Left anterior hemiblock (LAHB)
(Click on the image for an enlarged view)
Left anterior hemiblock (LAHB) is manifest as rS complexes in inferior leads (II, III and aVF) causing left axis deviation in the absence of other causes of left axis deviation like an inferior wall infarction. Some authors suggest that if there are QS complexes in inferior leads, it suggests LAHB along with inferior wall myocardial infarction. qR complexes are seen in leads I and aVL in LAHB. Isolated LAHB may not have much prognostic significance. It is commonly associated with anterior wall myocardial infarction. LAHB can also be seen in a variety of congenital heart diseases. Many a time no associated condition can be detected along with LAHB. This ECG also shows clockwise rotation with rS complexes in V1 to V6.
QRS axis in LAHB – computer generated
This image shows the computer generated QRS axis near -90 degrees (left upper quadrant). P wave and T wave axes are seen in the left lower quadrant.