# QRS complex

• Author
Posts
• #16885
ramichow
Participant

Why does the size and other features of the QRS complex vary according to the orientation of the electrodes?

one is positive(active) electrode in left leg , negative(reference) electrode in the left arm and the earthing in the Right arm.
second one is with positive(active) electrode in right arm, negative(reference) electrode in the left arm and the earthing in the left leg
the third one is with positive(active) electrode in right arm, negative(reference) electrode in the left leg and the earthing in the left arm.

• #113668
david23
Participant

remember your vectors back in physics. The heart is in a tilted position. the action potential moves accordingly.

• #113687
daniel.kurz
Participant

Go back to looking at physics of vectors of electrical charge. Vectors never cross and they are vectors that can be summed based on their components. If you think of the heart, electricity flows from the SA node, through the AV node, and then down the septum through the Bundle of His. As the electricity moves, the direction of flow at any given instant is defined by the vector. All the individual vectors from each cell of the heart are summed together to give the overall vector of the electrical flow. We see that on an EKG and talk about the QRS complex as a result. That is only made possible by the fact that an electrical engineer that made the EKG has cunningly made one recording lead the primary. When the vector is moving in that direction we see upwards direction movement on the EKG. When the vector is moving away we see downwards direction movement on the EKG. Assuming that the EKG recording leads were put on correctly.

In most cases, the heart is pointing down and to the anatomical left at an angle of about 5-10°. In rare cases, the heart can point to the anatomical right or in extremely rare cases can be inverted and pointing to the anatomical right.

• #115638
jamesfrank
Participant

In most cases, the heart is pointing down and to the anatomical left at an angle of about 5-10°. In rare cases, the heart can point to the anatomical right or in extremely rare cases can be inverted and pointing to the anatomical right.

• #115655
jamesfrank
Participant
quote jamesfrank:

In most cases, the heart is pointing down and to the anatomical left at an angle of about 5-10°. In rare cases, the heart can point to the anatomical right or in extremely rare cases can be inverted and pointing to the anatomical right.

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• #116113
leesajohnson
Participant

Normally, increased QRS indicates left ventricular hypertrophy. In technical parlance, the sum of the R wave in V5 or V6 and the S wave V1 is greater than 35 mill volts. But you are hardly 23 and since people within 40, if they are especially athletics or maintaining slim structure, it is common among them. Even it is normal with children and adolescents. So nothing to worry about this, as all other parameters is normal.
However, I suggest you to consult a Cardiologist good at his subject and who treated such patients too, since the reliability of high QRS by ECG alone without clinical diagnosis might be misled with false positive readings. http://www.healio.com/cardiology/learn- … rs-complex

• #116128
Frattoe
Participant

It has been a big struggle for me, too.
You have to imagine the ecg as a picture of heart axis referred to the direction of the segments linking electrodes. Just remember that you are spotting an electric wave moving across sensors, so what has to be positive and what to be negative is just a convention. Now imagine the diffusion of singal along the His bundle:each derivation shows the component of that diffusion related to the derivation’s orientation in the space. So q wave can be a little depression in curve, beeing that wave the septum activation, which is directed towards the right, thenthen you have q, directed upwards, representing lower ventricular activation, and than s, directed downwards, showing basal ventricular activation,if referred to an LS-P derivation. If you change the orientation of electrodes, the same electric movements will cause a different change in the polarity, and even the QRS complex will appear different, it is all a conventional question.