lecture 6 - Tachy-arrhythmias Flashcards
what is a narrow complex tachycardia and give some examples
= any tachycardia originating above ventricles, e.g. • sinus tachycardia • atrial fibrillation • atrial flutter • atrial tachycardia * • junctional tachycardias (AVNRT and AVRT) *
- often just called supraventricular tachycardias (SVT)
what is a broad complex tachycardia
= may be • a supraventricular tachycardia with aberrancy (i.e. bundle branch block) • ventricular tachy-arrhythmia, e.g. ventricular tachycardia (VT)
Broad Complex Tachycardias -
Factors suggesting VT rather than SVT with aberrancy
- Extreme or indeterminate axis
- Very wide QRS
- Concordance across precordial leads
• Evidence of AV dissociation (diagnostic)
– dissociated P waves
– fusion beats
– capture beats
what is a capture beat
ECG waveform in VT is monomorphic. However, intermittently atrial breakthrough occurs before a ventricular beat has begun. This is referred to as a capture beat:
what is a fusion beat
A fusion beat occurs when a supraventricular and a ventricular impulse coincide to produce a hybrid complex.
It indicates that there are two foci of pacemaker cells firing simultaneously: a supraventricular pacemaker (e.g. the sinus node) and a competing ventricular pacemaker (source of ventricular ectopics).
The fusion beats are of intermediate width and morphology to the supraventricular and ventricular complexes.
Tachy-arrhythmias
Clinical presentations
• Asymptomatic • Palpitation (main symptom in most symptomatic cases) • Missed or extra heart beats • Dizziness • Syncope • Breathlessness • Chest pain • A complication, e.g. systemic embolism, heart failure or sudden cardiac death
Tachy-arrhythmias
Investigations
• Diagnosis is made by detecting the arrhythmia on ECG:
– 12-lead ECG
– continuous ambulatory ECG (Holter monitor) – e.g. 24-hour tape or 48-
hour tape or 7-day tape
– external loop recorder
– implantable loop recorder – e.g. REVEAL® device
• Other relevant investigations may include: – blood tests, including U&Es and TFTs – echocardiogram dictated by clinical scenario Atrial
Atrial Fibrillation
Epidemiology
- Commonest sustained arrhythmia
* Incidence increases with age:
Atrial Fibrillation
Camm classification
• Paroxysmal AF – self-terminating at least once
• Persistent AF – persists at least 48 hours without spontaneous
termination; can be converted to sinus rhythm with drugs or electricity
• Permanent AF – cannot be terminated with drugs or electricity
Atrial Fibrillation
Cardiac causes
• Coronary artery disease • Valvular heart disease, esp. MV disease • Cardiomyopathies and other causes of heart failure • Hypertension • Degenerative conduction tissue disease (sinoatrial node disease) • Myocarditis and pericarditis • Cardiac surgery
Atrial Fibrillation Non-cardiac causes
• Alcohol (binge or chronic consumption) • Thyrotoxicosis • Sepsis, esp. chest sepsis • Pulmonary embolism • Chest trauma, including direct trauma on cardiac catheterisation
Atrial Fibrillation
Signs
- Irregularly irregular pulse
- Variable pulse volume
- Single waveform JVP (subtle)
- Apical-to-radial pulse deficit (if fast AF)
- Variable intensity of first heart sound
- Signs of complications or of underlying cause
Atrial Fibrillation - Treatment of fast AF (acute)
• If pulseless®follow ALS algorithm (non-shockable rhythm)
• If pulse present but unstable ®synchronised DC cardioversion ASAP (to try
to achieve sinus rhythm) + drug (usually amiodarone or digoxin)
• If pulse present and stable ®several drug options e.g.
– beta blocker (usually first line)
– rate-limiting calcium channel blocker (alternative to beta blocker)
– flecainide (alternative to beta blocker)
– digoxin (if hypotensive or in heart failure)
– amiodarone (if hypotensive or in heart failure)
• Start anticoagulation (unless contraindicated) – usually bolus IV heparin
followed by low molecular weight heparin
• Treat precipitants, e.g. sepsis, electrolyte abnormalities, heart failure
Atrial Fibrillation
Treatment of slow AF (acute)
• If pulseless®follow ALS algorithm (non-shockable rhythm)
• If pulse present ®follow brady-arrhythmia emergency guidelines (see
previous lecture)
Atrial Fibrillation
Treatment (long term)
• Decide on rhythm control versus rate control:
– paroxysmal AF ®rhythm control (usually)
– persistent AF ®either rhythm or rate control (individualised decision)
– permanent AF ®rate control
- Choose means of thromboprophylaxis
- Treat precipitating or underlying causes, e.g. alcohol abstention
Atrial Fibrillation
Rhythm control
• Pharmacological cardioversion: – Class III agents, e.g. amiodarone, sotalol, ibutilide – Class I agents, e.g. flecainide, propafenone • Electrical cardioversion • Percutaneous AF ablation • Surgical AF ablation
rate vs rhythm control - Current evidence suggests there is no significant difference in morbidity and mortality between these two strategies ⇒strategy should be individualised and discussed with patient
Atrial Fibrillation -Rate control
• Pharmacological agents: – Class II agents (beta blockers, e.g. bisoprolol) – Class IV agents (calcium antagonists, e.g. diltiazem) – Digoxin • AV nodal ablation and permanent pacing (for fast AF) • Permanent pacing (for slow AF)
rate vs rhythm control - Current evidence suggests there is no significant difference in morbidity and mortality between these two strategies ⇒strategy should be individualised and
Atrial Fibrillation
Thromboprophylaxis
• Increased risk of left atrial appendage thrombus formation in AF due to blood stasis • Thrombo-prophylaxis should be considered in all patients according to CHA2DS2-VASc score • Target INR for warfarin in AF is 2.5 (range 2-3) • Newer oral anticoagulant drugs are now available, e.g. dabigatran, rivaroxaban and apixaban • Percutaneous or surgical left atrial appendage occlusion in selected patients (rarely done)
Atrial Flutter • Wells classification:
management
• Wells classification:
– type 1 (“typical” atrial flutter) – macro re-entrant tachycardia
involving low right atrial isthmus
– type 2 (“atypical” atrial flutter) – intra-atrial re-entrant tachycardia
• Causes are similar to those for atrial fibrillation
• Manage as per atrial fibrillation – typical atrial flutter amenable to flutter
ablation with relatively good success rate
AT, AVNRT and AVRT
Definitions
• AT = atrial tachycardia (or ectopic atrial tachycardia)
• AVNRT = atrioventricular nodal re-entry tachycardia
• AVRT = atrioventricular re-entry tachycardia
• AVNRT + AVRT = junctional tachycardias
• AT, AVNRT and AVRT often just referred to as supraventricular tachycardias
(SVT)
• AVNRT has a re-entry circuit within (or very close to) the AV node –
commonly with slow anterograde limb and fast retrograde limb
• AVRT has a re-entry circuit involving accessory pathways remote from the
AV node
AT, AVNRT and AVRT
Treatment
• Vagal manoeuvres
• Valsalva manoeuvres
• Carotid sinus massage
• Adenosine IV – may also help with diagnosis by temporarily slowing or
blocking anterograde AV nodal conduction
• If persistent, consider beta blockers, calcium antagonists or other drugs
• In longer term, radiofrequency ablation usually effective
Ventricular Tachycardia
Epidemiology
• Common cause of sudden cardiac death • Often associated with underlying structural heart disease
Ventricular Tachycardia Aetiologies
• Ischaemia • Myocardial disease, e.g. – scar from ischaemic heart disease – cardiomyopathies, e.g. HCM, DCM, ARVC – cardiac infiltration, e.g. sarcoidosis • Idiopathic (often arising from RVOT) • Long QT syndromes – associated with torsades de pointes
Ventricular Tachycardia
Treatment (acute)
• If pulseless®follow ALS algorithm and deliver defibrillation ASAP
(shockable rhythm)
• If pulse present but unstable ®synchronised DC cardioversion ASAP
• If pulse present and stable ®
– several drug options e.g. amiodarone (usually safe first line), lidocaine
and beta blocker
– overdrive pacing
– still requires urgent treatment
• Address underlying/precipitating causes, e.g. electrolyte abnormalities and
ischaemia
