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In a normal axis, QRS is between -30° and +90°. In contrast to that, left axis deviation (LAD) is defined as QRS axis between −30° and −90°, and right axis deviation is defined as QRS axis greater than +90°, while extreme axis deviation occurs when QRS axis is between -90° and 180°. [3]
If the electrical axis is between -30° and -90° this is considered left axis deviation. If the electrical axis is between +90° and +180° this is considered right axis deviation (RAD). RAD is an ECG finding that arises either as an anatomically normal variant or an indicator of underlying pathology.
LAFB cannot be diagnosed when a prior inferior wall myocardial infarction (IMI) is evident on the ECG. IMI can also cause extreme left-axis deviation, but will manifest with Q-waves in the inferior leads II, III, and aVF. By contrast, QRS complexes in the inferior leads should begin with r-waves in LAFB. [citation needed]
Left axis deviation (QRS of −30° or more) 2 QRS duration ≥0.09 sec 1 Delayed intrinsicoid deflection in V 5 or V 6 (>0.05 sec) 1
Electrocardiography shows right ventricular hypertrophy (RVH), along with right axis deviation. [24] RVH is noted on EKG as tall R-waves in lead V1 and deep S-waves in lead V5–V6. [ 52 ]
The axis may be normal but may be deviated to the left or right. [4] There are also partial blocks of the left bundle branch: "left anterior fascicular block" (LAFB) [5] and a "left posterior fascicular block" (LPFB). [5] This refers to the block after the bifurcation of the left bundle branch.
The hexaxial reference system is a diagram that is used to determine the heart's electrical axis in the frontal plane. The hexaxial reference system, better known as the Cabrera system, is a convention to present the extremity leads of the 12 lead electrocardiogram, [1] that provides an illustrative logical sequence that helps interpretation of the ECG, especially to determine the heart's ...
Electrical alternans is an electrocardiographic phenomenon of alternation of QRS complex amplitude or axis between beats and a possible wandering base-line. It can be seen in cardiac tamponade and severe pericardial effusion and is thought to be related to changes in the ventricular electrical axis due to fluid in the pericardium, as the heart essentially wobbles in the fluid filled ...