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Bio212

Laboratory 3

The Electrocardiogram

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Objectives for Today’s Lab• Acquire a better understanding of the theory behind the

ECG

• Record and analyze an ECG• Computers set up in lab

• You will conduct the ECG on a lab partner

• Identify the components of a normal ECG

• Describe the phases of the cardiac cycle represented by each wave form on the ECG

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A GREAT Book on ECGs

This is you after reading the book…confident and no longer intimidated by ECGs!!

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Electrocardiogram

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Time

Mil

livo

lts

PR Interval: 0.12 – 0.20 sec

QT Interval: 0.20 – 0.40 sec

QRS Interval: < 0.10 sec

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The Bipolar Limb Leads

We will be using only Lead II today, so the right arm will be negative, and the foot will be considered positive

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The Electrocardiogram

A wave of the ECG will be positive (up) when the positive wave is moving toward the positive electrode

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Electrocardiogram and Heart Events

Recall that the left foot electrode is POSITIVE, so when the wave of depolarization is moving toward the left foot, we get a positive (up) deflection on the ECG

Right Arm(-)

Left Foot (+)

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Electrocardiogram and Heart Events

Right Arm (-)

Left Foot(+)

Remember that the T-wave represents repolarization of the ventricles.

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ECG Animation…

NYU ECG tutorial site…

This is available on Links to Explore for Lab 3

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The Paper Chart ECG

0.2 sec0.04 sec

Small boxes are usually 1 mm on each side

Ten mm high represents 1 mV

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The Paper ECG Chart

How long is the PR interval on this strip? The QT interval?

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Calculating the Heart Rate

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ECG Parameters

What you will be doing in lab today…

NOTE: This page is reproduced in your Laboratory Study Guide

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What you should do in lab today…

• Read the Background and Introduction in your PowerLab Teaching Experiment handout

• See the “Directions for Use of Laptop Computer” at your station if you laptop is not already turned on

• Set up as described in the demonstration – Use the chart at each ECG station for electrode placement

– Refer to Subject Preparation Steps 4-6 on page 3, if necessary for skin preparation and use of electrode gel

• Run the ECGs for each member of your group by following the Procedure in Exercise 1: ECG in a resting volunteer (page 5)

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What you should do in lab today…

• After EACH member of your group has an ECG recorded, be sure to SAVE the ECG into a file!!!– Select File | Save As (to prevent overwriting

someone else’s file with your data)– Enter a file name using your first and last name

with no spaces as the file name, e.g., SueCidal). – File is saved to the Desktop, so when you retrieve

it later to analyze the data , LOOK ON THE DESKTOP!

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What you should do in lab today…

• After all members of your group have had an ECG recorded…– Analyze your own ECG (use the laptop software)

• Determine the heart rate for your ECG• Examine the PR interval, QRS interval, and QT

interval in your ECG and determine if these are within the normal range

– Complete Part A, C, and D #3-6 and the Critical Thinking Application of your Laboratory Report and hand in with your ECG. Be sure your name is on all the sheets you hand in.

• Before you leave, please delete your ECG file from the Desktop