Left bundle branch block without concordant ST changes is rarely associated with acute coronary occlusion

BackgroundThe Sgarbossa score has been used to identify acute myocardial infarction on ECG in the presence of LBBB but has relied on elevated CK-MB for validation rather than angiographic evidence of vessel occlusion.MethodsWe determined (a) the presence or absence of Sgarbossa criteria with concordant (S-con) or discordant (S-dis) ST changes, (b) the presence of acute coronary occlusion or likely recent occlusion on angiography and (c) the biochemical evidence of myocardial infarction (Troponin T > 0.10 μg/L, Troponin I > 1.0 μg/L) in patients field-triaged with suspected AMI and LBBB.ResultsBetween April 2004 and March 2009, 102 patients had field ECGs transmitted by paramedics for triage - 8 with S-con, 26 with S-dis and 68 with LBBB alone. Acute coronary occlusion was present in 8/8 with S-con but none of the S-dis or LBBB alone patients, and in all 8 S-con patients reperfusion resulted in resolution of S-con changes. Likely culprit lesions with TIMI 3 flow were found in 3 S-dis patients but stenting did not result in resolution of S-dis. LBBB did not resolve in any patient. Troponin was elevated in 26 patients - 11 with occlusion or likely culprit lesions, 15 with non-ischaemic causes.ConclusionsIn the absence of S-con, LBBB is not associated with acute coronary occlusion and should not be used as criteria for reperfusion therapy in myocardial infarction.