolarized from the last normal beat
So this early beat goes down the fast pathway
But by the time it finishes that pathway, the slow option is ready so the current continues in a loop
You only need 1 extra beat to start this - and thus you only need 1 extra beat to stop it
What is the general idea behind AVRT?
There is an additional conduction pathway that bypasses the AV node to connect the atria and ventricles
What is orthodromic supraventricular tachycardia?
Early beat goes through AV node
Abnormal re-entry through bypass tract to re-stim AV node
SEE narrow QRS
What is anti-dromic orthodromic supraventricular tachycardia?
Wide QRS - b/c not using normal conduction
Early beat is block by AV node refractory period
Goes through bypass tract
Comes back up Purk/HIS to re-enter AV node
How do you treat acute paroxysmal SVTs? (AVRT. AVNRT, AT)
Vagal maneuvers to skip 1 beat and reset the system
Adenosine
Cadioversion - only if hemodynamically unstable
How do you treat chronic paroxysmal SVT?
Block AV node = BB or Ca channel blockers
1st choice = ablation = remove the bypass tract or 2nd arm of AV node
What is Aflutter? Describe EKG.
Looping electricity confined to atira
Atria beat at 180-350 bpm with identical, back-to-back atrial depolarization waves = saw tooth!!!
Treat Aflutter
Anticoag + AV node blockers
- BB or Ca channel blockers
- Net slow ventricular rate
Ablation
What is the EKG pattern for AFib?
no discrete P waves
irregularly spaced QRS complexes
- Atria beat at 350-600 bpm with chaotic and erratic baseline (irregularly irregular)
What are you worried about with AFib?
Can cause atrial stasis resulting in thrombus formation may lead to stroke
ANTI COAG ALL PTS
What determines ventricular rate in AFib?
AV node refractory period
Treat AFib?
Rate or rhythm control OR ablation Rate - Ca channel blockers - BB - Ablate AVN, + pacemaker Rhythm - Type 1 or 3 anti-arrhythmics
Which pts do you never give type 1 anti-arrhythmics to?
Pts w/ structural heart disease
What drugs to you give to pts with AFib + decreased LV fxn?
Amiodarone
Dofetilide
(Type 3s)
Where do you ablate for AFib?
Atrial outgrowth around pulm veins
