﻿ QRS Complex Morphologies

# QRS Complex Morphology

The QRS complex can present different morphologies, depending on the lead and the abnormalities present in the patient.

## QRS polarity: Positive, Negative or Biphasic?

QRS complex polarity is important in order to determine the QRS axis, when the QRS polarity in leads I and III allow us to quickly estimate whether it is normal or not.

Also, a predominantly negative QRS complex in precordial leads should spark a suspicion of abnormalities of the heart anterior wall.

But, when is a QRS complex positive or negative?

### Positive QRS Complex

When the amplitude of the largest positive wave (R or R') is larger than the amplitude of the deepest negative wave (Q or S).

### Negative QRS Complex

When the amplitude of the largest positive wave (R or R') is smaller than the amplitude of the deepest negative wave (Q or S).

### Biphasic QRS Complex

When the amplitudes of the largest positive and deepest negative waves are similar.

### Electrocardiographic meaning

When the QRS complex is clearly positive, it means that the electric impulse flows towards the lead; if the QRS complex is negative, the impulse flows away from the lead; if the QRS complex is biphasic it means the direction of the impulse is perpendicular to the lead.

## QRS Complex Morphology

Some authors prefer to differentiate the diverse QRS complex morphologies by using capital letters for waves with great amplitude and lower-case letters for those ones with small amplitude.

In certain articles of My EKG, we used this nomenclature for a better understanding, as we consider it an easy way to differentiate the multiple morphologies QRS can present.

Rs: tall R wave followed by a small S wave. On a normal electrocardiogram we find it in precordial leads V4-V6 and in all limb leads, except aVR.

qRs: small initial non-pathological Q wave, followed by a tall R wave and a small S wave. On a normal electrocardiogram, it can be seen in leads V5 and V6.

RS: tall R wave followed by a deep S wave, with similar amplitude (biphasic QRS). It is the characteristic morphology in lead sV3.

rS: small R wave followed by a deep S wave. Normal morphology in leads V1-V2.

In left posterior fascicular block it is seen in lateral leads; in left anterior fascicular block it is seen in inferior leads. It is commonly mistaken as a QS complex when the R wave is very small.

Qr: deep Q wave followed by a small R wave. Normal morphology in lead aVR. When found in other leads, it is a sign of myocardial infarction (previous STEMI) in the corresponding heart area.

QS: a lone, deep negative wave. It is a sign of myocardial infarction in the region near to the electrocardiogram leads, it should not be present on a normal EKG.

rSR': small R wave, followed by a deep S wave and a second tall R wave. It is a characteristic sign of right bundle branch block and incomplete right bundle branch block. It is also present in the Brugada syndrome.

Other morphologies: As you may well imagine, there are many more QRS complex morphologies. We have mentioned only the more frequent and important but we may also come across wide R waves, rSr’, QR, qR, qRS, qrS, among others.

In the next article we will further explain Posterior and Right-Side Leads. Click on Next down below to stay with us.

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