15.3.1 Electrocardiographic Terms
International standardization of electrocardiographic nomenclature dates back to the mid-20th century.1-4
The preferred abbreviation for electrocardiogram and electrocardiographic in JAMA and the Archives Journals is ECG, not EKG. In the following examples of ECG terms note the use of capitals, lowercase letters, subscripts, and hyphens.
Leads (recording electrodes) are designated as follows:
Types of Leads
Standard (bipolar) leads
I, II, III
Augmented limb leads/unipolar extremity leads
(a, augmented; V, voltage; R, right arm; L, left arm; F, foot)
aVR, aVL, aVF
Inverted aVR lead
(Unipolar) precordia (chest) leads
V1, V2, V3, V4, V5, V6, V7, V8, V9
Right precordial leads
V1R, V2R, V3R, V4R, V5R, V6R
Modified chest lead using V1
Example: The abnormality appeared in leads V3 through V6 [not V3-V6 or V3-6].
The main deflections of the ECG (see Figure 1) are named in alphabetical sequence (P, Q, R, S, T, U), a usage that dates back to the inventor, Willem Einthoven.2 Other deflections use initial letters of the entity being described.
As a guide, hyphens usually do not link deflection terms in the same PQRSTU complex (eg, QT) but do link deflections in different waves (eg, R-R), with the exception of ST-T. The following are examples of terms descriptive of deflections and patterns in ECG tracings:
delta wave (preferred over Δ wave)
F wave (atrial flutter wave)
f wave (atrial fibrillation wave)
J point, J junction (junction of QRS complex and ST segment; do not confuse with the J curve in hypertension)
J-ST axis, vector
P wave, axis, etc
PR interval, segment, etc (not P-R)
Q wave, q wave
QRS complex, configuration, axis, duration, etc
qrs complex, etc
QS wave, qs wave
QT interval, prolongation, etc (not Q-T)
QTc (corrected QT interval)
R wave, r wave, R′ wave, r′ wave
rS, RS, Rs complex, configuration, etc
S wave, s wave
ST segment, depression, axis, etc (not S-T)
ST-T segment, elevation, changes, axis, etc (not S-T-T)
T wave, axis, etc
Ta wave (atrial repolarization)
When terms such as the foregoing are used as modifiers, use a hyphen before the modifying noun (see also 8.3, Punctuation, Hyphens and Dashes).
non–Q-wave myocardial infarction
ST-segment depression (not S-T)
The following symbols are used in connection with paced ECGs:
interval from atrial stimulus to succeeding ventricular stimulus
interval from atrial stimulus to conducted spontaneous ventricular depolarization
interval from spontaneous atrial depolarization to succeeding “atrial-synchronous” ventricular stimulus
Capital letters are used to describe generic ECG deflections.
Improper paper speed will spuriously alter the QRS configuration. [not qrs configuration]
In reference to an individual ECG tracing, or in descriptions of some specific ECG patterns, capitals may indicate larger waves and lowercase letters smaller waves; in practice, this most often applies to the Q, R, and S waves.
Pathologic Q waves occur in myocardial infarction.
The q wave in aVF and the Rr′ pattern in lead V3 in this patient’s ECG were considered normal findings.
An rSR′ complex in the anterior chest leads and qRs in the left chest leads may indicate right bundle-branch block.
Lead and tracing terms may be combined to describe pattern and location together.
R wave in lead I
R wave in aVL
S wave in lead III
R wave in V3
Prominence of S wave in lead I, Q wave in lead III, and T-wave inversion in lead III
SV1 + RV5
Sum of voltages of S wave in V1 and R wave in V5
The P axis, QRS axis, ST axis, and T axis are specified with a plus or minus sign followed by the number of degrees in arabic numerals, eg, +60°, −30°.