- Criteria in LBBB
- New LBBB is out!
- A new or presumed new LBBB used to be a STEMI equivalent. In the past few years, increasing literature has suggested that a new LBBB does NOT predict a high likelihood of AMI/acute thrombosis.
- The most recent STEMI Guidelines state that new or presumed new LBBB is no longer an indication for emergent CLA/lytics!Reference:O’Gara PT, Kushner FG, Ascheim DD, et al. 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction. JAC 2013;61(4):e78–e140. PMID: 23256914.
- Left Bundle Branch Block Basics
- LBBB’s cause ST-segment & T wave changes that can make the identification of acute MI difficult
- Patients with LBBB are expected to have ST segment & T wave changes that are discordant to the direction of the QRS complex. This is normal & referred to as the “Rule of Appropriate Discordance”
- ST-segment deviations that are concordant(in same direction) to the QRS complex are abnormal
- Suspected ACS and new or old LBBB with hemodynamic/electrical instability or acute heart failure should go to the cath lab emergentlyReferenceNeeland IJ, Kontos MC, de Lemos JA. Evolving considerations in the management of patients with left bundle branch block and suspected myocardial infarction. J Am Coll Cardiol 2012;60(2):96–105. PMID: 22766335.
- Sgarbossa Criteria
- Sgarbossa criteria can be used to help diagnose AMI in setting of LBBB
- Meeting the criteria in a single lead can be specific for AMI
- The criteria are reviewed below
Concordant STE ≥ 1mm (in any lead) = Most specific for MI
Concordant STD ≥ 1mm in V1, V2, or V3 = Specific for MI
Discordant STE ≥ 5mm = Less specific for MI
- A revised Sgarbossa C rule has been proposed (not yet validated) to increase the diagnostic utility of the rule for STEMI. This revised rule replaces the absolute criterion (discordant STE ≥5 mm) with a proportional criterion (ST-segment to S-wave ratio ≤-0.25). This is consistent with the electrophysiological principle that repolarization voltages should be proportional to depolarization voltages.
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References:
- Smith SW, Dodd KW, Henry TD, et al. Diagnosis of ST-Elevation Myocardial Infarction in the Presence of Left Bundle Branch Block With the ST-Elevation to S-Wave Ratio in a Modified Sgarbossa Rule. Ann Emerg Med. 2012;60(6):766–776. PMID: 22939607.
- Cai Q, Mehta N, Sgarbossa EB, et al. The left bundle-branch block puzzle in the 2013 ST-elevation myocardial infarction guideline: From falsely declaring emergency to denying reperfusion in a high-risk population. Are the Sgarbossa Criteria ready for prime time? American Heart Journal. 2013;166(3):409–413. PMID: 24016487.
- Kontos MC, Aziz HA, Chau VQ, et al. Outcomes in patients with chronicity of left bundle-branch block with possible acute myocardial infarction. American Heart Journal 2011;161(4):698–704. PMID: 21473968.
- Jain S, Ting HT, Bell M, et al. Utility of left bundle branch block as a diagnostic criterion for acute myocardial infarction. Am J Cardiol 2011;107(8):1111–6. PMID: 21296327.
- Chang AM, Shofer FS, Tabas JA, et al. Lack of association between left bundle-branch block and acute myocardial infarction in symptomatic ED patients. Am J Emerg Med 2009;27(8):916–21. PMID: 19857407.
