Why is the QRS complex wider in VTach? Since it represents ventricular depolarization, and the ventricles are tachycardic, shouldn’t the QRS complex be narrower?
In: Biology
QRS duration has more to do with how the electrical impulse is conducted. If it goes through the his purkinje system, it will be narrow, otherwise it will be wide.
Think of the HPS as a railroad for electrical impulse, transmitting electrical signal to each cell quickly and efficiently. The backup system is that each heart cell can transmit signal from cell to cell instead of via the railroad. Think instead of railroad, you have spread of electrical signal by word of mouth, this will make it longer in onset before the whole ventricle depolarizes, which will appear as a longer duration of your QRS.
In VTach, the QRS is wide bc each beats conduction is being passed on by word of mouth, cell to cell. However it is still a fast rate because each individual electrical impulse wave is faster.
Take separately, any supraventricular tachycardia, where the impulses travel through the AV node, which acts as a rail station, slowing down electrical signals, then translating them on down through the HPS, you get narrow, fast beats. If any SVT found a bypass tract around the AV node, then suddenly you have something called SVT with aberrancy, which means that the rate of the heart beats are from above the AV node, but the QRS is wide because it is being conducted through an aberrant conduction pathway, not through the AV node.
The other way to get aberrant or wide QRS is blockage in the HPS, like Left bundle branch block or right bundle branch block, in which a piece of the train tracks are blocked, and therefore word of mouth spread takes place to communicate the electrical impulse.
So overall, wideness of the QRS is based on how electrical impulses are being communicated regardless of the rate of the electrical impulses.
It has to do with point where the depolarization starts, when the standard beat starts above the ventricles of the heart it goes through the conduction system within the heart. In ventricular tachycardia it is starting somewhere in the ventrical and not following the normal electrical pathway and takes longer to depolarize giving you the widened QRS.
Can I get a ELI5 for this ELI5?
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