Tachycardia

Question 1

What is the definition of tachycardia?

Answer 1

Cardiac arrhythmia with a rate >100 beats per minute (bpm)

Question 2

What are the 2 main types of tachycardia?

Answer 2

Narrow complex tachycardia and broad complex tachycardia

Question 3

What are the 2 types of narrow complex tachycardia?

Answer 3

Regular and irregular

Question 4

What are the different types of regular narrow complex tachycardia?

Answer 4

Regular (supraventricular tachycardia [SVT])

1. Sinus tachycardia
   - Physiological response to insult. Impulse originates from sino-atrial (SA) node.
2. Atrial tachycardia
   - Aberrant atrial focus producing impulse independent of SA node
3. Atrioventricular nodal re-entry tachycardia (AVNRT)
   Re-entry circuit within or near AV node
4. AV re-entry tachycardia (AVRT)
   - Re-entry circuit conducted from atria to ventricles via abnormal accessory pathway; usually due to Wolff-Parkinson-White (WPW) syndrome
5. Atrial flutter with regular AV block (eg 2:1, 3:1)
   Re-entry circuit within the atria

Question 5

What is irregular narrow complex tachycardia?

Answer 5

Irregular
Atrial fibrillation (AF)
- Atria twitch instead of beating in a coordinated manner

Question 6

Give examples of regular broad complex tachycardia?

Answer 6

Regular

Ventricular tachycardia (VT)
- Generated by a single ventricular focus

SVT with bundle branch block (BBB)
- This is rare. Any broad complex tachycardia should be treated as VT unless there the patient has an old ECG with clear previous bundle branch block of unchanged morphology.

Question 7

Give examples of irregular broad complex tachycardia?

Answer 7

Irregular

1. Polymorphic VT (Torsades de pointes)
   - Sinusoidal morphology usually due to abnormal ventricular repolarisation (long QT)
2. AF with bundle branch block

Question 8

What is the aetiology of tachycardia (pathological rather than physiological)?

Answer 8

Cardiac

• Post-cardiac arrest
• Post-myocardial infarction (MI)
• Long QT syndrome
• Valvular heart disease
• Cardiomyopathy

Non-cardiac

• Hypoxia
• Hypovolaemia
• Electrolyte abnormalities
• Especially hypo/hyper-kalaemia, -calcaemia or -magnesaemia
• Hypoglycaemia
• Hypo/hyperthermia
• Hypo/hyperthyroidism
• Sepsis

Drug-induced

• Cocaine
• Amphetamines
• Tricyclic antidepressants
• Beta blockers
• Digoxin
• Amiodarone

Question 9

What are the adverse clinical features of tachycardia?

Answer 9

Adverse features

Shock
- Hypotension, diaphoresis, pallor, increased capillary refill time (CRT)

Syncope
- Transient loss of consciousness

Myocardial ischaemia
- Ischaemic chest pain and/or ischaemic electrocardiogram (ECG) changes

Cardiac failure
- Orthopnoea, paroxysmal nocturnal dyspnoea (PND), bibasal crepitations, raised jugular venous pressure (JVP)

Question 10

What are the non adverse clinical features of tachycardia?

Answer 10

Non-adverse features

Palpitations
Dyspnoea
Anxiety

Question 11

What are the investigations of tachycardia?

Answer 11

Bloods

• Full blood count
• Urea & electrolytes
• Magnesium
• Bone profile (particularly noting calcium and phosphate)
• Thyroid function tests
• Other: liver function (useful pre-medication); coagulation (may need anticoagulation)

Chest radiograph (CXR)

Question 12

What are the further investigations of tachycardia?

Answer 12

Echocardiogram (echo)

Question 13

What is the initial management of tachycardia?

Answer 13

Assess patient from an ABCDE perspective

Maintain a patent airway
- Use manoeuvres, adjuncts, supraglottic or definitive airways as indicated

Controlled oxygen
- Maintain saturations (SpO2) 94-98%

Attach monitoring

• Pulse oximetry
• Non-invasive blood pressure
• Three-lead cardiac monitoring
• Defibrillator pads
• 12 lead ECG

Obtain intravenous (IV) access and take bloods

Give IV fluid challenge if appropriate and repeat as necessary

Identify and treat any reversible causes e.g. electrolyte abnormalities on initial VBG