Normally, cardiac impulses originate in the sinus node (located in the right atrium),

 it is then transmitted to all cardiac cells progressively (allowing them to contract in a precise order) by the myocardial cells themselves, from one atrium to the next, 

then through the electrical conduction pathways of the atrioventricular node (a kind of toll booth), which regulate the influx (sometimes slowing it down) and then convey it to the ventricles via the trunk of the His bundle and its right (for the right ventricle) and left (for the left ventricle) branches. 

The small fibers of the Purkinje network carry the impulse to the ends of the ventricles. 

 

A cardiac conduction disorder is a partial or total, transient or permanent interruption in the conduction of cardiac electrical impulses.

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Conduction blocks

Each interruption or slowing of the electrical impulse along its pathway can give rise to specific “conduction disorders”.

At the sinus node: sinus dysfunction, sinus pauses, sinus bradycardia

Between sinus node and atrial cells: Sino-atrial block, inter-atrial block ...

At the level of the atrio ventricular node: intra nodal atrio ventricular block

In the common trunk of the His bundle: Intra-Hissian atrio ventricular block

His bundle branches: 2 branches simultaneously (infra-Hissian atrio ventricular block) or left branch (left branch block or hemi block) or right branch (right branch block)

At ventricular cell level: intraventricular block

 

The severity, evolutionary potential and possible treatment depend on several parameters:

- the anatomical location of the block (sinus node? AV node? His node?)

- Whether or not it is complete (total interruption of the influx or slowing down?)

- the ability of other myocardial cells to take over (escape rhythm)

- the cause of the conduction block (permanent or transient? underlying heart disease? etc.)

- the ability of the heart and body to adapt to its new electrical conduction mode (what are the sym