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Brugada Algorithm (VT vs. Aberrant SVT)

Brugada algorithm (ventricular tachycardia vs. SVT with aberrant conduction)

Wide-Complex Tachycardia
Brugada Algorithm (VT vs. Aberrant SVT)
Brugada Algorithm in Clinical Practice
Brugada Algorithm - Limitations

Wide-Complex Tachycardia

Wide-complex tachycardia is defined as:

Tachycardia (frequency > 100/min.)
With wide QRS complexes (≥ 0.12s)

The differential diagnosis of wide QRS complex tachycardia

Wide-Complex Tachycardia Has 3 Main Causes

Wide-complex tachycardia has 3 main causes

Ventricular tachycardia (accounts for 80% of wide-complex tachycardias)
Supraventricular tachycardia with aberrant conduction
Supraventricular tachycardia with accessory pathway (Antidromic AVRT)

Rare causes of wide-complex tachycardia:

Severe electrolyte imbalance (hyperkalemia)
Intoxication with sodium channel blockers
Pacemaker tachycardia

For differential diagnosis of the mechanism of wide-complex tachycardia, diagnostic algorithms are used

10% of wide-complex tachycardias (WCT) cannot be clearly specified

Diagnosis of the mechanism is important for treatment

WCT is an urgent condition, often life-threatening, and requires urgent emergency treatment

For wide-complex tachycardia:

80% is ventricular tachycardia
If the patient is older than 50 years, then 90% is ventricular tachycardia

The principle is, unclear wide-complex tachycardia is always treated as ventricular tachycardia

Brugada Algorithm (VT vs. Aberrant SVT)

It is the most commonly used algorithm for differentiating the mechanism of wide-complex tachycardia
Differentiates ventricular tachycardia from Aberrant Supraventricular Tachycardia (SVT)

Does not differentiate Preexcitation SVT (Antidromic AVRT)

Brugada Algorithm has 3 pitfalls

Cannot differentiate Idiopathic Ventricular Tachycardia
Preexcitation SVT (Antidromic AVRT)

May incorrectly classify as ventricular tachycardia

Branch Reentry Ventricular Tachycardia

May incorrectly classify as Aberrant SVT

Wide-Complex Tachycardia

Brugada Algorithm differentiates the mechanism of wide-complex tachycardia
Differentiates ventricular tachycardia from Aberrant Supraventricular Tachycardia (SVT)

Does not differentiate Preexcitation SVT (Antidromic AVRT)

Brugada Algorithm in Clinical Practice

Sensitivity: 98% Specificity: 96%
Brugada Algorithm has 2 parts
Ventricular Tachycardia (VT) is usually easily and quickly diagnosed in the 1st part

Using 4 ECG criteria

The problem arises if wide-complex tachycardia (WCT) presents with a bundle branch block pattern (LBBB, RBBB)

WCT does not meet the first 4 ECG criteria

WCT is then assessed according to the 2nd part of the algorithm

Brugada algorithm, ECG criteria, diagnosis of wide QRS complex tachycardias, absence RS complex, RS interval, AV dissociation, Morphology (V1,V6) - RBBB and LBBB

Brugada Algorithm (Part 1)

1. Is there an RS complex in the precordial leads
2. RS interval > 100ms
3. AV dissociation
4. If the first 3 conditions are not met

Then assess EKG morphology of WCT (whether it resembles RBBB or LBBB)
Proceed to Part 2 of the Brugada Algorithm

It could be ventricular tachycardia or aberrant SVT

Brugada algorithm, morphology criteria in precoridal leads V1, V6, LBBB shaped VT, RBBB shaped VT

Brugada Algorithm (Part 2)

Evaluate EKG morphology in leads (V1 and V6)
If the morphology in (V1, V6) is characteristic of RBBB or LBBB

Then it is likely Aberrant SVT

If the morphology in (V1, V6) does not resemble RBBB or LBBB

Then it is likely ventricular tachycardia
Normal cardiac axis (+90° to -30°)

However, this is against VT

WCT with morphology of Tawara block

Sometimes it cannot be differentiated

Brugada Algorithm - Limitations

Cannot differentiate idiopathic ventricular tachycardia:

Ventricular tachycardias from the outflow tract

Have an ectopic focus in the outflow tracts
The resulting ventricular vector directs towards lead II (i.e., normal cardiac axis)

This is rare for VT

Fascicular VT

Has reentry in the area of a single fascicle of the left Tawara branch

Results in an EKG pattern of SVT with RBBB

Preexcitation SVT (Antidromic AVRT) is falsely classified as ventricular tachycardia

Because the ventricles are depolarized via an accessory pathway from the base
The resulting ventricular vector directs towards lead II (i.e., normal cardiac axis)

This is rare for VT

Reentry ventricular tachycardia is falsely classified as aberrant SVT

Reentry occurs through both Tawara branches or through both fascicles

Results in an EKG pattern of SVT with Tawara block

There are 2 VTs with narrow QRS complexes (≤ 0.12s), which is a paradox:

VT from the ventricular septum
Fascicular VT
These 2 VTs are then evaluated as supraventricular tachycardia (which is a mistake)

ECG Brugada algorithm, RS complex in all precordial leads (NO) - Ventricular tachycardia

Wide-Complex Tachycardia

QRS Width: 0.2s
Heart Rate 160/min.
Brugada Algorithm

Condition 1: Is there an RS complex in precordial leads (No)
Precordial leads show only a deep S wave (negative precordial concordance)
This indicates ventricular tachycardia

Posterior fascicular ventricular tachycardia

ECG Brugada algorithm, AV dissociation, Fusion beat, Capture beat, Narrow complex fasciculer ventricular tachycardia

Narrow-Complex Tachycardia

QRS Width: 0.12s (QRS complexes are borderline widened)

Even though this is VT

Heart Rate 100/min.
Brugada Algorithm

Condition 3: Is there an AV dissociation, merged, captured beat (Yes)

On the ECG, we see key signs of ventricular tachycardia

AV dissociation

P waves (arrows) are independent of QRS complexes

Merged beat (6th QRS complex in continuous lead II)
Captured beat (7th QRS complex in continuous lead II)

This is Fascicular VT (re-entry is in the left posterior fascicle)

Pattern of Right Tawar's Bundle Block

Dominant R (V1)
Deep and wide S (V6)

Left Anterior Hemiblock

Negative QRS (II, aVF)
Positive QRS (I)

ECG Brugada algorithm, RBBB morphology, extreme right axis deviation, Fascicular ventricular tachycardia, re-entry - left posterior fasciculus

Wide-Complex Tachycardia

QRS Width: 0.13s
Heart Rate 143/min.
Pattern of Right Bundle Branch Block

rsR´ (V1)
Deep and wide S (V6)

Brugada Algorithm (Part 2)

Presence of Right Bundle Branch Block Pattern (RBBB)

However, the cardiac axis is extremely deviated to the right

This rules out SVT with RBBB

This is Fascicular VT (re-entry in the left posterior fascicle)

Pattern of Right Bundle Branch Block
Pattern of Extreme Right Axis Deviation

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 166/min.
QRS Alternans

Amplitude of QRS complexes regularly changes

Brugada Algorithm

Condition 2: RS Interval > 100ms (Yes)

It is Ventricular Tachycardia

AVNRT, SVT with aberrant conduction - RBBB

ECG Brugada algorithm, RBBB morphology, normal heart axis, SVT (AVNRT) with aberrant conduction due to bundle branch block

Wide Complex Tachycardia

QRS Duration 0.14s
Heart Rate 212/min.
Brugada Algorithm (Part 2)

Typical Pattern RBBB (right bunny ear is larger)
Heart Axis is normal (Dominant R in lead II)

It is SVT with RBBB

Specifically, AVNRT with RBBB

Antidromic AVRT, SVT with aberrant conduction due to the Wolff-Parkinson-White (WPW) syndrome

Wide Complex Tachycardia

QRS Duration 0.2s
Heart Rate 200/min.
The patient has WPW Syndrome

On the ECG, during sinus rhythm, had a delta wave

Brugada Algorithm (Part 2)

Atypical Pattern RBBB
Heart Axis is deviated to the right

According to the Brugada Algorithm, this is a ventricular tachycardia

However, the patient has Antidromic AVRT (preexcitation SVT)
The Brugada Algorithm falsely identifies preexcitation SVT as VT

Sometimes a modified Brugada Algorithm is used

ECG ventricular tachycardia RBBB morphology, Brugada algorithm No RS copmlex in precordial lead

Wide Complex Tachycardia

QRS Duration 0.2s
Heart Rate 165/min.
Brugada Algorithm

Condition 1: Is the RS Complex in the precordial leads (No)
In the precordial leads, there is only a deep S wave (negative precordial concordance)
It is ventricular tachycardia with a RBBB pattern

LBBB, aberrant supraventricular tachycardia

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 165/min.
Brugada Algorithm (Part 2)

Typical Pattern LBBB
Heart Axis is deviated to the left upper quadrant

This is a normal LBBB pattern

It is most likely SVT with LBBB

Ventricular Tachycardia is less likely

Wide Complex Tachycardia

QRS Duration 0.14s
Heart Rate 158/min.
Brugada Algorithm (Part 2)

Typical Pattern RBBB
Heart Axis is deviated to the right lower quadrant

Which can occur with RBBB

It is most likely SVT with RBBB

Ventricular Tachycardia is less likely

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 214/min.
Brugada Algorithm

Condition 3: Presence of AV Dissociation (Yes)

P waves (arrows) are independent of QRS complexes

It is Ventricular Tachycardia

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 150/min.
Brugada Algorithm

Condition 1: Is the RS Complex in the precordial leads (No)

It is Ventricular Tachycardia

Which is also confirmed by AV Dissociation (arrows)

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers

Home /

Brugada Algorithm (VT vs. Aberrant SVT)

Brugada algorithm (ventricular tachycardia vs. SVT with aberrant conduction)

Wide-Complex Tachycardia
Brugada Algorithm (VT vs. Aberrant SVT)
Brugada Algorithm in Clinical Practice
Brugada Algorithm - Limitations

Wide-Complex Tachycardia

Wide-complex tachycardia is defined as:

Tachycardia (frequency > 100/min.)
With wide QRS complexes (≥ 0.12s)

Wide complex tachycardia, ventricular tachycardia, Brugada algorithm

Wide complex tachycardia, SVT with aberrant conduction due to bundle branch block, RBBB, LBBB, Brugada algorithm

Wide complex tachycardia, Orthodrome AV, SVT with aberrant conduction due to the Wolff-Parkinson-White (WPW) syndrome, Brugada algorithm

Brugada algorithm, Differential Diagnosis of Wide-Complex Tachycardia

Wide-Complex Tachycardia Has 3 Main Causes

Wide-complex tachycardia has 3 main causes

Ventricular tachycardia (accounts for 80% of wide-complex tachycardias)
Supraventricular tachycardia with aberrant conduction
Supraventricular tachycardia with accessory pathway (Antidromic AVRT)

Rare causes of wide-complex tachycardia:

Severe electrolyte imbalance (hyperkalemia)
Intoxication with sodium channel blockers
Pacemaker tachycardia

For differential diagnosis of the mechanism of wide-complex tachycardia, diagnostic algorithms are used

10% of wide-complex tachycardias (WCT) cannot be clearly specified

Diagnosis of the mechanism is important for treatment

WCT is an urgent condition, often life-threatening, and requires urgent emergency treatment

For wide-complex tachycardia:

80% is ventricular tachycardia
If the patient is older than 50 years, then 90% is ventricular tachycardia

The principle is, unclear wide-complex tachycardia is always treated as ventricular tachycardia

Brugada Algorithm (VT vs. Aberrant SVT)

It is the most commonly used algorithm for differentiating the mechanism of wide-complex tachycardia
Differentiates ventricular tachycardia from Aberrant Supraventricular Tachycardia (SVT)

Does not differentiate Preexcitation SVT (Antidromic AVRT)

Brugada Algorithm has 3 pitfalls

Cannot differentiate Idiopathic Ventricular Tachycardia
Preexcitation SVT (Antidromic AVRT)

May incorrectly classify as ventricular tachycardia

Branch Reentry Ventricular Tachycardia

May incorrectly classify as Aberrant SVT

Wide complex tachycardia, SVT with aberrant conduction due to bundle branch block, RBBB, LBBB

Wide complex tachycardia, Orthodrome AV, SVT with aberrant conduction due to the Wolff-Parkinson-White (WPW) syndrome

Wide-Complex Tachycardia

Brugada Algorithm differentiates the mechanism of wide-complex tachycardia
Differentiates ventricular tachycardia from Aberrant Supraventricular Tachycardia (SVT)

Does not differentiate Preexcitation SVT (Antidromic AVRT)

Brugada Algorithm in Clinical Practice

Sensitivity: 98% Specificity: 96%
Brugada Algorithm has 2 parts
Ventricular Tachycardia (VT) is usually easily and quickly diagnosed in the 1st part

Using 4 ECG criteria

The problem arises if wide-complex tachycardia (WCT) presents with a bundle branch block pattern (LBBB, RBBB)

WCT does not meet the first 4 ECG criteria

WCT is then assessed according to the 2nd part of the algorithm

Brugada Algorithm (Part 1)

1. Is there an RS complex in the precordial leads
2. RS interval > 100ms
3. AV dissociation
4. If the first 3 conditions are not met

Then assess EKG morphology of WCT (whether it resembles RBBB or LBBB)
Proceed to Part 2 of the Brugada Algorithm

It could be ventricular tachycardia or aberrant SVT

Brugada Algorithm (Part 2)

Evaluate EKG morphology in leads (V1 and V6)
If the morphology in (V1, V6) is characteristic
of RBBB or LBBB

Then it is likely Aberrant SVT

If the morphology in (V1, V6) does not resemble
RBBB or LBBB

Then it is likely ventricular tachycardia
Normal cardiac axis (+90° to -30°)

However, this is against VT

WCT with morphology of Tawara block

Sometimes it cannot be differentiated

Brugada Algorithm - Limitations

Cannot differentiate idiopathic ventricular tachycardia:

Ventricular tachycardias from the outflow tract

Have an ectopic focus in the outflow tracts
The resulting ventricular vector directs towards lead II (i.e., normal cardiac axis)

This is rare for VT

Fascicular VT

Has reentry in the area of a single fascicle of the left Tawara branch

Results in an EKG pattern of SVT with RBBB

Preexcitation SVT (Antidromic AVRT) is falsely classified as ventricular tachycardia

Because the ventricles are depolarized via an accessory pathway from the base
The resulting ventricular vector directs towards lead II (i.e., normal cardiac axis)

This is rare for VT

Reentry ventricular tachycardia is falsely classified as aberrant SVT

Reentry occurs through both Tawara branches or through both fascicles

Results in an EKG pattern of SVT with Tawara block

There are 2 VTs with narrow QRS complexes (≤ 0.12s), which is a paradox:

VT from the ventricular septum
Fascicular VT
These 2 VTs are then evaluated as supraventricular tachycardia (which is a mistake)

Wide-Complex Tachycardia

QRS Width: 0.2s
Heart Rate 160/min.
Brugada Algorithm

Condition 1: Is there an RS complex in precordial leads (No)
Precordial leads show only a deep S wave (negative precordial concordance)
This indicates ventricular tachycardia

Narrow-Complex Tachycardia

QRS Width: 0.12s (QRS complexes are borderline widened)

Even though this is VT

Heart Rate 100/min.
Brugada Algorithm

Condition 3: Is there an AV dissociation, merged, captured beat (Yes)

On the ECG, we see key signs of ventricular tachycardia

AV dissociation

P waves (arrows) are independent of QRS complexes

Merged beat (6th QRS complex in continuous lead II)
Captured beat (7th QRS complex in continuous lead II)

This is Fascicular VT (re-entry is in the left posterior fascicle)

Pattern of Right Tawar's Bundle Block

Dominant R (V1)
Deep and wide S (V6)

Left Anterior Hemiblock

Negative QRS (II, aVF)
Positive QRS (I)

Wide-Complex Tachycardia

QRS Width: 0.13s
Heart Rate 143/min.
Pattern of Right Bundle Branch Block

rsR´ (V1)
Deep and wide S (V6)

Brugada Algorithm (Part 2)

Presence of Right Bundle Branch Block Pattern (RBBB)

However, the cardiac axis is extremely deviated to the right

This rules out SVT with RBBB

This is Fascicular VT (re-entry in the left posterior fascicle)

Pattern of Right Bundle Branch Block
Pattern of Extreme Right Axis Deviation

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 166/min.
QRS Alternans

Amplitude of QRS complexes regularly changes

Brugada Algorithm

Condition 2: RS Interval > 100ms (Yes)

It is Ventricular Tachycardia

Wide Complex Tachycardia

QRS Duration 0.14s
Heart Rate 212/min.
Brugada Algorithm (Part 2)

Typical Pattern RBBB (right bunny ear is larger)
Heart Axis is normal (Dominant R in lead II)

It is SVT with RBBB

Specifically, AVNRT with RBBB

Wide Complex Tachycardia

QRS Duration 0.2s
Heart Rate 200/min.
The patient has WPW Syndrome

On the ECG, during sinus rhythm, had a delta wave

Brugada Algorithm (Part 2)

Atypical Pattern RBBB
Heart Axis is deviated to the right

According to the Brugada Algorithm, this is a ventricular tachycardia

However, the patient has Antidromic AVRT (preexcitation SVT)
The Brugada Algorithm falsely identifies preexcitation SVT as VT

Sometimes a modified Brugada Algorithm is used

Wide Complex Tachycardia

QRS Duration 0.2s
Heart Rate 165/min.
Brugada Algorithm

Condition 1: Is the RS Complex in the precordial leads (No)
In the precordial leads, there is only a deep S wave (negative precordial concordance)
It is ventricular tachycardia with a RBBB pattern

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 165/min.
Brugada Algorithm (Part 2)

Typical Pattern LBBB
Heart Axis is deviated to the left upper quadrant

This is a normal LBBB pattern

It is most likely SVT with LBBB

Ventricular Tachycardia is less likely

Wide Complex Tachycardia

QRS Duration 0.14s
Heart Rate 158/min.
Brugada Algorithm (Part 2)

Typical Pattern RBBB
Heart Axis is deviated to the right lower quadrant

Which can occur with RBBB

It is most likely SVT with RBBB

Ventricular Tachycardia is less likely

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 214/min.
Brugada Algorithm

Condition 3: Presence of AV Dissociation (Yes)

P waves (arrows) are independent of QRS complexes

It is Ventricular Tachycardia

Wide Complex Tachycardia

QRS Duration 0.18s
Heart Rate 150/min.
Brugada Algorithm

Condition 1: Is the RS Complex in the precordial leads (No)

It is Ventricular Tachycardia

Which is also confirmed by AV Dissociation (arrows)

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers