Why We Use the Sgarbossa Rule in LBBB

On the Shoulders of Giants

Reading STEMI in LBBB
Reading acute MI in the setting of the marked repolarization abnormalities of left bundle branch block (LBBB) is challenging.  This study provided a systematic way to read acute MI despite LBBB and found three criteria were useful in making the diagnosis.  These criteria were 96% specific but only 36% sensitive in the small validation cohort.  The three are quoted here.

  1. ST-segment elevation of 1 mm or more that was concordant with (in the same direction as) the QRS complex; [5 points]

  2. ST-segment depression of 1 mm or more in lead V1, V2, or V3; [3 points]

  3. and ST-segment elevation of 5 mm or more that was disconcordant with (in the opposite direction from) the QRS complex. [2 points]  

Subsequent research by Smith et al. in 2012 showed that modification of the Sgarbossa criteria markedly improved diagnostic accuracy for an actual occluded artery at arteriogram.  The modified criteria were unweighted (any positive criterion was considered a STEMI), with the first two ECG findings the same as the original Sgarbossa rule.  The third aspect of the rule was altered so that instead of an absolute height of ST elevation of 5mm or more, the ratio of ST deviation (up or down) to the S wave of -0.25 or more was considered positive.  See the figure.  Sensitivity jumped from 36% for weighted Sgarbossa to 91% with the Smith's modified version, and specificity went down from 96% to 90% respectively.

From https://www.ncbi.nlm.nih.gov/pubmed/22939607

From https://www.ncbi.nlm.nih.gov/pubmed/22939607

Spoon Feed
Sgarbossa criteria can help interpret the ECG for STEMI in the setting of LBBB.  Subsequent modifications make it even more accurate.

Life in the Fast Lane has an outstanding review of Sgarbossa as does emDocs.  Dr. Smith himself also wrote of a nice case for EP Monthly about his modified criteria.


Abstract

N Engl J Med. 1996 Feb 22;334(8):481-7.

Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators.

Sgarbossa EB1, Pinski SL, Barbagelata A, Underwood DA, Gates KB, Topol EJ, Califf RM, Wagner GS.

Author information:

1Cleveland Clinic Foundation, Department of Cardiology, OH 44195, USA.

Erratum in

  • N Engl J Med 1996 Apr 4;334(14):931.

Comment in

Abstract

BACKGROUND:

The presence of left bundle-branch block on the electrocardiogram may conceal the changes of acute myocardial infarction, which can delay both its recognition and treatment. We tested electrocardiographic criteria for the diagnosis of acute infarction in the presence of left bundle-branch block.

METHODS:

The base-line electrocardiograms of patients enrolled in the GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) trial who had left bundle-branch block and acute myocardial infarction confirmed by enzyme studies were blindly compared with the electrocardiograms of control patients who had chronic coronary artery disease and left bundle-branch block. The electrocardiographic criteria for the diagnosis of infarction were then tested in an independent sample of patients presenting with acute chest pain and left bundle-branch block.

RESULTS:

Of 26,003 North American patients, 131 (0.5 percent) with acute myocardial infarction had left bundle-branch block. The three electrocardiographic criteria with independent value in the diagnosis of acute infarction in these patients were an ST-segment elevation of 1 mm or more that was concordant with (in the same direction as) the QRS complex; ST-segment depression of 1 mm or more in lead V1, V2, or V3; and ST-segment elevation of 5 mm or more that was disconcordant with (in the opposite direction from) the QRS complex. We used these three criteria in a multivariate model to develop a scoring system (0 to 10), which allowed a highly specific diagnosis of acute myocardial infarction to be made.

CONCLUSIONS:

We developed and validated a clinical prediction rule based on a set of electrocardiographic criteria for the diagnosis of acute myocardial infarction in patients with chest pain and left bundle-branch block. The use of these criteria, which are based on simple ST-segment changes, may help identify patients with acute myocardial infarction, who can then receive appropriate treatment.

PMID: 8559200 [PubMed - indexed for MEDLINE]