ECG criteria
- ECG criterion (primary): spontaneous type 1 pattern (J-point elevation ≥2 mm followed by a descending coved ST segment and a negative T wave, with no isoelectric interval) in the right precordial leads V1–V2 in standard or high position — 3.5 points
- ECG criterion: fever-induced type 1 pattern — 3 points
- ECG criterion: type 1 pattern induced by a sodium channel blocker provocative test (without a baseline spontaneous type 2/3 pattern) — 2 points; if the test converts a baseline type 2 or 3 pattern to type 1 — 1 point
- Clinical manifestations: resuscitated cardiac arrest or documented spontaneous VT/VF — 3 points; nocturnal agonal respiration — 2 points; syncope likely to be arrhythmogenic — 2 points; syncope of unknown origin — 1 point
- Family history: definitive Brugada syndrome in a first- or second-degree relative — 2 points; type 1 ECG pattern in a relative — 1 point; unexplained sudden cardiac death in a relative under 45 years of age — 0.5 points
- Genetic result: pathogenic or likely pathogenic SCN5A variant — 0.5 points; variants in other genes putatively associated with Brugada syndrome require expert interpretation and do not constitute a standard genetic criterion of the scale on their own
- Final interpretation: score ≥3.5 points — probable/definite diagnosis with a confirmed valid type 1 pattern and excluded phenocopies; 2–3 points — possible; <2 points — diagnosis unlikely
What it looks like on ECG
The key finding around which the scale is built is the Brugada type 1 pattern in leads V1–V2 (standard 4th intercostal space position or high 2nd–3rd intercostal space position). This is a J-point elevation ≥2 mm with a coved ST segment smoothly transitioning into a negative T wave, with no isoelectric baseline between ST and T.
The type 2 pattern is described separately and follows a different clinical scoring logic: a saddleback ST morphology, J-point elevation ≥2 mm, residual ST elevation in the saddle ≥1 mm, and the terminal part of the T wave being positive or biphasic. Type 2 on its own does not award ECG points — its conversion to type 1 during a sodium channel blocker provocative test is what matters (1 point); if the test induces type 1 without a baseline type 2/3 pattern, 2 points are awarded.
| Pattern | ST shape | Scale score |
|---|---|---|
| Type 1 spontaneous | coved, J ≥2 mm | 3,5 |
| Type 1 associated with fever | coved | 3 |
| Type 1 induced by provocative test (without baseline type 2/3) | coved | 2 |
| Type 2/3 converting to type 1 on provocative test | saddleback → coved | 1 |
The diagnostic pattern is identified in the right precordial leads; changes in other leads are not mandatory but may occur (e.g., early repolarization signs in inferior or lateral leads) and should be evaluated in the clinical context. The overall QRS morphology should also be checked and structural right ventricular pathology ruled out.
Mechanism
The underlying mechanism of the syndrome is cardiomyocyte sodium (less commonly calcium and potassium) channel dysfunction, most frequently due to a mutation in the SCN5A gene encoding the alpha subunit of the Nav1.5 sodium channel. No single mechanism has been established, and several models are under discussion. The repolarization model hypothesizes a reduction of inward sodium current in epicardial cells of the right ventricular outflow tract (RVOT), creating a transmural action potential gradient between the epicardium and endocardium, which forms the J-point and ST-segment elevation in the right precordial leads; this gradient is viewed as the substrate for phase 2 reentry—one of the triggering mechanisms for polymorphic VT and VF. The depolarization model explains the same ECG changes by local conduction slowing and a structural arrhythmogenic substrate in the RVOT. The scale does not describe the mechanism itself, but rather systematizes the probability that the clinician is dealing with this specific channelopathy syndrome rather than a phenocopy.
Causes
- Hereditary Brugada syndrome (mutations in SCN5A and other sodium/calcium channel genes)
- Fever is a frequent trigger for the manifestation of the type 1 pattern
- Brugada phenocopies: electrolyte disturbances (hyperkalemia), sodium channel blocker toxicity (tricyclic antidepressants, cocaine, certain antiarrhythmics), mechanical compression, or ischemia of the right ventricular outflow tract
- Structural diseases of the right ventricle (arrhythmogenic cardiomyopathy) — must be excluded before making a diagnosis
Differential diagnosis
- Incomplete right bundle branch block — differs in morphology: RBBB has a true S wave in lateral leads and a typical rSR' without coved ST
- Early repolarization syndrome — ST elevation is more diffuse, without the characteristic coved shape and without a subsequent negative T wave specifically in V1–V2
- Brugada phenocopy in the setting of hyperkalemia or sodium channel blocker toxicity — the pattern usually resolves after electrolyte correction or drug discontinuation, but this is not an absolute criterion: fever, drugs, and electrolyte imbalances can also unmask a latent hereditary syndrome, so differentiation requires clinical assessment, exclusion of structural and toxic causes, and interpretation in context rather than relying solely on ECG dynamics
- Misplaced V1–V2 electrodes (incorrect placement above the 4th intercostal space) can mimic the pattern — verified by repeat recording in the standard position
Clinical significance and management
The Shanghai score helps structure the diagnostic process when an ECG finding (especially type 2 or induced type 1) does not provide a definitive diagnosis on its own. With a spontaneous type 1, the diagnosis can be made based on the ECG alone, but the score still takes clinical presentation into account for risk stratification.
During interpretation, the physician must: document the exact localization and morphology of the pattern, repeat the ECG in high V1–V2 leads if suspected, take a detailed history regarding syncope, nocturnal symptoms, and sudden death in relatives, refer for genetic testing and, if necessary, for a sodium channel blocker provocative test under controlled monitoring conditions.
All patients with suspected Brugada syndrome should be referred to a cardiac electrophysiologist. The total score alone does not determine the indications for implantable cardioverter-defibrillator (ICD) implantation. For secondary prevention, an ICD is indicated after a survived cardiac arrest due to VF or polymorphic VT, as well as for documented spontaneous sustained VT, especially with hemodynamic instability. For primary prevention, decisions are made based on the clinical profile: a spontaneous type 1 pattern combined with probable arrhythmogenic syncope provides the basis for considering or recommending an ICD in accordance with current guidelines; the Shanghai score value itself is not an indication. Asymptomatic patients do not routinely receive ICD implants.
Common interpretation errors
- Awarding maximum points for a type 2 pattern without specifying that it converts to type 1 during a provocative test
- Ignoring high V1–V2 leads — the pattern may only be visible there
- Diagnosing Brugada syndrome based on ECG alone without excluding phenocopies (fever, electrolytes, medications)
- Confusing the Brugada pattern (ECG finding) with Brugada syndrome (diagnosis including clinical features) when tallying points
- Automatic referral for ICD implantation based on the total score without evaluating the clinical context and prevention type
1. How many points does a spontaneous Brugada type 1 pattern on a standard ECG yield on the Shanghai score?
Spontaneous type 1 in V1–V2 is the main ECG criterion of the score and awards the maximum 3.5 points.
2. At what total score on the Shanghai scale is the diagnosis of Brugada syndrome considered probable?
A threshold of ≥3.5 points is accepted as indicative of a probable or definite diagnosis of Brugada syndrome when phenocopies are excluded.
3. How many points are awarded if a type 2 pattern converts to type 1 during a sodium channel blocker provocative test?
Conversion of a baseline type 2 or 3 pattern to type 1 during the test is awarded 1 point; 2 points are given only for an induced type 1 pattern without a baseline type 2/3 pattern.
Frequently asked questions
What is the Shanghai Brugada Score System?
This is a scoring system that aggregates ECG findings, clinical symptoms, family history, and genetic results to assess the probability of Brugada syndrome. The higher the total score, the more confident the diagnosis can be established.
How many points are needed to diagnose Brugada syndrome?
A score of 3.5 points or higher makes the diagnosis probable or definite when a valid type 1 pattern is confirmed and phenocopies are excluded. A score of 2–3 points is considered possible and requires further evaluation; less than 2 points makes the diagnosis unlikely.
Can the diagnosis be made based on ECG alone without the scoring system?
Yes, a spontaneous type 1 pattern in V1–V2 alone yields 3.5 points, which is sufficient for the diagnosis even without clinical symptoms, but it is important to exclude phenocopies before making a final conclusion.
How does a type 2 pattern differ from a type 1 pattern in terms of scoring?
A type 2 pattern alone does not award ECG points. If a provocative test with a sodium channel blocker converts a baseline type 2 or 3 pattern to type 1, 1 point is awarded; if the test induces a type 1 pattern without a baseline type 2/3 pattern, 2 points are awarded.
Does a high score on the scale mean an implantable cardioverter-defibrillator is needed?
No. A high score on the scale indicates a probable diagnosis, but indications for an ICD are determined separately: for secondary prevention, by a history of cardiac arrest due to VF/polymorphic VT or documented sustained VT, and for primary prevention, by a combination of clinical risk factors, including a spontaneous type 1 pattern and probable arrhythmic syncope.
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Related terms
More in the section "Criteria, Formulas, Algorithms"
Sources
- Surawicz B., Knilans T. Chou's Electrocardiography in Clinical Practice
- AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the ECG, 2009
- Orlov V.N. Guide to Electrocardiography
Educational material for medical students and physicians. Does not replace clinical guidelines and physical examination; the ECG must always be interpreted in conjunction with the clinical picture.