Arrhythmias Flashcards
1st degree heart block
PR > 200ms (5ss)
‘Marked’ > 300ms
Delay without interruption from atria –> ventricles
Causes:
- increased vagal tone, athletic
- inferior MI
- myocarditis (Lyme)
- HyperK
- BB, CCB, digoxin, Amiodarone
- normal variant
No treatment needed
2nd degree heart block - Mobitz type 1
Wenckebach phenomenon
Reversible conduction block at AV node. Progressive fatigue of AV nodal cells
ECG:
- Progressive lengthening of PR followed by absence of QRS
- P-P interval fairly constant
Causes:
- BB, CCB, digoxin, amiodarone
- increased vagal tone, athletes
- inferior MI.
- myocarditis
- following MV/TOF repair
Asymptomatic: no treatment
Symptomatic: atropine
2nd degree heart block - Mobitz type 2
Failure of HIs-Purkinje system below the AV node - structural damage
ECG:
- PR constant
- RR interval surrounding dropped beats is an exact multiple of preceding RR interval
- often preceding LBBB or bifasiccular block
-75% block is distal to BoH - broad QRS
- 25% block is within BoH - narrow QRS
- may be no pattern to dropped beats or a fixed relationship eg. 2:1, 3:1
Causes:
- Anterior MI - septal infarction, necrosis of bundle branches
- Lenegre’Lev disease
- MV repair
- Rheumatic fever, myocarditis, Lyme disease
- AI: SLE, systemic sclerosis
- Infiltrative: amyloidosis, haemochromatosis, sarcoidosis
- HyperK
- BB, CCB, digoxin, amiodarone
Management:
- More likely for severe bradycardia and 3rd degree HB
- risk of systole 35%/year
- immediate admission for cardiac monitoring & pacemaker
2nd degree HB with fixed ratio blocks 2:1, 3:1 or 4:1 conduction
2:1 - one normal cycle, then one with an absent QRS.
3:1 - two normal cycles, then one with an absent QRS
Mobitz I: narrow QRS (block at level of AV node)- improves with atropine
Mobitz 2: broad QRS (usually in context of LBBB/BFB) - worsens with atropine
Third degree/complete heart block
Atrial conduction is normal, but no beats are conducted to ventricles via AV node. Ventricles are excited by their own internal ectopic pacemaker (junctional or ventricular escape rhythm)
Symptoms:
- Syncope
- HF
- Regular bradycardia 30-50bpm
- Wide pulse pressure
- JVP - cannon waves
- Variable intensity of S1
ECG:
- P wave 90/min (more P’s than QRS’)
- QRS 36/min, 160ms (4 ss)
- variable PR
- no relationship between P and QRS, but both are present
- RAD
- escape rhythms present
Causes:
- Inferior MI (may be transient)
- AV-nodal blocking drugs - CCB, BB, digoxin
- Bundle of His fibrosis or BBB of both branches - Lev’s/Lenegre’s disease
Management: urgent pacemaker
Bundle branch block
Time taken for depolarisation to spread through ventricles is prolonged due to the block
ECG:
- QRS > 120
- normal PR
RBBB
Delayed activation of RV
ECG:
- QRS > 120
- V1-3 RSR (M)
- I, aVL, V5-6 (lateral) W shaped QRS
- appropriate discordance - ST depression/T wave inversion V1-3
Causes:
- ASD
- RVH
- IHD
- Rheumatic heart disease
- myocarditis
- cardiomyopathy
Management: no treatment needed
LBBB
Septum usually activated L –> R, in LBBB septal activation reversed
ECG:
- QRS > 120
- Dominant S (QS or rS complex) in V1 (W)
- Prolonged R wave in V5-6 (M)
- No Q waves in lateral leads
- should be discordant changes in ST and T wave (opposite from usual)
- LAD
Causes: I
- if new onset consider anterior MI (STEMI-equivalent), especially if concordant ST changes
- aortic stenosis
- HTN
- dilated cardiomyopathy
- HyperK
- digoxin
Management: thombolysis if ACS, no other treatment needed.
Bifascicular block
2 of the 3 main fascicles of the His/Purkinje system are blocked:
- R fascicle
- L anterior fascicle (single coronary artery blood supply, LAD, therefore most commonly blocked)
- L posterior fascicle (dual blood supply, R + L circumflex arteries)
ECG:
- RBBB + LAFB (LA hemiblock) - LAD
- RBBB + LPFB (LP hemiblock) - RAD
- LAFB + LPFB = LBBB
Causes:
-50-80% structural heart disease
- 40-60% ischaemic heart disease
- aortic stenosis
- anterior MI
- hyperK
Management:
- New bifascular block in patient with acute MI needs emergency pacemaker
- bifasciular block + syncope/presyncope -admission and monitoring
- RBBB and LAH - can be stable
- RBBB + LPH - emergency pacemaker
Incomplete RBBB
RSR’ pattern in V1-V3 with QRS < 120
Normal variant, common in children
No clinical significance
Left anterior fascicular block
ECG:
- LAD
- qR complexes in I, aVL
- rS complexes in II, III, aVF
- prolonged R wave peak time in aVL > 45
Left axis deviation
II, III and avF are negative
I and avL are positive
Left posterior fascicular block
ECG:
- RAD
- rS in I and aVL
- qR in II, III, aVF
- prolonged R wave peaks time in aVF
To make diagnosis need to exclude other causes of RAD - no evidence of RVH, PE, tricyclic OD, lateral STEMI
Right axis deviation
II, III, aVF are positive.
I, aVL are negative
Sinus arrythmia
ECG:
- sinus rhythm
- variation in P-P interval (>120ms) with respiration –> irregular ventricular rate
- constant PR interval
- HR increases on inspiration
Premature atrial complexes/atrial extrasystole /ectopic
ECG:
- Absent or abnormal P wave
- early QRS of similar morphology to normal sinus beats
- PR interval relatively short, but still > 120ms (<120ms = PJC)
- SA node rests - post-extrasystolic pause
- blocked PAC - not followed by QRS
When ectopics alternate with normal QRS:
- Bigeminy: every other beat is a PAC
- Trigeminy: every 3rd beat is a PAC
Couplet: 2 consecutive PACs
Triplet: 3 consecutive PACs
Symptoms: heart skipping a beat
Causes:
- anxiety
- sympathomimetics
- B-agonists, digoxin
- caffeine
- HypoK/Mg
- ischaemia
Premature ventricular complexes/ extrasystloes/ectopics
ECG:
- early broad QRS > 120ms with abnormal morphology
- no preceding P-wave - inverted P wave after
- discordant ST and T wave changes
- followed by compensatory pause - interval equals double the preceding R-R interval
When ectopics alternate with normal QRS: - - bigemeny: every other bead
- trigemency: every 3rd beat
Couplet: 2 in a row
Symptoms: heart skipping a beat
Same causes as PACs
Premature Junctional Complexes
Arising from ectopic focus in AV junction
ECG:
- narrow QRS, sooner than expected
- either without preceding P-wave or with an inverted P wave (II, III, aVF) which may appear before (PR < 120ms)/during/after QRS
- compensatory pause
- If PJCs arrive early may have RBBB morphology
Junctional escape rhythm
ECG:
- HR 40-60bpm
- QRS < 120ms
- no relationship between QRS and preceding atrial activity (P wave/fliutter wave/fibrillatory wave
Causes:
- hyperK
- Complete HB
- BBB, CCB, digoxin
Ventricular escape rhythm
ECG:
- HR 20-40bpm
- QRS > 120ms +/- BBB morphology
Supraventricular tachycardias
Regular atrial:
- sinus tachycardia
- atrial tachycardia
- atrial flutter.
Irregular atrial:
- atrial fibrillation
- atrial flutter with variable block
- multifocal atrial tachycardia
Regular atrioventricular:
AV Nodal re-entry tachycardia (AVRNT)
AV nodal re-entry tachycardia (AVNRT)
Commonest cause of palpitations in patients with structurally normal hearts
ECG:
- regular tachycardia 140-280bpm
- QRS < 120ms
- inverse P waves II, III, aVF - can be within or after QRS
- rate related ST depression
Spontaneous or provoked by:
- exertion
- caffeine, alcohol
- B agonists (salbutamol) or sympathomimetics (amphetamines)
Symptoms:
- paroxysmal
- sudden onset rapid regular palpitations 140-280bpm
- presyncope/syncope
- SOB
- anxiety
May self-resolve or need treatment:
- vagus stimulation
- adenosine
- CCB, BB, amiodarone
HOCM
Number 1 cause of sudden death in young people
Asymmetrical thickening of inter-ventricular septum –> obstruction of LV outflow tract –> exertional syncope
ECG: 5% have normal ECG, consider Echo if suspicious
- LVH with non-specific ST and T wave abnormalities
- Deep, narrow dagger Q waves in lateral (I, aVL, V5-6) and inferior (II, III, aVF)
Management:
- symptomatic - immediate admission
- asymptomatic - refer
WPW
Congenital accessory pathway between atria and ventricles - can conduct towards and away from ventricle
ECG:
- PR < 120ms
- Delta wave: slurring slow rise of initial part of QRS
- QRS > 110ms
- ST and T wave discordant changes (opposite direction to major component of QRS)
- can cause paroxysmal tachycardia
Treatment: ablation
Pericardial effusion/tamponade
ECG:
- electrical alternans: alternating short and tall QRS
- sinus tachycardia = cardiac tamponade
Arrhthmogenic Right Ventricular Dysplasia (ARVD)
AD genetic disorder - fatty infiltration of R ventricular free wall, predisposing to ventricular arrhythmia, sudden death, biventricular failure
2nd most common cause of sudden cardiac death in young people after HOCM
ECG:
- RVH: RAD + dominant wave in V1
- RV strain: concurrent T wave inversion in inferior and precordial (v1-3) leads
- QRS widening V1-3
- Epsilon waves: small blip following each QRS best seen in V1 and inferior leads
Symptoms:
- palpitations, syncope or cardiac arrest precipitated by exercise
Hyperkalaemia
- peaked, tented T waves
- P wave widening/flattening
- PR prolongation
- bradyarrythmia: sinus Brady, AV block, slow AF
- BBB/FB.
- QRS widening with bizarre morphology
Brugada syndrome
Arrythmogenic sodium channelopathy - mutation in cardiac Na gene
More common in SE Asian males, presentation at 40y
ECG: changes in at least 2 of R precordial leads (V1-3)
- Type 1: coved ST elevation > 2mm at J point, followed by inverted T wave
- Type 2: saddleback ST segments with > 2mm J point elevation, > 1mm STE + positive or biphasic T wave
- Type 3: coved or saddleback STE < 1mm.
Symptoms:
- ventricular arrhythmias: paroxysmal syncope, seizure-like events, nocturnal agonal respirations
- sudden death
- asymptomatic
Criteria:
1) Diagnostic Type 1 ECG pattern
2) +
- Positive FH - sudden death < 45y, type 1 ECG
- Arrhythmia related symptoms
- Documented ventricular arrhythmias
Treatment: if symptomatic admit for implantable cardiverter-defibrillator (ICD)
Atrial flutter
Re-entry circuit in RA
ECG:
- P-wave rate 300bpm - QRS rate 75 (4:1), 100 (3:1) or 150bpm (2:1) depending on block
- Narrow QRS
- no flat lines between P waves - saw tooth
- AV node cannot pass on rhythms > 150, therefore associated block eg 2:1
Ventricular tachycardia
ECG:
- > 160bpm
- no obvious P waves
- Broad QRS
Supraventricular tachycardia
ECG:
- 140 - 280bom
- P waves usually not identifiable
- Regular narrow QRS (unless also BBB)
Management:
1) Valsalva manoeuvre: lying face up, blows into syringe for 15s
2) Carotid sinus massage - record ECG during procedure and have defibrillator ready incase of VT
Long QT
ECG:
- QT > 450 may lead to VT
LVH
ECG:
- R wave in V6 > 25mm
- R wave in V6 + S wave in V1 > 25mm
- invested T wave in aVL, V5-V6
- Axis normal or LAD
RVH
ECG:
- Tall R wave in V1
- T wave inversion in V1-V3 or V4
- Deep S wave in V6
- RAD
Previous MI
ECG:
- pathological Q waves
- inversion T waves
- loss of R wave progression across chest leads following an anterior MI
- LBBB following previous MI
When to admit patients with current palpitations
1) VT
2) Persistent SVT
3) Haemodynamic instability
4) High risk structural hear disease including IHD
5) Features suggestive of serious underlying cause:
- High degree AV block
- significant SOB/chest pain/syncope/near syncope
- FH sudden cardiac death < 40y
- precipitated by exercise
When to refer patients who do not require admission but have current palpitations
1) Atrial flutter
2) SVT terminated by Valsalva or carotid massage
3) Pre-excitation/WPW
4) Ventricular ectopics where underlying heart disease suspected or extrasystoles or frequency or VT suspected
Investigations for palpitations
1) ECG
2) Bloods: FBC, U&E, LFT, TFT, HbA1c
Driving advice for palpitations
G1: if has caused or likely to cause incapacity then stop and restart when underlying cause identified and well controlled for 4 weeks
G2: stop of has caused or likely to cause incapacity and restart when underlying cause identified and arrhythmia controlled for 3 months.
If working at height our with dangerous machinery will need to stop until a diagnosis is confirmed/treated
When to refer for urgent cardiology assessment if history of palpitations
1) history of syncope/near syncope
2) Palpitations precipitated by exercise
3) FH sudden death < 40y
4) 2nd or 3rd degree AV block on ECG
When to refer routinely to cardiology if history of palpitations
1) Accompanying lightheadedness/ chest pain
2) History of symptoms of structural heart disease (arrange Echo) , heart failure of HTN
3) Resting ECG abnormality that isn’t 2nd or 3rd degree HB
4) History of recurrent sustained tachycardia, AF or flutter.
5) History of symptoms consistent with paroxysmal SVT (sudden onset and offset of a fast regular heartbeat, with multiple uneventful rhythm monitor recordings)
6) Ventricular ectopics if underling heart disease suspected or they are frequent or VT suspected.
When not to referral is not indicated for palpitations
1) Not provoked by exercise
2) Not associated with lightheadedness, syncope, persistent SOB or chest pain
3) Not associated with signs of ECG features of structural heart disease, HF or HTN
4) Not associated with FH sudden cardiac death
When to arrange holder monitoring for palpitations
1) < 1/week and:
- last for > 1h - attend ED during next episode & provide letter asking for immediate ECG
- short lived - self-activated event recorder
2) Daily - 24h/48h holter
Long QT:
syndrome and causes
Inherited delayed repolarization of ventricles
Can lead to VT/TdP –> sudden collapse/death
A normally corrected QT is < 430 in males and 450 in femailes
Causes:
- congenital: Jervell-Lange-Nielsen syndrome (deafness) or Romano-Ward syndrome (no deafness)
- amiodarone, sotalol, class 1a antiarrythmic drugs
- TCAs, SSRIs, esp citalopram
- methadone
- chloroquine
- terfenadine
- erythromycin
- haloperidol
- ondansetron
- hypoCa, hypoK, hypoMg
- ACS
- myocarditis
- Hypotheramia
- SAH
