T-wave changes secondary to left anterior hemiblock as shown by study of intermittent and alternating patterns.

T-wave changes in spontaneous intermittent and alternating LAH have been described. Attention has been called to the fact that, with the onset of LAH conduction, the T-wave axis shifts oppositely to that of the QRS, thus widening the QRS-T angle in the frontal plane by about 95 degrees. This has the effect of causing T-waves to become upright in leads II, III and AVF, even in those in whom T-waves were previously inverted. This described dicordance of QRS and T-wave axes is considered as evidence that LAH conduction is in fact a true conduction abnormality. As a corollary, an inverted T-wave in leads II, III or AVF in the presence of LAH is a primary abnormality and may be an indication of inferior wall myocardial ischemia or infarction. T-waves are lowered but not inverted in lead I as a result of LAH conduction and precordial leads are variably but not significantly altered.