Arrhythmias Flashcards
Define atrial fibrillation and atrial flutter
AF: disorganised, chaotic atrial activity with random ventricular conduction
Flutter: organised atrial activity with variable conduction to ventricles, often in 2:1, 3:1, 4:1 pattern
Describe the presentation of AF
- Usually older patients
- May be asymptomatic or symptomatic
- Presents w palpitations, SOB, chest discomfort, dizziness, syncope, HD unstable
Name the causes of AF
Idiopathic: Lone AF Cardiac: valve disease, IHD Pulmonary causes: PE, pneumothorax Metabolic: alcohol use, thyrotoxicosis, electrolytes Infection: sepsis
Describe the ECG findings in AF
-Irregularly irregular (rhythm)
-Narrow complex (QRS)
-Tachycardia (rate)- not always
+ absent p waves
Describe the assessment and initial management of acute AF
- A to E approach if HD unstable
- Investigations:
- ECG
- Bloods: FBC, CRP, U+Es, TFTs, glucose, troponins, clotting
- Imaging: CXR - Acute Management:
- If started within 48 hours: rate/rhythm control + anticoagulate w LMWH
- If HD unstable: DC cardioversion + anticoagulate (LMWH)
What are the options for rate and rhythm control in AF?
Rate control:
- Beta-blockers (bisoprolol, metoprolol): avoid in asthma
- CCBs (diltiazem, verapamil): avoid in HF
- Digoxin
Rhythm control:
- Pharm: flecainide, amiodarone (structural heart disease, IHD)
- Non-pharm: DC cardioversion
Describe the long term management of AF
ABCs of AF:
A: Avoid stroke/Anticoagulation
-CHADS-VASc vs ORBIT for decision making
*Offer if 2+ score or consider if male and 1+
-Non-valvular AF: DOACs (apixaban, rivaroxaban)
-Valvular AF: warfarin
B: Better symptom control
-Rate control or rhythm control
C: CVS risk reduction
- Diet + exercise, smoking cessation, alcohol reduction
- Statin
- BP control, DM control
When would you consider rhythm control in management of AF?
- Acute AF (started within 48 hours)
- HD unstable -> DCCV
- Symptomatic on/refractory to rate control
Describe the management of AF presenting over 48 hours after onset
- Consider cardioversion if suitable
- Anticoagulate for 3 weeks prior and continue after
- Elective TOE guided DCCV > pharm
- Consider amiodarone prior to and following DCCV to maintain - Rate control for permanent AF/unsuitable for CV
- Pill-in-pocket for infrequent paroxysmal AF
Describe the CHADS-Vasc score
CCF (1) HTN (1) Age >65 (1), >75 (2) Diabetes (1) Sex F (1) Stroke or TIA (2) Vascular disease (1)
Name some complications of AF
- Stroke
- Heart failure
- Death
- Complications of treatment
Describe the management of atrial flutter
Similar to AF
- If HD unstable: DCCV
- If acute onset (48 hours): rate or rhythm control. Best is electrical rhythm control. Anticoagulate.
- If >48 hours: rate control, anticoagulate. Consider long term rhythm control.
What are the signs of HD instability?
Shock
MI
Acute heart failure
Syncope
Describe atrial flutter on ECG
- Regular
- Narrow complex
- Tachycardia (ventricular rate about 150bpm)
- 2:1/3:1 etc AV block
Define SVT
Any tachycardia in which the electrical activity arises from above the ventricles (narrow complex tachy)
What are the types of SVT?
- Sinus tachycardia
- Atrial: AF, flutter, atrial tachycardia
- AVNRT
- AVRT
What is the difference between AVNRT and AVRT?
AVRT occurs when there is an anatomical accessory pathway allowing electrical impulses to re-enter the atria.
AVNRT: functional re-entry circuit within the AV node
Describe the presentation of AVNRT
-Common demographic is young women w normal hearts
-Causes paroxysmal rapid regular palpitations, syncope, chest pain, SOB, anxiety
-
Describe the pathophysiology of AVNRT (slow-fast)
- AV node has fast and slow pathways
- Electrical impulse enters node and travels down fast pathway. This pathway then has to repolarise
- If a new impulse enters the node (PAC), this will travel down the slow pathway bc fast is busy repolarising
- By the time the impulse has travelled the slow path, the fast is done repolarising -> impulse travels the wrong direction up the fast.
- Continual re-entry occurs
Describe the ECG in AVRT and AVNRT
AVNRT:
- Narrow complex tachycardia (140-280bpm)
- Absent (slow-fast) or inverse p waves after the QRS (fast-slow)
- May have widespread ST depression
AVRT:
- Narrow complex tachycardia (200-300bpm)
- Buried p waves
- Possible ST depression, T wave inversion
- When controlled, may reveal WPW
BASICALLY THE SAME
What is WPW?
The presence of an accessory pathway between the atria and ventricles (Bundle of Kent) that can result in SVT (AVRT)
Describe the management of acute SVT
- HD unstable: DCCV
- Vagal manoeuvres (carotid massage, Valsalva, ice cube)
- Adenosine 6mg IV bolus -> 12mg -> 12mg
- Digoxin, amiodarone, beta-block, CCB
Describe the long term management of SVT
Conservative: avoid stimulants, alcohol
Pharmacological: flecainide, beta-blockers
Surgical: ablation
Describe VT on ECG
- Regular, broad complex tachycardia
- Monomorphic or polymorphic (Torsade des Pointes)
Describe VF on ECG
Chaotic activity, no organised complexes
Name the causes of VT/VF
- Ischaemic heart disease
- Structural heart disease
- Electrolyte abnormality
- Drugs/toxins
- Congenital heart disease
Describe the presentation of VT/VF
- Non-sustained VT: paroxysmal palpitations, syncope, chest pain, SOB, etc
- Cardiac arrest
- Sudden cardiac death
Describe the management of in hospital cardiac arrest
Put out a 2222 cardiac arrest call
- Start CPR- 30:2 at 100-120/s
- Protect airway and give high flow O2
- Gain IV access and take bloods
- FBC, CRP, U+Es, clotting, troponin, glucose - Defibrillate when available if shockable rhythm (pulseless VT/VF)
- Administer shock, continue CPR for 2 mins. Repeat 3x
- Adrenaline 1mg of 1:10,000 after 3rd shock and then every alternate shock (3-5 mins)
- Amiodarone 300mg after the 3rd shock - If non-shockable rhythm, continue CPR and reassess
- Give adrenaline and amiodarone as per shockable
What are some causes of cardiac arrest?
4 Hs and 4Ts Hypoxia Hypothermia Hypovolaemia Hypo/hyperkalaemia/metabolic
Thrombosis
Tamponade
Toxins
Tension pneumothorax
Describe the acute management of sustained VT (not cardiac arrest)
A to E approach
- IV access and bloods
- Continuous cardiac monitor
1. If HD unstable: sedate and DCCV with amiodarone
2. If HD stable: amiodarone loading dose (300mg over 20-60 min, then 900mg over 23 hours)
3. Correct any hypokalaemia or hypomagnesaemia
4. Consider need for ICD
What are the types of bradycardia? How do they appear on ECG?
- Sinus bradycardia
- Heart block
- 1˚: prolonged PR interval
- 2˚ Type 1: prolongingly prolonged PR interval with dropped QRS
- 2˚ Type 2: prolonged PR interval with dropped QRS
- 3˚/complete: no assoc between ps and QRSs - Bundle branch block:
- LBBB: W in V1, M in V6
- RBBB: M in V1, W in V6
- Trifascicular block: 1st degree heart block, RBBB, LAD
How are pacemakers described?
3 letters:
1st: paced chamber (A/V/D)
2nd: sensing chamber (A/V/D)
3rd: response to sensed event (Inhibit/Trigger/Dual)
What are the indications for permanent pacing?
- Persistent bradycardia without correctable cause
- High degree blocks: Type 2 2nd˚ block, 3˚ block
- Symptomatic AV block (any degree)
- Various others: NMJ diseases, cardiomyopathy, etc
Describe a system for interpreting ECGs
- Rate: fast or slow?
- Rhythm: regular or irregular?
- Axis: LAD, RAD
- p waves: present? Assoc w each QRS?
- PR interval: prolonged or shortened?
- QRS: narrow or broad?
- ST segment: elevated or depressed?
- T wave: inversion?
- QTc: prolonged?
Name some causes of QTc prolongation
Toxins: -TCAs -Amiodarone Ischaemia Mitral valve prolapse Electrolyte abnormality (low K, Mg, Ca)
What is a normal axis? RAD? LAD?
-30 to 90
LAD: -30 to -90
RAD: 90 to 180
How do you assess the axis?
Look at leads I and II:
- If both +: normal
- If I is - and II is +: RAD
- I + and II -: LAD
What is a normal PR interval?
0.12-0.2s OR 3-4 small squares
What is a normal QRS width?
<0.12s or 3 small squares
What is a normal QTc?
0.38-0.42s
What are the signs of LVH on ECG?
Tall R wave in V1, deep S wave in V6
What is electrical alternans a sign of?
Cardiac tamponade
How do you distinguish pacemakers and ICDs on CXR?
ICD will have a thick wire, pacemaker wires are thin
Pacemakers often sit in the RA and RV
ICDs often sit in the LV
What 4 factors will make you concerned in a patient with arrhythmia?
New onset:
- Heart failure
- Myocardial ischaemia
- Shock
- Syncope
Describe the management of severe bradycardia (resus)
- Atropine 500mcg IV repeat to max 3mg (6 doses)
- Transcutaneous pacing
OR Isoprenaline 5mcg/min IV
OR adrenaline 2-10mcg/min IV - Transvenous pacing
Describe how transcutaneous pacing works
Using the defibrillator machine
Apply the pads as in defibrillation: R sternal edge, Apex
Adjust the machine to pacing, choose rate eg. 50-80
Check for electrical capture (on trace) and mechanical capture (pulse)
Define syncope and describe the types
Syncope is a transient loss of consciousness due to impaired cerebral perfusion.
- Vasovagal: most common. Assoc w emotions, prolonged standing, etc. Prodrome -> LOC -> recovery
- Cardiac: caused by structural or electrical problem that impairs blood flow eg. outflow obstruction, arrhythmia
- Orthostatic: caused by postural drop
Describe cardiac syncope
- Usually no prodrome eg. sudden
- Rapid recovery
- May have associated CP, SOB, palpitations
Describe the diagnostic process for syncope
- History
- Examination: cardio, neuro
- ECG
- Lying + standing BP
- Bloods: FBC, CRP, U+Es, glucose, TFTs, ?trop
- Consider: cardiac monitor, echo, CTH, etc
Describe the management of vasovagal syncope
Conservative:
- Trigger avoidance, education
- Hydration, rest
Medical:
- Fludrocortisone
- Midodrine (orthostatic)