Ecg Waves on ECG Library – LITFL Basics

Osborn Wave (J Wave)

Mon, 21 Jul 2025 00:00:00 +0000

Osborn Wave (J Wave) Overview

The Osborn wave (J wave) is a positive deflection seen at the J point in precordial and true limb leads. It is most commonly associated with hypothermia. These changes will appear as a reciprocal, negative deflection in aVR and V1.

The J point in the ECG is the point where the QRS complex joins the ST segment. It represents the approximate end of depolarization and the beginning of repolarization as determined by the surface ECG. There is an overlap of around 10ms.

Q Wave

Tue, 08 Oct 2024 00:00:00 +0000

The Q Wave

A Q wave is any negative deflection that precedes an R wave

The Q wave represents the normal left-to-right depolarisation of the interventricular septum
Small ‘septal’ Q waves are typically seen in the left-sided leads (I, aVL, V5 and V6)

Q waves in context

Q waves in different leads

Small Q waves are normal in most leads
Deeper Q waves (>2 mm) may be seen in leads III and aVR as a normal variant
Under normal circumstances, Q waves are not seen in the right-sided leads (V1-3)

Pathological Q Waves

Q waves are considered pathological if:

T wave

Tue, 08 Oct 2024 00:00:00 +0000

T wave Overview

The T wave is the positive deflection after each QRS complex. It represents ventricular repolarisation.

Normal T wave characteristics

Upright in all leads except aVR and V1
Amplitude < 5mm in limb leads, < 10mm in precordial leads (10mm males, 8mm females)
Duration relates to QT interval

T wave abnormalities

Peaked T waves
Hyperacute T waves
Inverted T waves
Biphasic T waves
‘Camel Hump’ T waves
Flattened T waves

Peaked T waves

U Wave

Tue, 08 Oct 2024 00:00:00 +0000

U wave Overview

The U wave is a small (0.5 mm) deflection immediately following the T wave

U wave is usually in the same direction as the T wave.
U wave is best seen in leads V2 and V3.

Source of the U wave

The source of the U wave is unknown. Three common theories regarding its origin are:

Delayed repolarisation of Purkinje fibres
Prolonged repolarisation of mid-myocardial “M-cells”
After-potentials resulting from mechanical forces in the ventricular wall

Features of Normal U waves

The U wave normally goes in the same direction as the T wave
U -wave size is inversely proportional to heart rate: the U wave grows bigger as the heart rate slows down
U waves generally become visible when the heart rate falls below 65 bpm
The voltage of the U wave is normally < 25% of the T-wave voltage: disproportionally large U waves are abnormal
Maximum normal amplitude of the U wave is 1-2 mm

Delta Wave

Thu, 10 Feb 2022 00:00:00 +0000

Delta Wave Overview

The Delta wave is a slurred upstroke in the QRS complex. It relates to pre-excitation of the ventricles, and therefore often causes an associated shortening of the PR interval. It is most commonly associated with pre-excitation syndromes such as WPW.

The characteristic ECG findings in Wolff-Parkinson-White syndrome are:

Short PR interval (< 120ms)
Broad QRS (> 100ms)
A slurred upstroke to the QRS complex (the delta wave)

P wave

Sat, 29 Jan 2022 00:00:00 +0000

P Wave Overview

The P wave is the first positive deflection on the ECG and represents atrial depolarisation.

The P wave is the first positive deflection on the ECG
It represents atrial depolarisation
Normal duration: < 0.12 s (< 120ms or 3 small squares)

Characteristics of the Normal Sinus P Wave

Morphology

Smooth contour
Monophasic in lead II
Biphasic in V1

Axis

R wave

Thu, 04 Feb 2021 00:00:00 +0000

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R wave Overview

The R wave is the first upward deflection after the P wave. The R wave represents early ventricular depolarisation

Abnormalities of the R wave

There are three key R wave abnormalities:

Dominant R wave in V1
Dominant R wave in aVR
Poor R wave progression

1. Dominant R wave in V1

Causes of Dominant R wave in V1

Normal in children and young adults
Right Ventricular Hypertrophy (RVH)
- Pulmonary Embolus
- Persistence of infantile pattern
- Left to right shunt
Right Bundle Branch Block (RBBB)
Posterior Myocardial Infarction (ST elevation in Leads V7, V8, V9)
Wolff-Parkinson-White (WPW) Type A
Incorrect lead placement (e.g. V1 and V3 reversed)
Dextrocardia
Hypertrophic cardiomyopathy
Dystrophy
- Myotonic dystrophy
- Duchenne Muscular dystrophy

Ecg Waves on ECG Library – LITFL Basics

Osborn Wave (J Wave)

Osborn Wave (J Wave) Overview

Q Wave

The Q Wave

Q waves in context

Q waves in different leads

Pathological Q Waves

T wave

T wave Overview

Normal T wave characteristics

Peaked T waves

U Wave

U wave Overview

Source of the U wave

Features of Normal U waves

Delta Wave

Delta Wave Overview

P wave

P Wave Overview

Characteristics of the Normal Sinus P Wave

R wave

R wave Overview

Abnormalities of the R wave

1. Dominant R wave in V1

Causes of Dominant R wave in V1

Examples of Dominant R wave in V1

Normal paediatric ECG (2 yr old)