MI Diagnosis in LBBB or paced rhythm: Difference between revisions

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Image:E000003.jpg|Case 3: Acute MI in a patient with LBBB
Image:E000003.jpg|Case 3: Acute MI in a patient with LBBB
Image:E000002.jpg|Case 3: Non-ischemic ECG in this patient
Image:E000002.jpg|Case 3: Non-ischemic ECG in this patient
Image:E000406.jpg|thumb|right|Myocardial infarction in a pacemaker patient. The ECG shows LBBB as expected during pacing, however overt repolarization abnormalities are present.
Image:E000406.jpg|Myocardial infarction in a pacemaker patient. The ECG shows LBBB as expected during pacing, however overt repolarization abnormalities are present.
Image:E000405.jpg|thumb|right|Myocardial infarction post primary PCI in a pacemaker patient
Image:E000405.jpg|Myocardial infarction post primary PCI in a pacemaker patient


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Revision as of 14:15, 28 February 2011

Changes in LBBB during ischemia

In case of a left bundle branch block (LBBB), infarct diagnosis based on the ECG is difficult. The baseline ST segments and T waves tend to be shifted in a discordant direction with LBBB, which can mask or mimic acute myocardial infarction. However, serial ECGs may show a moving ST segment during ischemia secondary to dynamic supply versus demand characteristics. A new LBBB is always pathological and can be a sign of myocardial infarction. The criteria (Sgarbossa [1]) that can be used in case of a LBBB and suspicion of infarction are:

  • ST elevation > 1mm in leads with a positive QRS complex (concordance in ST deviation) (score 5)
  • ST depression > 1 mm in V1-V3 (concordance in ST deviation) (score 3)
  • ST elevation > 5 mm in leads with a negative QRS complex (inappropriate discordance in ST deviation) (score 2). This criterium is sensitive, but not specific for ischemia in LBBB. It is however associated with a worse prognosis, when present in LBBB during ischemia.[2]

At a score-sum of 3, these criteria have a specificity of 90% for detecting a myocardial infarction.

Examples

References

  1. Sgarbossa EB, Pinski SL, Barbagelata A, Underwood DA, Gates KB, Topol EJ, Califf RM, and Wagner GS. 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. N Engl J Med. 1996 Feb 22;334(8):481-7. DOI:10.1056/NEJM199602223340801 | PubMed ID:8559200 | HubMed [LBTB]
  2. Wong CK, French JK, Aylward PE, Stewart RA, Gao W, Armstrong PW, Van De Werf FJ, Simes RJ, Raffel OC, Granger CB, Califf RM, White HD, and HERO-2 Trial Investigators. Patients with prolonged ischemic chest pain and presumed-new left bundle branch block have heterogeneous outcomes depending on the presence of ST-segment changes. J Am Coll Cardiol. 2005 Jul 5;46(1):29-38. DOI:10.1016/j.jacc.2005.02.084 | PubMed ID:15992631 | HubMed [Wong]

All Medline abstracts: PubMed | HubMed