Arrhythmias Flashcards
What is an arrhythmia?
Abnormal heart rhythm
Why do arrhythmias occur?
Result of an interruption to the normal electrical signals that coordinate contraction of the heart muscle
How many cardiac arrest rhythms are there?
4
What type of patients are cardiac arrest rhythms seen in?
Pulseless, unresponsive ones
-Can be categorized as shockable or non-shockable
Types of shockable cardiac arrest rhythms?
Ventricular tachycardia
Ventricular fibrillation
Types of non-shockable cardiac arrest rhythms?
Pulseless electrical activity
Asystole
Treatment of tachycardia in an unstable patient?
3 synchronized shocks
-Consider amiodarone infusion
Categories of stable patients with tachycardia and their treatments?
Narrow complex QRS:
- A fibrillation= Rate control (beta blocker/diltiazem)
- Atrial flutter = Rate control with beta blocker
- Supraventricular tachycardia= vagal manoevres and adenosine
Broad complex QRS:
- Ventricular tachycardia = amiodarone infusion
- SVT with bundle branch block= treat as normal SVT
- Irregular= seek help
What causes an atrial flutter?
Re-entrant rhythm in either atrium
-E. signal circulates in self-perpetuating loop due to an extra electrical pathway in atria
without interruption
What is the atria contraction BPM in atrial flutter?
300bpm
What causes a ventricular contraction of 150bpm in atrial flutter?
The electrical signal makes its way out of atria into ventricles every 2nd loop due to long refractory period of AV node
What does an ECG of atrial flutter look like?
Sawtooth appearance
P wave after p wave
Conditions associated with atrial flutter?
Hypertension
IHD
Cardiomyopathy
Thyrotoxicosis
Treatment of atrial flutter?
Rate/rhythm control: B blockers
Treat reversible underlying condition (eg HT)
Radiofrequency ablation of reentrant rhythm
Anticoagulation based on CHA2DS2Vasc score
How long is a broad QRS complex?
> 0.12s
How long is a narrow QRS complex?
<0.12s
What causes supraventricular tachycardia?
Electrical signal re-entering atria from ventricles
Journey of signal in supraventricular tachycardia?
-Signal finds way back into atria
-Once in, it travels back through AV node & causes another ventricular contraction
-Causing elf-perpetuating loop without an end point
=
Resulting in narrow complex tachycardia
What doe SVT look like on an ECG?
QRS complex followed immediately by T wave
What is paroxysmal supraventricular tachycardia?
Where SVT reoccurs and remits over time
3 main types of SVT?
Atrioventricular nodal re-entrant tachycardia
Atrioventricular re-entrant tachycardia
Atrial tachycardia
What is AV nodal re-entrant tachycardia?
Re-entry point is back through the AV node
What is AV re-entrant tachycardia?
Re-entry point is an accessory pathway (Wolff-parkinson-white syndrome)
What is atrial tachycardia?
Electrical signal originates in atria somewhere other than SA node (not caused by signal re-entry from ventricles). Instead from abnormally generated electrical activity in atria
What does atrial tachycardia cause atrial rate to become?
> 100bpm
What to ensure when treating SVT patients?
That they are continuously monitored on ECG
Treatment of SVT?
- Valsalvia manouevre
- Carotid sinus massage
- Verapamil (CCB) (alternative to adenosine)
- Adenosine
- Direct current cardioversion
What is the valsavia manouevre?
Patient blows hard against resistance eg plastic syringe
What is carotid sinus massage?
Massage carotid on one side gently with 2 fingers
What does adenosine do in SVT?
Slows cardiac conduction through AV node. Interrupts AV node/accessory pathway during SVT and resets to sinus rhythm
How would adenosine be given in SVT?
Rapid IV bolus
What can adenosine sometimes cause when treating in SVT?
Brief period of asystole or bradycardia however sinus rhythm will be restored in time
When to avoid prescribing adenosine?
-Patient has asthma, COPD, HF, heart block, hypertension
How to treat paroxysmal SVT?
Medication (Bb, CCB, or amiodarone)
Radiofrequency ablation
What causes wolff-parkinson-white syndrome?
Extra electrical pathway connecting atria and ventricles. Normally only 1 pathway called AV node but extra in this syndrome called the bindle of Kent
Treatment of WPWS?
Radiofrequency ablation of accessory pathway
What WPWS looks like on an ECG?
- Short PR interval
- Wide QRS complex
- Delta wave (slurred upstroke on QRS complex)
What consists of a short PR interval?
<0.12s
What is a delta wave?
Slurred upstroke on QRS complex
When are anti-arrhythmatic drugs contraindicated?
Patients with WPWS + AF/Aflutter
-increases risk of torsades de pointes
Which conditions is radiofrequency ablation curative for?
AF
A flutter
SVT
Wolff-parkinson-white syndrome
What is Torsades de pointes?
Polymorphic ventricular tachycardia
What does Torsades de Pointes look like on ECG?
Normal ventricular tachycardia except there is the appearance of the QRS complex twisting around base line
QRS height gets progressively shorter the larger then repeats
Physiology of torsades de pointes?
- Prolonged repolarization of muscle cells in heart after contraction
- Repolarization is period of recovery before myocytes are ready to depolarize again
What can longer repolarization result in?
Random spontaneous depolarization in some areas = afterdepolarisations
These spread through ventricles leading to another ventricular reaction prior to proper repolarization occurring
What causes prolonged QT waves?
- Long QT syndrome (inherited)
- Medication (antipyschotics, citalopram, flecainide, sotalol, amiodarone, macrolide ABs)
- Electrolyte disturbances eg hyperkalaemia, hypomagnesamia, hypocalcaemia
Acute management of torsades de pointes?
Correct cause eg EL disturbance/meds
Mg infusion
Defibrillation if VT occurs
Chronic management of TDP?
Avoid meds that prolong QT
Correct electrolyte disturbance
B blockers
Pacemaker/implantable defibrillator
What are ventricular ectopics?
Ventricular premature beats
Why do ventricular ectopics happen?
Random electrical charges from outside atria
Presenting complaint of someone with ventricular ectopics?
Random brief palpitations
What an ECG of ventricular ectopics shows?
Individual, abnormal, QRS complexes on background of normal ECG
What is bigeminy?
When ventricular ectopics occur after every sinus beat
Management of ventricular ectopics?
Check bloods for anaemia, EL disturbances & thyroid weirdness
-Reassurance and no treatment in otherwise healthy patients
1st degree AV node heart block?
Delayed AV conduction through AV node
Every atrial impulse leads to V contraction (every P gives a QRS)
ECG shows PR interval as more than 0.2s
Husband coming home late every night same time
What is a prolonged PR interval?
0.2s
2nd degree AV node heart block?
- Some atrial impulses do not make it through AV node to ventricles
- Some p waves don’t lead to QRS complexes
The husband keeps coming home progressively later and later until he doesn’t come home at all
3 types of 2nd degree heart block?
- Wenckebach’s phenomenon: Mobitz 1
- Mobitz type 2
- 2:1 Block
Describe Mobitz 1?
Atrial imput becomes gradually weaker until doesn’t pass through AV node
After failing to stimulate V contraction the P wave returns to strength again
What does an ECG show in Mobitz 1?
Increasing PR intervals until P wave no longer conducts to ventricles (absent QRS)
What is Mobitz type 2?
Intermittent heart failure
Results in missing QRS complexes
Ratio of P waves to QRS complexes is usually 3:1 block
PR interval remains normal
What is 2:1 block?
2 p waves for every 1 QRS complex
Every 2nd P is not strong enough
Can be caused by M1 or M2
3rd degree heart block?
Complete heart block
No observable relationship between P waves and QRS complexes
Which two types of heart block have significant risk of asystole?
3rd degree AV nodal heart block
2:1 block
Treatment of bradycardia in an unstable patient?
1st line: atropine 500mcg IV *no improvement* Atropine 500mcg Other inatropes (noradrenalin) Defibrillator
Side effects of atropine?
Dilated pupils
Urine retention
Constipation
Dry eyes
How does atropine work?
Antimuscarinic
-Inhibits parasympathetic nervous system
