lecture 6 - Tachy-arrhythmias

Question 1

what is a narrow complex tachycardia and give some examples

Answer 1

= 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)

Question 2

what is a broad complex tachycardia

Answer 2

= may be
• a supraventricular tachycardia with
aberrancy (i.e. bundle branch block)
• ventricular tachy-arrhythmia, e.g.
ventricular tachycardia (VT)

Question 3

Broad Complex Tachycardias -

Factors suggesting VT rather than SVT with aberrancy

Answer 3

• Extreme or indeterminate axis
• Very wide QRS
• Concordance across precordial leads

• Evidence of AV dissociation (diagnostic)
– dissociated P waves
– fusion beats
– capture beats

Question 4

what is a capture beat

Answer 4

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:

Question 5

what is a fusion beat

Answer 5

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.

Question 6

Tachy-arrhythmias

Clinical presentations

Answer 6

• 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

Question 7

Tachy-arrhythmias

Investigations

Answer 7

• 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

Question 8

Atrial Fibrillation

Epidemiology

Answer 8

• Commonest sustained arrhythmia

* Incidence increases with age:

Question 9

Atrial Fibrillation

Camm classification

Answer 9

• 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

Question 10

Atrial Fibrillation

Cardiac causes

Answer 10

• 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

Question 11

Atrial Fibrillation Non-cardiac causes

Answer 11

• Alcohol (binge or chronic
consumption)
• Thyrotoxicosis
• Sepsis, esp. chest sepsis
• Pulmonary embolism
• Chest trauma, including direct
trauma on cardiac catheterisation

Question 12

Atrial Fibrillation

Signs

Answer 12

• 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

Question 13

Atrial Fibrillation - Treatment of fast AF (acute)

Answer 13

• 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

Question 14

Atrial Fibrillation

Treatment of slow AF (acute)

Answer 14

• If pulseless®follow ALS algorithm (non-shockable rhythm)

• If pulse present ®follow brady-arrhythmia emergency guidelines (see
previous lecture)

Question 15

Atrial Fibrillation

Treatment (long term)

Answer 15

• 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

Question 16

Atrial Fibrillation

Rhythm control

Answer 16

• 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

Question 17

Atrial Fibrillation -Rate control

Answer 17

• 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

Question 18

Atrial Fibrillation

Thromboprophylaxis

Answer 18

• 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)

Question 19

Atrial Flutter • Wells classification:

management

Answer 19

• 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

Question 20

AT, AVNRT and AVRT

Definitions

Answer 20

• 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

Question 21

AT, AVNRT and AVRT

Treatment

Answer 21

• 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

Question 22

Ventricular Tachycardia

Epidemiology

Answer 22

• Common cause of sudden
cardiac death
• Often associated with
underlying structural heart
disease

Question 23

Ventricular Tachycardia Aetiologies

Answer 23

• 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

Question 24

Ventricular Tachycardia

Treatment (acute)

Answer 24

• 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

Question 25

Ventricular Tachycardia

Treatment (long term)

Answer 25

• Address underlying causes, e.g. treat coronary disease
• Continue chemoprophylaxis:
– first line is usually class II agent (e.g. bisoprolol) or class III agent (e.g.
amiodarone, sotalol)
– second line may include class I agent (e.g. flecainide, procainamide,
mexiletine) or more rarely class IV agent (e.g. verapamil)
• Consider VT ablation
• Consider implantable cardioverter defibrillator (ICD)

Question 26

• ICD lead in RV can deliver therapies if VT or VF is detected:

Answer 26

– for VT: anti-tachycardia pacing (ATP) followed by defibrillation (if ATP
fails)
– for VF: defibrillation

Question 27

ICD

Indications

Answer 27

• Secondary prevention
– for patients who have had failed sudden cardiac death (SCD), i.e.
ventricular fibrillation (VF) or haemodynamically significant ventricular
tachycardia (VT)
– in the absence of an easily correctable cause and a disqualifying
condition

• Primary prevention
– for patients at high risk of SCD
– many groups, e.g. familial conditions (long QT syndromes, Brugada
syndrome, ARVC), some congenital heart diseases, severe LVSD
– in the absence of a disqualifying condition

Question 28

ICD Complications

Answer 28

Procedural complications
3.36% *
Death 0.02%

Long term complications
3.4% per year **
Death 1% per year