A wider QRS indicates that conduction is occurring through an abnormal pathway. The wider QRS is indicative of the delay in conduction as it takes longer for electrical activity to travel from myocyte to myocyte compared to the electrical conducting system.

Which part of the conduction system is responsible for delay?

Atrioventricular Node

The AV node acts to delay the impulses by approximately 120ms, to ensure the atria have enough time to fully eject blood into the ventricles before ventricular systole.

Why is there a delay in conduction at the AV node?

In part, the slow conduction velocity of the AV node is the result of the small diameter of nodal myocytes (conduction velocity is function of cell diameter) and the complex arrangement of the myocytes (nodal myocytes can be separated by extensive connective tissue), which is expected to slow conduction, because the ...