ECG AND HEART ECG AND HEART FUNCTIONFUNCTION

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ECG AND ECG AND EXERCISEXERCIS

EE Instructor Terry WisethInstructor Terry Wiseth

What Do I Need ToHand In For This Lab?

1) ECG Tracing Data Table At Rest

2) ECG Tracing Data Table After Exercise

3) Labeled Sketch of ECG Tracing At Rest

4) Labeled Sketch of ECG Tracing After Exercise

5) Answers to Questions 1-8

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You can use the links below to print off the data tables, graphs and questions you will need to hand in with this lab.

Questions 1-8Questions 1-8

ECG Tracing Graph PaperECG Tracing Graph Paper(You will want 2 copies of this)(You will want 2 copies of this)

ECG Data TableECG Data TableAt RestAt Rest

After ExerciseAfter Exercise

Click on the blackboard to view

a larger blackboard.

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DATA DATA ACQUISITION ACQUISITION UNITUNIT

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Monitor

ECG Sensor

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The electrocardiogram (ECG) can be monitored in the laboratory and gives information on the electrical activity of the atria and ventricles during the cardiac cycle.

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The cardiac cycle consists of a contraction of the atria and then the ventricles, followed by a period of rest. An impulse from the sinoatrial node produces a contraction of the atria and then excites the ventricles via the atrioventricular node.

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The currents produced by these impulses are recorded as the electrocardiogram or ECG, and the various waves can be correlated with the contractions of the atria and ventricles. An ECG is also called an EKG or electrokardiogram.

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We can summarize an ECG tracing in the image below. Each of the waves or spikes on the tracing can be represented with letters to indicate changes in electrical actions within the heart.

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It is easy to monitor a subjects electrocardiogram (ECG) in the lab and determine any changes provoked by exercise. In this lab the intervals between the various components of the ECG are measured from a volunteer at REST and immediately after EXERCISE, when the heart rate is elevated. The results will help to see how changes in physical activity affect heart function.

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Exercise increases the cardiac output by increasing 1) stroke volume and 2) heart rate. This lab compares the ECG from a volunteer at rest and during recovery from exercise. This is achieved by measuring the P-Q, Q-T and R-R time intervals and the QRS Complex amplitude to see which are affected by exercise. Study the image below to identify the various parts of the ECG tracing.

P

QS

T

R

PQ

QT

Atrial Contraction

Ventricular Contraction

QRS Complex Amplitude

Click on the Image or here to view a printable image

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The PQ Interval represents the atrial contraction. The length in time of the PQ interval can infer the strength of the atrial contraction. The QT Interval represents the contraction and relaxation of the ventricles. The length in time of the QT Interval can infer the strength of the ventricular contraciton.

P

QS

T

R

PQ

QT

Atrial Contraction

Ventricular Contraction

QRS Complex Amplitude

Click on the Image or here to view a printable image

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During exercise there is an increase in the amount of blood circulating around the body. Activation of the sympathetic nervous system increases cardiac output by modifying heart function in two ways:

1) The Stroke Volume Increases

2) The Heart Rate Increases

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1) The Stroke Volume Increases1) The Stroke Volume Increases

The volume of blood in the heart before contraction increases and the volume of the blood in the heart after contraction decreases. Thus the Stroke Volume (the amount of blood ejected from either ventricle during each cardiac cycle) increases because there is more blood in the ventricles before contraction and less remaining in the ventricles after contraction.

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Comparisons of Stroke Volumes can be inferred by the relative amplitude of the QRS complex of an ECG tracing at rest and after exercise.Amplitude is measured in millivolts (mV) and can be found on the vertical axis of the ECG tracing. A larger amplitude (mV) reading would indicate a more forceful ventricular contraction. A more forceful ventricular contraction causes more blood to be ejected during a cardiac cycle and thus an increased Stroke Volume.

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A measure of Stroke Volume can be inferred by the amplitude of the QRS complex of an ECG tracing.

sec sec sec

mV

Time

Amplitude

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2) The Heart Rate Increases2) The Heart Rate IncreasesThe number of cardiac cycles (contractions) per minute increases. The heart rate increase is a result of the excess CO2 produced by exercising muscles.

sec sec sec

mV

Time

AT RESTOne contraction each second

would represent a heart rate of 60 beats per minute

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ECGECG

sec sec sec

mV

Time

The image to the left is a tracing of an ECG reading. The spikes can be thought to represent one heart beat. From the tracing given here we can see that there is a spike every second.

Spikes

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ECGECG

sec sec sec

mV

Time

A spike each second would represent a heart rate of 60 beats per minute. As well, a spike every 0.5 seconds would represent a heart rate of 120 beats per minute.

Spikes

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During this experiment you will display an ECG from a volunteer at rest and during recovery from exercise. To Start click the Red power control button to turn on the Data Acquisition Unit.

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DATA DATA ACQUISITION ACQUISITION UNITUNIT

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StimulatorOutputs

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RecordingInputs

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Monitor

ECG Sensor

Start Recording Stop Recording

Timesec sec sec

mV

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ZOOM

PRINT

Click on the Blue lead from the ECG Sensor to plug it into Recording Input #1. The Red, Green and Black sensors on the table are radio telemetry sensors and will relay signals to the ECG Sensor.

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ZOOM

PRINT

Click on the Red electrode to connect it to the left wrist of the volunteer. Next click on the Green and Black electrodes to place them on the right foot and the right wrist respectively.

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DATA DATA ACQUISITION ACQUISITION UNITUNIT

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RecordingInputs

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Monitor

ECG Sensor

Start Recording Stop Recording

Timesec sec sec

mV

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PRINT

Start Recording the ECG waves by clicking on the Green button on the monitor. The ECG tracings will continue for about 40 seconds and will then stop. You should click on the Red button to stop recording.

Start Recording

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ECG Sensor

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Timesec sec sec

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At Rest

You should click on the STOP

RECORDING button at this time

ZOOM

PRINT

Start Recording Stop Recording

Timesec sec sec

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DATA DATA ACQUISITION ACQUISITION UNITUNIT

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ECG Sensor

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Click on the blue ZOOM button above to see a larger view of the ECG. Click on the yellow PRINT button view a printable version. Enter your data in the Data Table for At Rest.

P

QS

T

R

PQ

QT

Atrial Contraction

Ventricular Contraction

QRS Complex Amplitude

When you have collectedall of the data for the

subject at restClick Here to Go to the

Part 2 of the Lab

ZOOM

PRINT

We will now have the subject exercise by running in place for a prescribed period of time. Click on the subject above to begin exercising. When the exercise is completed we will monitor the ECG once again.

Start Recording

Monitor

Stop Recording

Timesec sec sec

mV

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DATA DATA ACQUISITION ACQUISITION UNITUNIT

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ECG Sensor

You will be notified what to do next, when the subject has exercised the prescribed time. Please be patient.

The exercise is now complete.Click Here to go to the

next slide to collect data

ZOOM

PRINT

Start Recording the ECG waves by clicking on the Green button on the monitor. The ECG tracings will continue for about 40 seconds and will then stop. You should click on the Red button to stop recording.

Start Recording

PowerPowerPowerPower

DATA DATA ACQUISITION ACQUISITION UNITUNIT

DATA DATA ACQUISITION ACQUISITION UNITUNIT

StimulatorOutputs

+

-

RecordingInputs

1

2

ECG Sensor

Monitor

Stop Recording

Timesec sec sec

mV

After Exercise

P

QS

T

R

PQ

QT

Atrial Contraction

Ventricular Contraction

QRS Complex Amplitude

You should click on the STOP

RECORDING button at this time

ZOOM

PRINT

PERFORM THE FOLLOWING SKETCHES

1)Sketch an image of the ECG tracing taken from the subject at Rest. Include at least three cycles in your sketch. Label the PQRST landmarks of one of the cycles.ECG TRACING PAPER

2) Sketch an image of the ECG tracing taken from the subject after Exercise. Include at least three cycles in your sketch. Label the PQRST landmarks of one of the cycles.ECG TRACING PAPER

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Click Here toView a Printable ECG

Graph Paper

Answer The Following Questions1) Which component of the ECG coincides with contraction of the

ventricles?

2) Which component of the ECG coincides with contraction of the atria?

3) What is the heart rate of the subject at rest?

4) What is the heart rate of the subject after exercise?

5) Describe at least two differences between the ECG tracings of the subject at rest and after exercise.

6) Why is the amplitude of the ECG tracing of the subject after exercise higher than when measured at rest?

7) Tachycardia is a term used to indicate a rapid heart rate. Which of the two ECG tracings performed indicate tachycardia?

8) Sinus rhythm is a term used to describe normal heart rate. Which of the two ECG tracings performed indicate sinus rhythm?

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of the Questions

1) ECG Tracing Data Table At Rest2) ECG Tracing Data Table After Exercise3) Labeled Sketch of ECG Tracing At Rest4) Labeled Sketch of ECG Tracing After Exercise5) Answers to Questions 1-8

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You have now collected the data you need to finish the lab. Be sure that you include the following in your lab report. You can click on each of the following to link to them.

Timesec sec sec

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Sketch the ECG tracing above. You can use the red link shown above to print out a blank ECG tracing graph. Using the time measuring bars and the mV scale on the left, find the time intervals for the following: R-R Interval, P-Q Interval, Q-T Interval, Amplitude of QRS Complex.

Click to ViewECG Data

Table at Rest

Click to View aPrintable Version

of this Image

Click Here toReturn to LastSlide Viewed

Click to View aPrintable Version

of blank ECGTracing Paper

After entering the data from the ECG tracing calculate the Heart Rate at REST by using the formula given in the table.

Click to View a PrintableVersion of the ECGData Table at Rest

ECG TracingsData Table at REST

 Time

seconds

Amplitude mV

Heart Rate HR = 60 / RR Interval  

RR Interval      

PQ Interval      

QT Interval      

QRS Amplitude      

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Sketch the ECG tracing above. You can use the link shown above to print out a blank ECG tracing graph. Using the time measuring bars and the mV scale on the left, find the time intervals for the following: R-R Interval, P-Q Interval, Q-T Interval, Amplitude of QRS Complex.

Click to ViewECG Data

Table AfterExercise

Click to View aPrintable Version

of this Image

Click Here toReturn to LastSlide Viewed

Timesec sec sec

Monitor

mV

1.0

0

0.5

1.5

Click to View aPrintable Version

of ECGTracing Paper

After entering the data from the ECG tracing calculate the Heart Rate after EXERCISE by using the formula given in the table.

Click to View a PrintableVersion of the ECG

Data Table After Exercise

ECG TracingsData Table After Exercise

 Time

seconds

Amplitude mV

Heart RateHR = 60 / RR Interval

RR Interval      

PQ Interval      

QT Interval      

QRS Amplitude      

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