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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°.
Left ventricular mass can be further estimated based on geometric assumptions of ventricular shape using the measured wall thickness and internal diameter. [7] Average thickness of the left ventricle, with numbers given as 95% prediction interval for the short axis images at the mid-cavity level are: [8] Women: 4 – 8 mm; Men: 5 – 9 mm
Characterizing the size of the left atrium according to its volume is preferred over a single linear dimension since enlargement can be different for different directions. For example, because of the smaller distance in the thoracic cavity between the sternum and spine , compared to the other directions, less room exists for enlargement of the ...
Left anterior fascicular block (LAFB) is an abnormal condition of the left ventricle of the heart, [1] [2] related to, but distinguished from, left bundle branch block (LBBB). It is caused by only the left anterior fascicle – one half of the left bundle branch being defective. It is manifested on the ECG by left axis deviation.
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.
A right bundle branch block typically causes prolongation of the last part of the QRS complex and may shift the heart's electrical axis slightly to the right. The ECG will show a terminal R wave in lead V1 and a slurred S wave in lead I. Left bundle branch block widens the entire QRS, and in most cases shifts the heart's electrical axis to the ...
Ventricular arrhythmias are usually exercise-related, suggesting that they are sensitive to catecholamines. The ventricular beats typically have a right axis deviation. Multiple morphologies of ventricular tachycardia may be present in the same individual, suggesting multiple arrhythmogenic foci or pathways.
Further evidence for the diagnosis can be obtained with an electrocardiogram and a chest radiograph. 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 ...