ECG Diagnosis of Brugada Syndrome

 

Brugada Syndrome: ECG Diagnosis Made Simple

Brugada syndrome is an inherited primary electrical heart disease characterized by an increased risk of sudden cardiac death due to ventricular arrhythmias. Because patients often have a structurally normal heart, the electrocardiogram (ECG) plays a central role in its diagnosis.

Among the ECG-based tools, two measurements have gained particular importance:

✔️ The β-angle

✔️ The “Base of the Triangle” in the r′ wave

Both help differentiate true Brugada patterns from benign right bundle branch block (RBBB)-like variants.

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1. Recognizing the Brugada ECG Pattern

The 3 Classical ECG Patterns

Brugada patterns are identified in the right precordial leads (V1–V3), ideally placed higher (V1–V2 in 2nd intercostal space) to increase diagnostic sensitivity.

🔸 Type 1 Brugada Pattern (Diagnostic)

Coved ST-segment elevation ≥ 2 mm

Followed by a negative T-wave

Characteristic “shark fin” or “coved” appearance

🔸 Type 2 & 3 Patterns (Suggestive but Not Diagnostic)

These show a saddleback appearance and may need drug challenge (ajmaline, flecainide) to unmask a diagnostic type 1 pattern.

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2. Why the β-Angle and Triangle Base Matter

Not all r′ patterns in V1–V2 are Brugada. Some are benign, especially in athletes or due to normal variants.

The β-angle and triangle base improve diagnostic accuracy by assessing the shape of the r′ wave seen in Brugada syndrome.

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3. How to Measure the β-Angle

The β-angle is the angle between:

1. The descending limb of the r′ wave

2. A horizontal line drawn at 5 mm below the r′ peak

🔧 Step-by-Step Measurement

1. Identify the r′ peak in lead V1 or V2.

2. From the r′ peak, measure 5 mm downward (vertically).

3. Draw a horizontal line at that level.

4. Draw a line along the descending arm of the r′.

5. The angle where they meet is the β-angle.

📌 Diagnostic Cutoff

β-angle ≥ 58° → Suggestive of Brugada syndrome

Smaller angles usually suggest benign r′ variants or incomplete RBBB.

Why it's useful

Brugada r′ waves tend to have a wide, slow descending slope, producing a large β-angle.

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4. How to Measure the “Base of the Triangle”

Another method looks at the base width of the r′ wave when drawn as a triangle.

🔧 Step-by-Step Measurement

1. Identify the r′ peak.

2. Draw vertical lines down from both the ascending and descending limbs of the r′ to the isoelectric line.

3. The distance between these two points is the base of the triangle.

📌 Diagnostic Cutoff

Base ≥ 3.5 mm → Suggestive of Brugada

Narrow base → More likely a benign r′ variant

Physiological Meaning

A wide base indicates slower conduction in the right ventricular outflow tract — characteristic in Brugada syndrome.

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5. Practical Pearls

Always record high intercostal V1–V2 to increase sensitivity.

Measure both the β-angle and triangle base if unsure.

Use multiple beats to avoid misinterpreting artifact.

Remember: only Type 1 pattern is diagnostic.

Consider sodium-channel blocker testing if suspicion remains high.

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6. Summary Table

Feature Brugada r′ Benign r′ Variant

β-angle ≥58° <58°

Triangle base ≥3.5 mm <3.5 mm

ST segment Elevated (coved) Normal

T-wave Negative Usually upright

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Conclusion

Brugada syndrome remains a challenging diagnosis, but using structured ECG criteria helps identify high-risk patients early. The β-angle and triangle base measurements add valuable precision, helping distinguish true Brugada patterns from benign variants.