The Electrical Conduction System Advanced Cardiac Care in the Streets Understanding EKGs Ray Taylor Valencia College The Electrical Conduction System

Notice All rights reserved. Slide show used with permission only for the purposes of educating emergency medical providers (EMTs and Paramedics) No portion of this presentation may be reproduced, stored in a retrieval system in any form or by any means (including but not limited to electronic, mechanical, photocopying etc.) without prior written permission from the author

The Electrical Conduction System Objectives 1. Identify the location and function of the following: SA Node Internodal pathways Bachmann’s Bundle AV Node Bundle of His AV Junction Bundle Branches Purkinje Network

The Electrical Conduction System Objectives 2. Relate the normal path of an impulse traveling through the heart’s electrical conduction system

Cardiac Conduction System Components Sinoatrial Node Internodal Atrial Pathways Bachman’s Bundle Atrioventricular Node Atrioventricular Junction Bundle of His Left and Right Bundle Branches Purkinje Fibers

The SA Node The Sinoatrial [SA] Node is located in the upper posterior portion of the right atrial wall of the heart Junction of RA and SVC “primary pacemaker” of the heart Firing rate = 60 to 100 beats per min. Depolarization and Myocardial contraction occurs after impulse leaves SA Node

Internodal Pathways The Internodal pathways receive the electrical impulse as it exits the SA Node. Anterior, posterior, and middle pathways Pathways distribute impulse throughout atria Transmit impulse from SA Node to AV Node

Bachmann’s Bundle Bachmann’s Bundle - a group of interatrial fibers contained in left atrium A subdivision of anterior internodal tract Conducts electrical activity from the SA Node to the left atrium

The AV Node The Atrioventricular (AV) Node - located on floor of right atrium above tricuspid valve Electrical activity delayed 0.05 seconds Allows for more complete filling of ventricles Only pathway for atrial electrical impulses to reach ventricles “Gate-Keeper to the ventricles

The AV Junction The AV Junction is where SA Node joins Bundle of His SA Node fails or slows below normal, AV junctional tissues initiate electrical activity Secondary (escape) Pacemaker Discharges at intrinsic firing rate 40 – 60 beats per minute

The Bundle of His Bundle of His - conduction pathway that leads out of AV node Lies at top of interventricular septum Referred to as the “common bundle” Makes electrical connection between atria and ventricles Ability to self-initiate electrical activity at intrinsic firing rate of 40 to 60 beats per min.

Bundle Branches Bundle of His divides into two main Bundle Branches 1. Right Bundle Branch Long and thin Extends to apex of right ventricle 2. Left Bundle Branch Anterior and posterior fascicles Conduct electrical activity from Bundle of His to Purkinje Network

Purkinje’s Network Purkinje’s Network - fibers that spread throughout the ventricles Carries impulses directly to ventricular muscle cells Intrinsic firing rate of 20 to 40 beats per min.

Summary of Conduction System SA node Internodal pathways and Bachman’s bundle AV Node His Bundle Bundle Branches Purkinje Network

Summary of Discharge Rates Sinoatrial Node Primary pacemaker with fastest intrinsic discharge rate 60 – 100 beats per minute AV Junction Secondary pacemaker 40 – 60 beats per minute Purkinje Fibers 20 – 40 beats per minute

Thank you!