Narrow Complex Tachycardias (AFib, Aflutter, AVRT, AVNRT) Flashcards
Common tx pathway for all narrow-complex tachycardias (emergency vs. non-emergency)
emergency:
1. ABCDE
2. DC cardioversion
3. Medical cardioversion: dronedarone, amiodarone
non-emergency
1. Carotid massage, vasalva manoeuvre
2. Adenosine, verapamil
Definition of narrow-complex QRS
QRS duration of 120 ms or less
Definition of Afib
Afib: disorganised, rapid and irregular activation in atria, discharge at 300-600bpm, AV node responds intermittently, hence irregular ventrocular rate
Causes and RFs of Afib
Causes: idiopathic, HTN, HF, MI, cardiac surgery
RFs: >60, T2DM, high BP
Signs and Sx of Afib
Sx: chest pain, palpitations, dyspnoea, faintness
Signs: irregularly irregular pulse, apical HR >radial HR
Ix for Afib
ECG:
- absense of P waves
- irregularly irregular rhythm
- lack of isoelectric baseline
Tx for Afib (acute and non-acute, haemodynamically unstable vs stable)
- Identify if acute cause is treatable: alcohol toxicity, chest infection, hyperthyroidism
- Unstable:
- immediate heparin
- attempt cardioversion: synchronised DC shock
- if this fails/Af recurs: IV amiodarone
- then attempt cardioversion again - Stable
- first line: rate control with BBlockers and rate-limiting CCB like verapamil, maybe digoxin
- second line: rhythm control with DC cardioversion + BBlockers, dronedarone or amiodarone
Which AFib medication is avoided in pts with structural heart defects?
Oral flecainide
Which medication is used to prevent thromboembolism in Afib patients?
Aspirin is no longer used
Anticoagulants instead: DOACs like apixaban
Warfarin no longer used as need to monitor INR closely
What is used to calculate stroke risk in Afib patients?
CHA2DS2-Vasc
CHF
HTN
Age >75
Age 65-74
Diabetes
Stroke/TIA
Sex (F)
Vascular disease
Score 1/2 (in Fs): start Tx with NOAC
What score must be used in Afib before DOAC is started?
ORBIT assessment
Definition of Aflutter
Much less common than Afib, organised atrial rhythm with atrial rates of up to 350bpm
Signs ans Sx of Aflutter
Not as well-tolerated as Afib
Palpitations
fatigue
dyspnoea
chest pain
dizziness
syncope
Ix for Aflutter
ECG: regular sawtooth-like atrial flutter waves between QRS complxes - best seen in leads ll, lll and aVF
regularly irregular
What can unmask Aflutter waves on ECG?
Slowing AV conduction by cartoid sinus massage or IV adenosine
Tx for Aflutter + Risk of medically treating Aflutter
Same as Afib (rate and rhythm control, cardioversion)
Risk: as atrial rate slows down from 300, AV node may allow 1:1 conduction, so you MUST monitor pt.
Also consider radiofrequency ablation, very effective
Anticoagulation
What’s the difference between Afib and SVT?
In Afib, atria does not contract –> risk of blood stasis, clots
In SVTs, atria contract excessively fast, so no risk of clots and arrhythmia is relatively benign
What is the pathophysiology of atrioventricular nodal re-entrant tachycardia (AVNRT)
The AV node has 2 pathways:
- slow pathway, with short refractory period
- fast pathway, with long refractory period
In sinus rhythm, impulses travel down both pathways simultaneously.
In pathophysiology, premature atrial contraction arrives while fast pathway is still refractory –> slow pathway takes over –> when premature impulse reaches end of slow pathway, fast pathway is no longer refractory –> impulse recycles retrogradely up fast pathway –> self-sustaining circulation movement, overriding sinus discharge
Difference between AVNRT and AVRT
In AVRT, there’s an accessory pathway that allows impulses to travel antrogradely or retrogradely –> leading to 2 pathways transmitting impulses from atria to ventricles –> setting up re-rentry circuit
What’s an example of AVRT?
Wolff-Parkinson-White syndrome
What are the hallmarks of WPW on an ECG?
Short PR intervals
Wide QRS complex that looks slurred, known as a delta wave
HR 200-300bpm, regular
Tx for AVRT/AVNRT
BBlockers, radio-frequency ablation
