#4 Cardiovascular I The Heart & EKG

Transcription

1 #4 Cardiovascular I Objectives: Identify a list of human heart structures using a virtual human dissection Dissect a sheep heart to identify external and internal structures Identify a list of human heart structures on a model Perform an EKG under different conditions (lying down, sitting up, deep breathing) Understand the parts of the EKG Analyze the duration of the EKG waves Equipment: Remember to bring gloves, goggles, dissecting kit, appropriate shoes, photographic atlas. Figure 1. Structures of the human heart Prelab Activity: Create hypotheses for the EKG experiments by filling in the following sentences (use: go up, go down, or stay the same). A. The heart rate (BPM) sitting up will compared to lying down. B. As heart rate (BMP) goes up, deltat (pg 9, Fig 8) will. C. The time for the p-wave while lying down will compared to sitting up. D. The heart rate (BPM) during inhaling will compared to exhaling. I. Introduction The heart has four chambers two upper atria (singular, atrium) and two lower ventricles. Blood enters the atria from the large veins and passes into the ventricles before being ejected from the heart within the large arteries to either the lungs or the rest of the body (Fig. 1). II. Virtual Human Heart Examination Preparation 1. Start the Anatomy & Physiology Revealed software by double clicking the icon. 2. On the home screen, from Module (top center) select Cardiovascular from the drop down Menu. 3. From the icon list at the top center, click the left most icon (the dissection icon). Page1

2 4. Under the Structure List column (top left) use the Topic drop down menu to choose Thorax. 5. From the View drop down menu choose Arteriesanterior. Do not select a Structure Type at this point. 6. At the bottom of the left column are the layer tools. Move the red arrows down to gradually remove each layer of the body. The layers must be removed in order. Remove Layers 1 and 2 to visualize the pericardium in Layer To identify visible structures within a layer, click on the radio button at the top of the layer that is on display. Pins will appear marking labeled structures. 8. Hover over a pin and the name of the structure will appear. Or click on a pin and the structure will be highlighted in the main view and further information on the structure will appear in the various boxes in the left column. Another identification method is to click on the name of the structure in the information section. 9. Practice using the layer tools and highlighting structures by clicking on the pin or name. III. Virtual Human Heart Examination Cardiovascular system, thorax, arteries-anterior, dissection layer 3 Structures AP Revealed 1. pericardium (also known as pericardial sac) 1. The introductory instructions on page 2 will bring you to this view (APR Fig. 1). 2. Note the position of the heart within the thoracic cavity. 3. The heart is enclosed in the double-layered pericardium (APR Fig. 1). 1 APR Fig.1 Page2

3 Cardiovascular system, thorax, arteries-anterior, dissection layer 4 Structures AP Revealed 2. heart 3. aorta a. aortic arch b. brachiocephalic artery c. left common carotid artery d. left subclavian artery 4. pulmonary trunk 5. vena cava a. superior b. inferior (not shown) 1. Use the layer tool to move one layer deeper (Layer 4). The pericardium is removed in this layer revealing the major vessels associated with the 5 heart (APR Fig. 2). a 2. Use the labeling pins to locate 3 4 the aorta (3), superior vena cava (5a), and pulmonary 2 trunk (4). 3. Note: the vessels branching from the aorta are labeled in APR Fig 3. APR Fig. 2 Cardiovascular system, thorax, arteries-anterior, dissection layer 5 Structures AP Revealed 3. aorta a. aortic arch b. brachiocephalic artery c. left common carotid artery d. left subclavian artery 1. Use the layer tool to move to Layer 5 (APR Fig. 3). 2. The anterior veins have been removed to reveal the arteries branching from the aortic arch. 3. Locate the aorta arch (3a), brachiocephalic (3b), left common carotid (3c), and left subclavian (3d) a. 3b 23c 3 a 3d APR Fig. 3 Cardiovascular system, heart, vasculature-anterior, dissection layer 2 Structures AP Revealed 6. coronary arteries a. right b. left 7. pulmonary arteries (not shown in this view) 8. right and left pulmonary veins (right shown in this view) 1. To see the heart details, choose Heart from the Topic drop down menu in the left column. Choose Vasculature-anterior under the View menu. Move to Layer 2 (APR Fig. 4). 2. Use the labeling pins for all three layers to locate the structures on the left. Also shown in this view are the cut end of the superior and inferior vena cavae (5a,b). 8 5a 5b 6a APR Fig. 4 6b Page3

4 Cardiovascular system, heart, internal features-anterior, dissection layer 1 Structures AP Revealed 9. auricle a. right b. left 10. ventricle a. right b. left 11. apex 1. Choose Heart from the Topic menu and Internal featuresanterior from the View menu (APR Fig. 5). 2. Use the labeling pins to locate the structures on the left 9a 9b 10a 10b 11 APR Fig.5 Cardiovascular system, heart, internal features-anterior, dissection layer 5 Structures AP Revealed 12. atrium (atria, pl.) a. right b. left 13. interventricular septum 14. atrioventricular valve a. right (tricuspid) b. left (bicuspid) 15. papillary muscle 16. chordae tendineae 17. semilunar valve a. pulmonary (not visible in this figure) b. aortic III. Sheep Heart Dissection 1. Move to Layer 5 (APR Fig. 6). 2. In this view, move up and down through Layers 2-6 to find the appropriate labeling pins for the structures on the left. APR Fig. 6 A. Preparation 1. Wear goggles, gloves, and an apron for the entire time that you are working with preserved specimens. 2. Obtain a dissecting tray and a sheep heart. B. Exterior Observations 17b 12a 14a 12b 14b auricles (right and left) ventricles (right and left) apex pulmonary trunk aorta Page4

5 Use your atlas to orient the heart. The prominent features on the anterior surface are the left auricle and the pulmonary trunk. Most of the vessels will emerge on the posterior surface, however, they might have been cut close to the heart and only the openings will be visible. The apex is composed of the left ventricle. *Check with your instructor that you have the heart correctly oriented before you cut the heart. C. Interior Observations atria (right and left) ventricles (right and left) interventricular septum atrioventricular valves tricuspid (right) bicuspid/mitral (left) FRONTAL SECTION: semilunar valves aortic pulmonary chordae tendineae papillary muscle 1. *Make sure to be very careful with your scalpel. Never cut towards your body or hands / fingers. Be very careful also when cleaning the scalpel. Never touch the blade or move it near you or others. 2. To start, place the heart flat on the dissection pan with the apex towards you and the base away from you. Do NOT hold the heart in your hand. 3. Keep the heart steady by placing the flat of your palm (the hand without the scalpel) on the anterior surface of the heart with your finger-tips raised off of the heart s surface. Your scalpel should never be near your hand or fingers. You are cutting on the plane between the bench and your hand. 4. Cut the heart first from base to apex. Make a frontal section with your scalpel by cutting through the center of the auricle toward the apex. Turn the heart so that the apex is at the top and continue the cut through the apex and down through the opposite auricle. If needed, finish the cut through the interventricular septum and base to cut the heart completely into two halves. Note that the heart is asymmetrical. The left ventricle makes up apex, is the largest chamber of the heart with the thickest wall. The interventricular septum separates the two ventricles. The right ventricle is slightly posterior to the left ventricle and much smaller. Locate the atrioventricular valves between the atria and ventricles. The chordae tendineae are attached to the inferior aspect of the valves. Papillary muscles bind the chordae tendineae to the ventricle walls. The aortic and pulmonary semilunar valves are at the junction of the ventricles with the aorta and pulmonary trunk, respectively. Confirm the location of each vessel by inserting a blunt probe through the atria. Find all the structures on your Interior Observation list. Page5

6 D. Directions for Cleaning Up 1. All specimen tissue should be thrown away as directed by your instructor. Please do NOT allow tissue to end up in the sink. It will clog the drain and cause extra work for lab assistants. 2. Thoroughly wash your dissecting tray with soap and water, dry, and return it to the lab bench where you found it. 3. Carefully clean your dissecting tools keeping the scalpel blade away- from your skin. 4. Use the spray disinfectant cleaner provided to thoroughly wipe down your lab bench area so that it will be ready for the next group of students. 5. Dispose of your gloves, paper towels and old plastic bags in the regular trash containers, NOT the red biohazard containers. 6. Make sure that you take your dissecting kit and goggles with you when you leave the lab. IV. Human Heart Model Observation Locate the following structures on the human heart model: aorta brachiocephalic artery left common carotid artery left subclavian artery pulmonary trunk vena cava superior inferior auricle right left ventricle right left apex pulmonary arteries pulmonary veins atria right left interventricular septum atrioventricular valve right (tricuspid) left (bicuspid or mitral) papillary muscle chordae tendineae semilunar valve pulmonary aortic V. EKG using BIOPAC Figure 2. The EKG waveform. The electrocardiograph (ECG or more commonly known as EKG) measures the electrical activity of the heart. The waveforms represent the electrical activity of the heart which occurs just prior to the contraction / relaxation of the cardiac muscle. The P-wave represents the depolarization of the atria just prior to atrial systole (contraction), QRS complex the depolarization of the ventricles, and the T-wave repolarization of the ventricles (Figure 2). The repolarization of the atria is obscured by the electrical activity of the ventricles. Electrodes or leads are placed on the skin in a pattern. Several lead patterns can be used including a 12, 5, and 3 lead placement. Figure 3 indicates the placement of the electrodes for a Page6

7 three (3) lead EKG. We will measure our EKG while lying down, sitting quietly, and after exercise. FOLLOW the directions below carefully. BIOPAC Equipment Setup: 1. The BIOPAC MP45 unit will already be plugged into the computer and attached to the electrodes (Channel 1). 2. Log on to the computer using your login so that you may print your results at the end. 3. Start the BIOPAC Student Lab program by finding the icon on the desktop and double-clicking it. 4. Select the lesson: L05 - (ECG) I (click OK). 5. Type in a name for the file you will recognize (ie. the subject s name) (click OK). Subject Preparation: 1. Place the leads on the subject as shown in Figure 3. Make sure that the flat side with the metal is against the skin and that the cords are not twisted. The leg leads should be placed on the medial surface of the leg just above the ankle. The arm lead should be placed on the forearm just above the wrist. Remove jewelry as it may cause recording errors. 2. The subject should lie quietly on the mat and avoid moving or talking during calibration and data collection. *Note: You will perform ALL the recordings first and then proceed to analyze the data. Calibration: 1. When the equipment is ready and subject is still, click Calibrate (upper left). It will stop automatically at 8 seconds. Figure 3. Electrode (lead) placement for the EKG. 2. Observe the calibration data recorded on the screen. Figure 4. Calibration screen. It should look similar to Figure 4, and if so, Continue to the next section. If the data do not appear similar, click Redo Calibration. Lying Down (Supine) 1. When the subject is still, click Record and collect data for 20 more seconds. The time in seconds passes on the bottom. Page7

8 2. Click Suspend when the time reaches 28 seconds. 3. The data should appear similar to the calibration. If so, click Continue to go to Sitting up. If the data appear abnormal, click Redo when the subject is ready and repeat steps 2 & 3. Sitting up with normal breathing 1. Next have the subject sit on a chair. The subject must remain still (movements of the arms and legs may cause unwanted changes in the recording). 2. When the subject is sitting in the chair and still, click Record and collect data for 20 more seconds. The time in seconds passes on the bottom. 3. Click Suspend when the time reaches 48 seconds. 4. The data should still appear regular and similar to the calibration recording. If so, click Continue to go to Deep Breathing. If the data appear abnormal, click Redo when the subject is ready and repeat steps 2-4. Deep Breathing 1.Be ready to take 5 slow deep breaths. You will note the inhale start by clicking F4 and the exhale start by clicking F5. 2. Click Continue to start collecting data for 5 slow deep breaths. F4 inhale start F5 exhale start 3. Click Suspend when all five breaths are completed. 4. The data should still appear regular and similar to the calibration recording, If so, click Done and remove the electrodes. If the data appear abnormal, click Redo (upper left) when the subject is ready and repeat steps 1-4. After you click, Done, a window will pop-up. Click, yes to save the data. To continue to data analysis, click, Analyze current data file. Data Analysis Preparing the Data 1. In the far right side of the recording window, are the tools you will use to help analyze your data (Figure 5). Figure 5. Data analysis tools. Page8

9 2. The time in seconds is shown on the scroll bar at the bottom of the recording window. Go to the 8-28 second recording segment where the subject was lying down (Figure 6). Figure 6. Diagram of recording segments. 3. Using the magnifying tool, click on the first waves that were produced until you can see only about 5-8 wave patterns. The data will at this point appear strange - follow step At the top of the screen, select the Display menu and then click on Autoscale Waveforms (top left). Repeat magnify and Figure 7. Data analysis screen. Autoscale waveforms until the data appears similar to Figure 7. If you need to go back, click, Display, and then zoom previous to undo your previous zoom or Display, autoscale horizontal to see the whole data set again to start the procedure over again. Analysis: Lying down (Supine) Heart Rate Figure 8. R-R measurement. 1. Using the I-beam tool, select one waveform to measure. Click and drag from one peak (R) to the next peak (R) to select this interval (see Figure 8). This is called the R- R value and represents the time between heart beats (deltat) and the computer will calculate the heart rate (BPM). Page9

10 2. In Table 1, record the measurements for deltat and BPM from the corresponding boxes at the top of the screen. This is sample 1. Repeat this process for one more waveform, recording the value in Table 1. Round each number off to the nearest 0.01 place. Analysis: Components of the EKG 1. Using the I-beam tool, select each component of the EKG waveform: P- wave (Figure 9), QRS complex (Figure 10), and T-wave (Figure 11) individually in sequence, and record their durations (deltat) as waveform 1 in Table 1. Repeat for one more waveform. The waveforms chosen may be the same as in the R-R measurements. Again, round off to the nearest Figure 9. P-wave selection. Figure 10. QRS complex selection. Figure 11. T-wave selection. Page10

11 Analysis: Sitting up Use the scroll bar at the bottom of the recording window (see Figure 12), to go to the recording segment when the subject was Sitting Up (28-48 seconds). A black vertical bar denotes where a new recording starts (Figure 12). Repeat the procedures to measure heart rate, duration, and EKG components as for Lying down. Record your measurements in Table 2. Analysis: Deep Breathing Use the scroll bar at the bottom of the recording window, to go to the recording segment Deep Breathing (48-about 108 seconds, Figure 12). A black vertical bar denotes where a new recording starts (Figure 12). Repeat the above procedures to measure heart rate (BPM) and duration (deltat) only following the directions below: *Make only one EKG measurement for each inhale and exhale segment giving a total of 4 EKG measurements inhaling and 4 for exhaling. You will not need to use one of the segments if you recorded 5 breaths. The beginning / end of each segment is marked by small triangles at the top (Figure 12 arrows at top). Scroll to find the next triangle showing the start of the next segment. Record your measurements (to the nearest 0.01) in Table 3. Print a copy of your last recording screen (Deep Breathing) for each member of your group. Click: Print, Preferences, Landscape (leave the setting on Visible Only). Label one heart beat on your EKG as shown in Figure 2 and attach to your lab report. When Finished, click File and then Quit to exit the program. Figure 12. Deep Breathing segment The first Inhale segment New recording segment beginning Scroll bar Page11

12 Cardiovascular I The Heart Name: Laboratory #4 Report For each label in the human heart figure above, give the name of the structure on the correct line below. A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. Page12

13 Cardiovascular I The Heart Name: Part V. EKG using BIOPAC Table 1. Lying Down / Supine Heart rate and duration. Measurement waveform 1 waveform 2 Average Duration (R-R) Heart rate (BPM) Components of the EKG Measurement waveform 1 waveform 2 Average P-wave QRS complex T-wave Table 2. Sitting Up Heart rate and duration. Measurement waveform 1 waveform 2 Average Duration (R-R) Heart rate (BPM) Components of the EKG Measurement waveform 1 waveform 2 Average P-wave QRS complex T-wave Page13

14 Cardiovascular I The Heart Name: Table 3. Deep Breathing Heart rate and duration. Measurement Inhale 1 Inhale 2 Inhale 3 Inhale4 Average Duration (R-R) Heart rate (BPM) Exhale 1 Exhale 1 Exhale 1 Exhale 1 Average Duration (R-R) Heart rate (BPM) A. EKG Questions 1. Under which condition (1 or 2) was the pulse rate slowest? 2. Is this what you hypothesized? 3. Was your hypothesis about deep breathing correct? 4. What does the p-wave represent? 5. Does the duration (deltat) of the p-wave change much? B. Look up the following: 4. What is an arrhythmia? 5. Atrial flutter: 6. Ventricular fibrillation: 7. Long QT syndrome (LQTS): 8. Which of the above arrhythmias is depicted in B? Page14