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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 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.
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
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).
Under these criteria, an ECG is positive for an AMI in the presence of LBBB if any of the following criteria are present: ST deviation ≥1 mm (0.1 mV) concordant with QRS polarity in any ECG lead, thus including either: ST depression ≥1 mm (0.1 mV) concordant with QRS polarity, in any ECG lead.
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
First-degree atrioventricular block (AV block) is a disease of the electrical conduction system of the heart in which electrical impulses conduct from the cardiac atria to the ventricles through the atrioventricular node (AV node) more slowly than normal.
Using only conventional ECG criteria to diagnose LVH the diagnostic accuracy was 57%, however the inclusion of the SA significantly improved the diagnostic accuracy to 79%. [ 14 ] The SA is not routinely measured in clinical ECG examination even though the computerized vectorcardiography software is widely available, efficient and is not ...