ECG Waves

The ECG waves section covers the basics of all the physiologic and pathologic waves seen on an ECG and rhythm strips.

P wave

Normal Morphology

Q wave

Normal Morphology
Pathologic Q waves

R wave

Normal Morphology
R wave peak time (RWPT)
Poor R wave Progression (PRWP)

S wave

Normal Morphology

T wave

Normal T wave Morphology
Abnormal T waves

U wave

– Small deflection following T wave, represents repolarization of Purkinje fibers
– Amplitude: 0.5 mm, same direction as T wave
– Best seen in lead V2 and V3
– U wave size increases with slow heart rate and decreases with fast heart rate
– Most commonly seen when HR < 65 BPM
– Amplitude of U wave is < 25% of the T-wave
– Prominent U waves are seen in hypokalemia. Can also be seen in bradycardia, ventricular hypertrophy, hypothyroidism, electrolyte changes etc.
– Negative U wave can sometimes be seen in early myocardial ischemia
Source: Papp C. Br Heart J 1940;2:9ñ24.

Osborn wave (J wave)

– A subtle positive defection at the J point (end of QRS complex)
– It is negative in lead aVR and V1
– Best seen in inferior and lateral leads
– Usually caused by hypothermia
– Size of Osborn wave correlates with degree of hypotheria

Epsilon wave

– Small blip like deflection seen at the end of QRS complex
– Best seen in lead V1 and V2, can extend till V4
– Cause: post-excitation of myocytes in the right ventricle
– Commonly seen in arrhythmogenic right ventricular dysplasia (ARVD)

Delta Wave

– Slow, slurred upstroke of the QRS complex
– Seen with short PR interval of < 120ms
– Broad QRS (> 100ms)
– Commonly associated with pre-excitation syndrome such as Wolff-Parkinson-White syndrome (WPW)

Benign Early Repolarisation

– Concave ST elevations with elevation J point
– Notched and elevated J point
> Type 1 – BER pattern seen in lateral precordial leads. Low risk of arrhythmic events.
> Type 2 – BER pattern seen in inferior or inferolateral leads. Moderate risk of arrhythmic events.
> Type 3 – BER pattern seen globally (inferior, lateral, right precordial leads), associated with VFib/ VT

De Winter T waves

– Characterized by 1-3 mm of ST-depression with upright, tall, prominent symmetrical T-waves
– Seen in precordial leads
– Subtle reciprocal ST segment elevation (> 0.5 mm) in aVR
– Usually seen in proximal LAD occlusion