So it’s a trifascicular block ?

Well yes and no.

Many people refer to the combination of bifascicular block with a 1st or 2nd degree AV block as a ‘trifascicular block’, this term is obviously incorrect as a block of all three fascicles should result in complete heart block.

Further to the inaccurate nature of the term the AHA 2009 Recommendations for the Standardization and Interpretation of the Electrocardiogram specifically recommended the term ‘trifascicular block’ not be used due to the variation in anatomy and pathology producing the pattern.

On this surface ECG it isn’t possible to tell whether all three fascicles are affected as the pr prolongation may be due to disease at the AV node, the left posterior fascicle, or the His bundle.
In this case the concern is whether the patient has had transient complete heart block causing syncope, a situation associated with an increased risk of sudden death and high mortality rate.
These patients with bifascicular block, pr prolongation and a history of syncope or likely arrhythmia, should be referred to cardiology team for telemetry, review of current medications, and consideration for PPM insertion.

The AHA 2008 guidelines for PPM insertion are clear that an incidental bifascicular block with pr prolongation in the asymptomatic patient does not warrant PPM insertion (LoE: B, Class III recommendation).

Syncope Rules

San Francisco Syncope Rule

Risk factors, any one or more places patient in ‘high risk’ group. CHESS mnemonic.

  • C= History cardiac failure
  • H =Haematocrit <30%
  • E = Abnormal ECG
  • S = Shortness of breath
  • S = Triage Systolic BP <90 mmHg

Study outcome measure was serious outcome within 30 days, predefined as death, MI, stroke, SAH, arrhythmia, haemorrhage, or any condition causing re attendance and admission.
The initial validation study quotes sensitivity of 98% and specificity of 56% for predicting high risk group / adverse outcome, although other studies of the SFSR have shown a lower sensitivity and specificity.

OESIL Rule

Score total (1 point each for)

  • Age >65yr
  • History cardiovascular disease
  • Syncope without prodrome
  • Abnormal ECG 
    • (LAD, hypertrophy, ischaemia, conduction disturbance / blocks)

All cause 12 month mortality by score

  • 0 point = 0 %
  • 1 point = 0.8%
  • 2 points = 19.6%
  • 3 points = 34.7%
  • 4 points = 57.1%

As you can see a score of 2 or more is considered high risk.

The criticism of these rules is based on their limited sensitivity and lack of specificity