Arrythmias Flashcards
What is an arrhythmia?
An abnormality in the rate and/or rhythm of the heart
Name the groups of arrhythmia?
- Cardiac arrest rhythms
- Narrow complex tachy rhythms (AF, A flutter, SVT)
- Broad complex tachy rhythms (VT, SVT with bundle branch block)
Name the cardiac arrest rhythms and whether or not they’re shockable.
Shockable
- VT
- VF
Not Shockable
- PEA
- Asystole
How is a tachycardic rhythm treated if the Pt is unstable?
- Up to 3 synchronised shocks
- Consider amiodarone infusion
How is a stable patient treated with tachycardic rhythm?
- AF- Beta-blocker (or diltiazem CCB)
- Flutter- Beta-blocker
- SVT- Vagal manoeuvre e.g. valsalva and adenosine
- VT- amiodarone infusion
- SVT bundle branch block- vagal manoeuvre and adenosine
What causes atrial flutter?
Re-entrant rhythm
- self-perpetuating loop due to an extra pathway
What is the atrial and ventricular rate in a flutter?
Atrial = 300BPM
Ventricular = 150BPM
What does an ECG show in flutter?
- Saw tooth appearance (P wave followed by P wave)
Which conditions are associated with flutter?
- HTN
- Ischaemic heart disease
- Cardiomyopathy
- Thyrotoxicosis
How is flutter treated?
- Rate control (beta-blocker) or cardioversion
- Radiofrequency ablation of the re-entrant rhythm
- Anticoag (CHA2DS2VASc)
What is an SVT?
- Electrical signal re-enters the atria from the ventricle
- Travels back through the AV node into the ventricle again, causing a second contraction from the same impulse
- Self-perpetuating loop (AVN-Vent-AVN-Vent…)
What does an ECG show in SVT?
- QRS, T wave, QRS, T wave…
What are the three types of SVT?
- Atrioventricular nodal re-entrant tachy (impulse goes back through the AVN)
- Atrioventricular re-entry tachy (accessory pathway e.g. Wolff-Parkinson-White)
- Atrial tachy (ectopics)
How are SVTs acutely managed in a stable patient?
- Continuous ECG
- Valsalva manoeuvre
- Carotid sinus massage
- Adenosine or Verapamil
- DC cardioversion if all else fails
How does adenosine work?
Slows conduction at the AVN, resetting sinus rhythm, causes brief asystole/bradycardia before it is quickly metabolised
When is adenosine CI?
- Asthma
- COPD
- HF
- Severe hypotension
What dosing of adenosine is used IV?
6mg, then 12mg, then 12mg if no improvement
What is the long-term treatment of SVT?
Medication
- Beta-blocker/CCB/amiodarone
Radiofrequency ablation
What is the cause of Wolff-Parkinson-White?
Accessory pathway- the Bundle of Kent
How is WPW treated definitively?
Radiofrequency ablation of the Bundle of Kent
What ECG changes are seen in WPW?
- Short PR (<0.12s)
- Delta wave (rising up into QRS)
- Wide QRS (0.12s+)
What is Radiofrequency Ablation?
1- Catheter in the femoral vein, fed on a wire through to the heart under XR guidance
2- In the heart, it is placed against different parts to test for electrical signals
3- Once an accessory is found, the ablation (heat) is applied to burn the area, and the scar tissue cannot conduct
What is Torsades de Pointes?
Polymorphic VT- ‘twisting of the tips’
- QRSs get smaller and smaller, then big and smaller and smaller…
- Seen in long QT
What causes Torsades de Pointes?
Long QT- prolonged repolarisation
- High risk of early afterdepolarisation
What can Torsades de Pointes lead to?
- Either spontaneously return to sinus
- Or cause VT, cardiac arrest and sudden death
What can cause a long QT?
- Long QT syndrome (inherited)
- Medication- citalopram, flecainide, sotalol, amiodarone, macrolide ABx e.g. clarythromycin
- Electrolytes- hypokalaemia, hypomagnesaemia, hypocalcaemia
How is Torsades de Pointes treated?
- Treat cause e.g. electrolytes/medication
- Magnesium infusion even if normal Mg
- Defibrillate if VT
How is prolonged QT managed long-term?
- Avoid medications that prolong QT
- Correct electrolytes
- Beta-blockers (but not sotalol)
- Pacemaker or implantable defib
What are ventricular ectopics?
- Premature ventricular beats
- Present as random, brief palpatations
- Common at all ages, even if healthy, but more so in pre-existing heart conditions
What is bigeminy?
Ventricular ectopics so frequently that they occur after every sinus beat
ECG: P, QRS, QRS, P, QRS, QRS, P…
How are ventricular ectopics managed?
- Check for anaemia, electrolytes, thyroid function
- Reassure if patient is healthy
- Refer if FHx of sudden death, background of heart disease etc.
What are the types of AVN heart block?
- First degree
- Second degree (Mobitz Type 1/Wenckebach’s and Mobitz Type 2)
- 2:1
- Third degree
What is first degree heart block?
- Every impulse gets through AVN but is delayed, no QRS dropped
ECG: over 0.2s PR
What is M Type 1/ Wenckebach’s?
- Impulses gradually weaken before one isn’t conducted through the AVN
ECG: Progressively long PR, QRS drops, then restarts
What is M Type 2?
- Intermittent failure of the AVN to conduct
ECG: prolonged PR, consistent, then a random QRS drops
What is Third degree block?
- Complete AVN block
- Ventricular escape rhythm
What is 2:1 block?
- Every other impulse doesn’t get through
ECG: P, QRS, P, P, QRS (every other QRS dropped)
Which heart block has an asystole risk?
- Third Degree (highest)
- Mobitz Type 2 (moderate)
How are Types 1, Wenckebach’s and 2:1 treated if stable?
Observation
How are unstable patients or asystole risk (M Type 2, Third degree) treated?
Atropine 500mcg IV
No improvement- repeat up to 6 doses/3mg
Then, use another inotrope e.g. noradrenaline
How might an asystole risk be treated long-term?
Pacemaker
How long do pacemaker batteries last?
5 years
What can’t you do with a pacemaker?
- MRIs may be CI (newer ones are compatible)
- Diathermy and TENS in surgery
How can you tell what type of pacemaker is in place on an ECG?
*Important for exams
Single chamber (RA or RV only)- Vertical black line before the P wave or QRS
Dual chamber (RA and RV have leads)- Vertical black lines before both P and QRS
