Broad Complex Tachycardia

Question 1

Define broad complex tachycardia (BCT).

Answer 1

Rate > 100 bpm

QRS complexes > 120 ms.

This happens when the conduction does not go through the bundle of His and purkinje fibres, or if there is a block along the pathway.

Question 2

Explain the principles of management of BCT.

Answer 2

Identify the underlying rhythm and treat accordingly.

If there is doubt treat as ventricular tachycardia.

Giving AVN blocking agents to treat SVT with aberrancy when the patient is in VT can cause dangerous haemodynamic instability. This means that treating for VT when the patient is actually in SVT, has less potential for harm.

If WPW is suspected, avoid drugs that slow AV conduction.

Question 3

BCT with irregular rhythm.

Answer 3

If the lines are flat and wavy = ventricular fibrillation.

If the QRS is tall = AF with BBB, AF with aberrancy, AF pre-excited, Torsades de pointes, polymorphic VT.

Question 4

BCT with a regular rhythm.

Answer 4

VT

SVT with BBB

SVT with aberrancy

WPW with delta-waves.

Any cause of NCT along with a BBB or metabolic causes can result in a broad complex.

Question 5

It can be hard to differentiate VT from SVT with aberrancy.

How is it done?

Answer 5

Based on history - such as IHD favours VT.

12-lead ECG

Response to medication

Question 6

ECG findings in favour of VT.

Answer 6

+ve or -ve QRS concordance in all chest leads.

QRS > 160 ms

Marked left axis deviation or northwest axis. (QRS +ve in aVR)

AV dissociation or 2:1 or 3:1 Mobitz II Heart block

Fusion beats or capture beats.

RSR pattern where R is taller than R’.

Question 7

What are ventricular extrasystoles (ectopics)?

Answer 7

Common extra beats originating from the ventricles.

Can be symptomatic with a palpitations, thumping sensation or heart is missing a beat.

Pulse may feel irregular if there are frequent ectopics.

Question 8

Types of ventriclar ectopics.

Answer 8

Bigeminy - ectopic every other beat

Trigeminy - every third beat is ectopic

Couplet - two ectopics together

Triplet - three ectopics together

Question 9

What is this?

Answer 9

VF

Question 10

What is this?

Answer 10

VT

Question 11

What is this?

Answer 11

Torsades de pointes

Question 12

What is the star?

Answer 12

A fusion beat (*)—a ‘normal beat’ fuses with a vt complex creating an unusual complex.

Question 13

What is the star?

Answer 13

A capture beat (*)—a normal qrs amongst runs of vt. This would not be expected if the qrs breadth were down to bundle branch block or metabolic causes.

Question 14

What is this?

Answer 14

Bigeminy—a normal qrs is followed by a ventricular ectopic beat * then a compensatory pause, this pattern then repeats. The ectopic beats have the same morphology as each other so probably all share an origin.

Question 15

Definition of VT.

Answer 15

More than 3 ectopics together at a rate > 100 bpm.

Question 16

Management of BCT. Pt1.

Answer 16

1 - Check if there is a pulse.
No pulse -> Arrest protocol

2 - If there is pulse -> Give O2 if < 90%, IV access + 12-lead ECG

3 - Check if there adverse signs;
Shock (<90 SBP, > 100 bpm)
Chest pain/ischaemia on ECG
Heart failure
Syncope

Question 17

Management of BCT if patient has adverse signs.

Answer 17

1 - Get expert help.

2 - Sedate

3 - Up to 3 synchronised DC shocks. First 120-150J then 150-360J for subsequent shocks.

4 - Check and correct K+, Mg2+, Ca2+.

5 - Give amiodarone 300mg IV over 20 minutes or more.
Consider repeat shocks.
Give 900mg/24h IVI via central line

6 - Further cardioversion if needed

7 - If refractory seek expert help again and consider procainamide and overdrive pacing.

Question 18

Management of BCT if there are no adverse signs.

Answer 18

Correct electrolytes - K+, Mg2+, Ca2+.

Assess the rhythm if it is regular or irregular.

Question 19

Management of BCT if stable and regular rhythm.

Answer 19

If VT or uncertain rhythm give amiodarone 300 mg IV over 20 min or more.
Then 900 mg over 24h all via central line.

If there is known history of SVT and BBB treat as for NCT with adenosine.

Question 20

Management of BCT if stable and irregular rhythm.

Answer 20

Seek expert help.

Diagnosis is usually AF with BBB, pre-excited AF (amiodarone), or polymorphic VT like torsade de pointes (Give mg2+ 2g IVI)

If there is no success or becomes unstable sedate and synchronised DC shock.

Question 21

What should be done after correction of VT?

Answer 21

Establish cause.

Maintenance anti-arrhythmic therapy. if VT occurs after MI give IV amiodarone infusion for 12-24h.

If >24h after MI also start oral anti-arrhythmic sotalol (good LV) or amiodarone (poor LV).

ICD might be implanted to prevent further recurrence.

Question 22

Treatment of VF.

Answer 22

Use non-synchronised DC shock.

This is because there are no R waves to trigger defibrillation.

Question 23

Treatment of ectopics.

Answer 23

Usually not treated.

Giving anti-arrhythmics can cause a more dire outcome than not treating.

Question 24

What are torsade de pointes?

Answer 24

A form of VT with a constantly varying axis.

This is often seen in long QT syndromes.

It can be treated with high doses of b-blockers if along with long QT syndrome.
Usually treated with infusion of Mg2+ 2g

Torsades de pointes is a type of polymorphic (multiple shape) ventricular tachycardia. It translates from French as “twisting of the tips”, describing the ECG characteristics. It looks like normal ventricular tachycardia on an ECG however there is an appearance that the QRS complex is twisting around the baseline. The height of the QRS complexes progressively get smaller, then larger then smaller and so on. It occurs in patients with a prolonged QT interval.

Question 25

What is a rapid broad complex tachycardia shortly after a STEMI usually?

Answer 25

VT