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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°.
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 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
Aneurysmal dilatation is seen in 50% of cases at autopsy. It usually occurs in the diaphragmatic, apical, and infundibular regions (known as the triangle of dysplasia). The left ventricle is involved in 50–67% of individuals. If the left ventricle is involved, it is usually late in the course of disease, and confers a poor prognosis.
The most common causes of cardiomegaly are congenital (patients are born with the condition based on a genetic inheritance), high blood pressure (which can enlarge the left ventricle causing the heart muscle to weaken over time), and coronary artery disease. In the latter case, the disease creates blockages in the heart's blood supply, leading ...
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.
When left bundle-branch block (LBBB) is accompanied by right axis deviation (RAD), the rare combination is considered to be highly suggestive of dilated or congestive cardiomyopathy. [29] [30] Echocardiogram shows left ventricular dilatation with normal or thinned walls and reduced ejection fraction.
An ECG may show left ventricular hypertrophy and signs of left heart strain. [31] Left axis deviation can be a sign of advanced disease. [ 31 ] An echocardiogram can be helpful in determining the root cause of the disease, as it will clearly show aortic root dilation or dissection if it exists. [ 31 ]