The movement of electrical signals across the heart is what is traced on anelectrocardiogram(EKG).
This article explains five components of the cardiac conduction system and how they work.
It also discusses howheart diseaseor aheart attackcan cause serious disruptions in the system.
Illustration by Mira Norian for Verywell Health
Where Do Electrical Impulses Start in the Heart?
The heart generates its own electrical signal.
The cardiac electrical signal controls the heartbeat in two ways.
Illustration by Mira Norian for Verywell Health
First, since each electrical impulse generates one heartbeat, the number of electrical impulses determines theheart rate.
In a normal sinus rhythm, that rate will be between 60 and 100 beats per minute.
The sinus node signal also controls electrical conduction as it “spreads” across the heart.
Illustration by Mira Norian for Verywell Health
For this reason, the sinus node is often referred to as the heart’s “natural pacemaker.”
you’re able to see the two atria and the two ventricles.
Separating them is a layer of fibrous tissue, labeled the AV disc.
Illustration by Mira Norian for Verywell Health
This tissue keeps the electrical signal passing through the AV node.
This is shown by the solid red line on the EKG in this figure.
As the electrical signal travels through the ventricles, it generates the QRS complex on the EKG.
Illustration by Mira Norian for Verywell Health
(The QRS complex is indicated by the solid red line on the EKG to the left.)
This interference prevents the atria from telling the ventricles when to contract and pump blood.
In most cases of heart block, the electrical signals are weakened but do not stop completely.
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Bundle branch block by itself often does not require treatment.
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