Sgarbossa’s Criteria for the Diagnosis of MI in LBBB



SGARBOSSA’S CRITERIA FOR DIAGNOSIS OF MYOCARDIAL INFARCTION IN THE PRESENCE OF LBBB

The presence of a complete LBBB makes the diagnosis of myocardial infarction by ECG difficult.

The Decision to Thrombolise

Thrombolysis should be strongly considered in patients without contra-indications to this treatment in the following situations:

1. The development of a new LBBB and clinical features strongly suggestive of myocardial infarction.

2. In all patients with a pre-existing LBBB and a strong clinical picture of myocardial infarction.

Patients with a pre-existing LBBB

Sgarbossa’s Criteria can be used in cases of patients with a pre-existing LBBB to determine the likelihood of myocardial infarction, hence aid in the decision of whether or not to thrombolyse

There are 3 criteria with a points scoring system:

1. ST elevation > 1 mm concordant with the QRS axis (5 points)

2. ST depression > 1 mm in V1 V2 V3 (3 points)

3. ST elevation > 5 mm discordant with the QRS axis (2 points)

The higher the number of total points up to 10, the more likely the diagnosis of myocardial infarction.

For zero points there will still be a 16% chance of myocardial infarction.

For 10 points there will be an almost 100% chance of myocardial infarction.

For practical purposes a score of 3 or more should be treated as myocardial infarction. A score less then this means the diagnosis is much less certain and further evaluation will be necessary

The decision to thrombolyse in this situation is difficult and should be discussed with the ED consultant or the on call cardiologist.

Usually the ECG can be faxed to the cardiologist.

Examples of the Sgarbossa Criteria

References

Sgarbossa EB, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle branch block. N Engl J Med 1996;334

Shlipak MG, et al. Should the electrocardiogram be used to guide therapy for patients with left bundle branch block and suspected myocardial infarction?

JAMA 1999;281: 714-719

Edhouse JA, et al. Suspected myocardial infarction and left bundle branch block: Electrocardiographic indicators of acute ischaemia.

J Accid Emerg Med 1999;16:331-335.

Dr J Hayes

25 February 2002.

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