Lesson 6 Data Report ELECTROCARDIOGRAPHY II Bipolar Leads (Leads I, II, III) Einthoven s Law Mean Electrical Axis on the Frontal Plane

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1 Physiology Lessons for use with the Biopac Student Lab PC under Windows 98SE, Me, 2000 Pro or Macintosh Lesson 6 Data Report ELECTROCARDIOGRAPHY II Bipolar Leads (Leads I, II, III) Einthoven s Law Mean Electrical Axis on the Frontal Plane Manual Revision PL3.6.7-ML3.0.7/ Richard Pflanzer, Ph.D. Associate Professor Indiana University School of Medicine Purdue University School of Science William McMullen Vice President BIOPAC Systems, Inc. RA I + LA BIOPAC Systems, Inc. 42 Aero Camino, Goleta, CA (805) , Fax (805) info@biopac.com Web Site: LL

2 Page 2 Lesson 6: ECG II Biopac Student Lab Lesson 6 ELECTROCARDIOGRAPHY II Bipolar Leads (Leads 1, II, III), Einthoven s Law, and Mean Electrical Axis on the Frontal Plane Subject Profile DATA REPORT Student s Name: Lab Section: Date: Name Age Height Weight Gender: Male / Female I. DATA A. Direction of R waves for different leads Put a check in the column to indicate whether the R wave is positive + or negative for each Lead configuration: Table 6.1 R Wave Lead + I B. Mean Electrical Magnitude and Axis Graphical Estimate Use Table 6.2 to record measurements from the Data Analysis section: Table 6.2 CONDITION [CH 1] max QRS I [CH 3] max Lying Down Sitting Up Breathing In Breathing Out

3 Biopac Student Lab Lesson 6: ECG II Page 3 One way to approximate the mean electrical axis in the frontal plane is to plot the magnitude of the R-wave from and I, as shown in the Introduction (Fig. 6.4). 1. Draw a perpendicular line from the ends of the vectors (right angles to the axis of the Lead) using a protractor or right angle guide. 2. Determine the point of intersection of these two perpendicular lines. 3. Draw a new vector from point 0,0 to the point of intersection. The direction of this resulting vector approximates the mean electrical axis of the heart. The length of this vector approximates the mean potential of the heart. Create two plots on each of the following graphs, using data from Table 6.2. Use a different color pencil or pen for each plot. Graph 1: Lying down and Sitting Up 0, I From the above graph, find the following values: Condition Mean Electrical Magnitude Mean Electrical Axis Lying Down Sitting Up

4 Page 4 Lesson 6: ECG II Biopac Student Lab Explain the difference (if any) in Mean Electrical Magnitude and Axis under the two conditions: Graph 2: Breathing In /Breathing Out 0, I From the above graph, find the following values: Condition Mean Electrical Magnitude Mean Electrical Axis Breathing In Breathing Out Explain the difference (if any) in Mean Electrical Magnitude and Axis under the two conditions:

5 Biopac Student Lab Lesson 6: ECG II Page 5 C. Mean Electrical Axis and Magnitude More Accurate Approximation Add the Q, R, and S potentials to obtain net potentials. Lying down: Q R S I Q R S QRS Net 1 QRS Net 2 Graph 3: Lying Down 0, I From the above graph, find the following values: Condition Mean Electrical Magnitude Mean Electrical Axis Lying Down Explain the difference in Mean Electrical Magnitude and Axis for the Lying Down data in this plot (Graph 3) and the first plot (Graph 1).

6 Page 6 Lesson 6: ECG II Biopac Student Lab II. QUESTIONS D. Define ECG E. Define Einthoven s Law F. Define Einthoven s Triangle G. What factors affect the orientation of the Mean Electrical Axis? H. Refer to Table 6.2: How did the amplitudes of and I change between inhalation and exhalation? Did the heart s axis and magnitude change? I. What factors affect the amplitude of the R wave recorded on the different leads? J. Compare the mean electrical axis and magnitude obtained when i. using just the amplitude measurement of the R-wave vs. net potentials ii. lying down vs. sitting up End of Lesson 6 Data Report

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