Right atrial enlargement (RAE) is diagnosed by the presence of a P wave 2.5 millimeters or greater in height. The P wave often has a sharp, peaked appearance. This increased voltage is caused by hypertrophy or acute strain of right atrial tissue.
Causes of right atrial enlargement include COPD, mitral stenosis, mitral regurgitation, or pulmonary emboli. Because RAE is so frequently seen in chronic pulmonary disease, the peaked P wave is often called P pulmonale. [Chapter Menu]
Dilation or hypertrophy of the left atrium may increase the DURATION of the P wave. (Recall that right atrial enlargement causes an increase in the HEIGHT or amplitude of the P wave.) The P wave is normally less than 0.11 msec (just under three small boxes).
Left atrial enlargement often occurs in mitral valve disease (either stenosis or insufficiency). Because of this association, a broad notched P wave is often called P mitrale. In addition LAE often occurs with any cause of left ventricular hypertrophy. [Chapter Menu]
Right ventricular hypertrophy (RVH) increases the height of the R wave in V1. An R wave in V1 that is greater than 7 boxes in height, or larger than the S wave, is suspicious for RVH. Other findings are necessary to confirm the ECG diagnosis.
True posterior infarction may also cause a tall R wave in V1, but the T wave is usually upright, and there is usually some evidence of inferior infarction (ST-T changes or Qs in II, III, and F).
A large R wave in V1, when not accompanied by evidence of infarction, nor by evidence of RVH (right axis, inverted T wave in V1), may be benign counter-clockwise rotation of the heart. This can be seen with abnormal chest shape.
RVH may occur with any process that raises the ejection work in the right ventricle. This may be volume overload such as atrial septal defect or tricuspid regurgitation, or may be pressure overload such as pulmonary stenosis. Examples of pressure-load causes of RVH include pulmonary stenosis or primary pulmonary hypertension, pulmonary disease (COPD or pulmonary emboli), large ventricular septal defect, or pulmonary hypertension due to mitral valve disease. [Chapter Menu]
Left ventricular hypertrophy is caused by increased loads on the left ventricle. Examples are hypertension, aortic stenosis or regurgitation, mitral regurgitation, or subaortic stenosis.
Left ventricular hypertrophy (LVH) may be difficult to diagnose with certainty from the ECG. Different scoring criteria have been recommended. One of the simplest uses five criteria, with the certainty of diagnosis based on the number of criteria present. If one is present, diagnose possible LVH; if two, probable LVH; if three are found, definite LVH. The scoring criteria are discussed in detail on the next page. Please refer to the sample ECG.
LVH Criteria #1:
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