Electrocardiography vs. vectorcardiography in the diagnosis of left anterior hemiblock associated with inferior wall myocardial infarction: a critical analysis.

The ECG criteria of isolated left anterior hemiblock (LAHB) are well established. However, associated inferior wall myocardial infarction (IMI) can obscure the ECG characteristics of LAHB. In an attempt to evaluate various ECG signs of LAHB in the presence of IMI, three groups of patients were examined. Group I comprised 20 patients with unequivocal vectorcardiographic (VCG) signs of isolated LAHB; Group II included 30 patients with VCG-documented IMI; and the 20 patients in Group III had VCG evidence of IMI with LAHB. Four ECG criteria were evaluated and their average performances in the diagnosis of LAHB were determined. QRS axis above -30 degrees, the presence of terminal S wave in lead II and terminal R wave in lead AVR and delayed intrinsicoid deflection in lead AVL showed average performances of 86.2, 76.7, 68.7 and 60.8% respectively. The ECG criteria in the diagnosis of LAHB are highly sensitive but do not reach the high specificity claimed by other authors.