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The hexaxial reference system is a diagram that is used to determine the heart's electrical axis in the frontal plane.. In electrocardiography, left axis deviation (LAD) is a condition wherein the mean electrical axis of ventricular contraction of the heart lies in a frontal plane direction between −30° and −90°.
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.
Beyond +105° is right axis deviation and beyond −30° is left axis deviation (the third quadrant of −90° to −180° is very rare and is an indeterminate axis). A shortcut for determining if the QRS axis is normal is if the QRS complex is mostly positive in lead I and lead II (or lead I and aVF if +90° is the upper limit of normal).
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]
On ECG a left axis deviation is generally found in ostium primum ASD, but an RSR pattern (M pattern) in V1 is characteristic. Fixed splitting of the second heart sound (S2) occurs because of equal filling of the left and right atria during all phases of the respiratory cycle. [citation needed] ECG of a patient with Ostium primum ASD
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 ...
Nonetheless, the ECG is used to assist with the diagnosis of RVH. A post mortem study on 51 adult male patients concluded that anatomical RVH may be diagnosed using one or more of the following ECG criteria: [8] Right axis deviation of more than (or equal to) 110° (see hexaxial reference figure) R-wave dominant over S-wave in V1 or V2
ECG will typically show a left axis deviation, while the chest X-ray may show pulmonary oligaemia or hyperaemia. The definitive investigation is, as in all congenital heart diseases, an echocardiogram, although the aforementioned tests along with clinical features might be sufficient for most cases.