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If lead b is positive, the electrical heart axis can be estimated to lie within the quadrant between axis of lead a and lead b. A simple tool to quickly identify axis deviation (Figure 3) is the popular mnemonic; Reaching for Right Axis Deviation and Leaving for Left Axis Deviation. This refers to the appearance of leads I and II.
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
The heart has several axes, but the most common by far is the axis of the QRS complex (references to "the axis" imply the QRS axis). Each axis can be computationally determined to result in a number representing degrees of deviation from zero, or it can be categorized into a few types.
An important potential finding with echo is McConnell's sign, where only the RV apex wall contracts; [7] it is specific for right heart strain and typically indicates a large PE. [8] On an electrocardiogram (ECG), there are multiple ways RV strain can be demonstrated. A finding of S1Q3T3 [b] is an insensitive [10] sign of right heart strain. [11]
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 ...
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 ...
The American Heart Association has defined a LPFB as: [3] Frontal plane axis between 90° and 180° in adults; rS pattern in leads I and aVL; qR pattern in leads III and aVF; QRS duration less than 120 ms; The broad nature of the posterior bundle as well as its dual blood supply [4] makes isolated LPFB rare. [5]
An R-on-T can initiate torsades. Sometimes, pathologic T-U waves may be seen in the ECG before the initiation of torsades. [19] A "short-coupled variant of torsade de pointes", which presents without long QT syndrome, was also described in 1994 as having the following characteristics: [20] Drastic rotation of the heart's electrical axis