MicroEKG Manual

Chamber Enlargement


MicroEKG Details

Right atrial enlargement:

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.

The increased voltage is best seen in the “inferior” leads — those that see electrical activity moving from the top to bottom — II, III, and F. The lead most likely to show the right atrial enlargement is lead II.

e_hi_p.gif (3708 bytes)

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]

Left atrial enlargement:

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).
The long or abnormally shaped P wave occurs because of delay in electrical activation of the enlarged left atrium, as electricity moves leftward from the SA node. A P wave longer than 0.11 milliseconds is diagnostic of left atrial enlargement (LAE).

e_bi_p.gif (3640 bytes) Two other abnormalities indicate LAE. A “double hump” or notched P wave is diagnostic of LAE if the peaks are one small box or more apart. A biphasic P wave indicates left atrial enlargement if the downward portion of the P wave is one box or larger in both depth and length.

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]

Atrial Enlargement Criteria
P > 2.5 height                                =      RAE
P > 0.11 sec
     or P notch > 1 box width
     or P biphasic > 1 box square    =      LAE

Right ventricular hypertrophy:

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.

Other findings in RVH include right axis deviation, taller R waves in the right precordial leads (V1-V3), and deeper S waves in the left precordials (V4-V6). The T wave is inverted in V1 (and often in V2). RVH Criteria
R in V1 > 7 mm or > S wave
T in V1 inverted
Right axis deviation
S waves in V5-V6

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.

mi_rvh.gif (5509 bytes)

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:

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.

Summary of LVH Criteria
1) R-I + S-III >25 mm
2) S-V1 + R-V5 >35 mm
3) ST-Ts in left leads
4) R-L >11 mm
5) LAE + other criteria

Positive Criteria: 1=possible 2=probable 3=definite

LVH Criteria #1:
Increased limb lead QRS voltage: R in lead I plus S in lead III greater than 25 mm.

LVH Criteria #2:
Increased precordial QRS voltage: S in lead V1 plus R in either V5 or V6 greater than 35 mm.

LVH Criteria #3:
Typical ST and T abnormalities: ST depression or T wave inversion (or both) in the “lateral” leads (I, L, V4-V6)

LVH Criteria #4:
Large leftward voltage: R wave in lead L greater than 11 mm.

LVH Criteria #5:
Left atrial enlargement: Wide (greater than 0.11 msec) P wave. This criterion is used IN SUPPORT of the diagnosis, not alone.

mi_lvh.gif (6139 bytes)
Example of LVH  [Chapter Menu]

Go to Chapter 6, Diagnosis of Q Waves

All material referenced through this menu is excerpted from copyrighted works by Bruce Argyle, MD. You are welcome to use selected portions, as long as appropriate credit is given. The credit for the text referenced through this menu is:

Argyle, B., MicroEKG Computer Program Manual.
Mad Scientist Software, Alpine, Utah

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