left axis deviation

It is manifest on the ECG by left axis deviation.

In the setting of right bundle branch block, right or left axis deviation may indicate bifascicular block.

Individuals with a sinus venosus ASD exhibit a left axis deviation of the P wave (not the QRS complex).

Left axis deviation (LAD) is a condition whereby the mean electrical axis of ventricular contraction of the heart lies in a frontal plane direction between -30 and -90 .

The delayed and unopposed activation of the remainder of the left ventricle now results in a shift in the QRS axis leftward and superiorly, causing marked left axis deviation.

In addition to the PR prolongation, individuals with a primum ASD have a left axis deviation of the QRS complex while those with a secundum ASD have a right axis deviation of the QRS complex.

It is important not to call LAFB in the setting of a prior inferior wall myocardial infarction which may also demonstrate left axis deviation due to the initial forces (Q wave in a Qr complex) in leads II, III, and aVF.