Arrhythmias: Treatment 2 Flashcards
Name 3 rhythms most commonly considered supra ventricular arrhythmias, plus 2 extras often separated out.
Supraventricular arrhythmias
Paroxysmal supra ventricular tachcardias (PSVT)
- AV nodal reentry tachycardia (AVNRT)
- AV reentry tachycardia (AVRT) - includes WPW and AV reentry through concealed bypass tract
- Atrial tachycardia
- Atrial fibrillation
- Atrial flutter
Describe the two pathways available for conduction in AVNRT and how they are different.
there is a both a slow and a fast pathway in the AV node
fast pathway has a long recovery time
slow pathway has short recovery time
analogy of boats and wakes applies here
Describe the situation when AVNRT dual conduction pathway becomes problematic. Is it triggered or a constant problem?
during normal sinus beats fast pathway depolarizes the AV node and it is refractory to the slow pathway so normal AV and ventricular depolarization occurs
during premature atrial contraction the fast pathway is still refractory while the slow pathway may permit depolarization which both depolarizes AV node and ventricles but also sets up a reentrant pattern that the depolarization can then travel down the slow pathway again, creating a loop
- What are possible signs on an ECG of AVNRT? How could you terminate AVNRT?
possible to see retrograde P-waves in leads I, II, V1-V3, these p waves may be buried in the QRS itself
can terminate with a properly timed PAC or PVC which leaves part of the reentry loop refractory or increase the refractory time of the AV node (meds ie. adenosine)
AVNRT can be treated permanently by destroying the cells of the slow pathway via ablation
Where are the possible positions of accessory pathways (AVRT) and what disorder is directly connected to conduction through these pathways?
right-sideded, left-sided, posteroseptal or anteroseptal
patients with Wolff-Parkinson-White syndrome have accessory pathway that can conduct in both an anterograde or retrograde direction (retrograde conduction only is considered ‘concealed’)
What are the diagnostic criteria for WPW syndrome, a type of AVRT? (4.5)
- PR interval of 100ms
must also be found with tachycardia
How is AVRT initiated?
PAC conducts through AV node but not accessory path that is refractory
retrograde conduction through the accessory pathway curs causing a reentrant loop tachycardia ( and inverted Pwave and short R-P interval)
Why are patients with WPW at particular risk of sudden cardiac death and how might you treat AVRT?
atrial arrhythmias such as atrial flutter and atrial fibrillation can conduct rapidly over the accessory pathway and elicit extremely rapid ventricular rates (degrades into ventricular fibrillation)
treatment with radio frequency ablation of the accessory pathway often indicated with patients with WPW
What is the cause of atrial tachycardia and what are ECG findings with atrial tachycardia?
focal tachycardia located in atrial muscle outside the AV or SA node (single or multi focal)
Pwaves are clearly discernible and PR interval is normal, Pwave morphology may be abnormal
How is atrial tachycardia treated?
mapping and ablation of the ectopic focus; area of early depolarization in the atria is targeted for ablation
Atrial flutter F waves would be expected to be upright on which leads?
V1
deflection on II, III and aVF
What area would you aim to ablate in order to interrupt a flutter circuit.
ablation of the tricuspid isthmus, creating a block of the circuit
What is the ECG signature of atrial fibrillation?
rapid, irregular p waves; p waves may not be discernible
irregularly irregular R waves; note AF may result from degradation of PSVT
Describe different approaches to ablation of atrial fibrillation.
isolation of pulmonary venous focus ie. via ballon ablation
FIRM- focal impulse and rotator modulation: disorganized electrical patterns caused by organized rotors or focal sources
In our patient with arrhythmogenic right ventricular displasia who presents with frequent ICD shocks and failed ablation, what is the course of action?
further ablation within scarred areas to prevent arrhythmias from scarred areas exiting through transitional zone and creating ventricular arrhythmia
