Electrocardiographic Terms

Leads.

Leads (recording electrodes) are designated as follows:

Types of Leads	Names
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	−aVR
(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	MCL1

Example: The abnormality appeared in leads V₃ through V₆ [not V₃-V₆ or V_3-6].

Deflections.

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.

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Figure 1. Electrocardiographic deflections (schematic).

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

qR complex

QR-type complex

QRS complex, configuration, axis, duration, etc

qrs complex, etc

QRS-T complex

QS wave, qs wave

QT interval, prolongation, etc (not Q-T)

QTc (corrected QT interval)

R wave, r wave, R′ wave, r′ wave

R-on-T

R-R interval

rS, RS, Rs complex, configuration, etc

R/S (ratio)

rSR′ pattern

S wave, s wave

S′ wave, s′ wave

ST segment, depression, axis, etc (not S-T)

ST-segment abnormality

ST-T segment, elevation, changes, axis, etc (not S-T-T)

T wave, axis, etc

Ta wave (atrial repolarization)

TQ segment

U wave

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).

P-wave duration

Q-wave irregularity

non–Q-wave myocardial infarction

ST-segment depression (not S-T)

The following symbols are used in connection with paced ECGs:

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.

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°.