Introduction and objectives. It is vital that obstruction of the left main coronary artery (LMCA) is diagnosed early. We investigated the value of ST-segment and QRS-complex vector analysis in identifying LMCA obstruction in acute coronary syndrome.Methods. The study involved 57 consecutive patients with electrocardiographic features suggestive of LMCA obstruction. Both ST-segment and QRS-complex parameter vectors were analyzed.Results. Coronary angiography showed that the obstructed vessel was the LMCA in 20 patients, the left circumflex artery in 19, the right coronary artery in 10, and the left anterior descending artery in three. Five patients had three-vessel disease. An ST vector that was directed between -90 degrees and 180 degrees in the frontal plane was observed in 100% of patients with an LMCA obstruction (P<.001). The specificity of this observation was 78%. An ST vector directed anteriorly or parallel to the horizontal plane was present in 95% of patients (19/20) with an LMCA obstruction (P<.001; specificity 92%). A QRS vector with a left shift >=-30 degrees was observed in 75% (15/20) with LMCA disease (P<.001; specificity 95%). An ST vector directed between -90 degrees and 180 degrees and anteriorly had a sensitivity of 95% and specificity of 100% for LMCA obstruction. An ST vector directed between -90 degrees and 180 degrees combined with a left QRS vector shift >=-30 degrees had a sensitivity of 75% and a specificity of 100% for LMCA obstruction. A simple algorithm combining these observation was able to predict LMCA obstruction in 100% of patients.Conclusions. In acute coronary syndrome, ST-segment and QRS-complex vector analysis can predict the presence of LMCA obstruction.
Electrocardiographic diagnosis of left main coronary artery obstruction using ST-Segment and QRS-complex vector analysis
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