W03 worksheet

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W03 Worksheet: EKG, Pulses, & Blood Pressure Follow the instructions below very carefully. Many of the items in this assignment require reading, or videos, or something else to do. Each question has either a text box that can be filled out or a box that can be checked to show completion. Be sure to type out your answers completely and expand the text boxes if you need the additional space. Question 1 --- 4 points EKG The electrocardiogram (ECG or EKG) is the standard clinical tool used to measure the electrical activity of the heart. Data obtained from an EKG provides a graphical representation of the rate, rhythm, and pattern of electrical signals produced by action potentials traveling through cardiac myocytes. Recall that in a cell at rest, the inside of the cell has a negative charge with respect to the outside. That charge reverses when an excitable tissue such as a cardiac muscle cell depolarizes during an action potential. If one group of cardiac myocytes is depolarized (positive inside and negative outside) while another group is at rest (negative inside and positive outside), we have perfect conditions to generate an electrical current. If these oppositely charged areas are then connected by some sort of a conductor, an electrical current will flow. In our bodies, the extracellular fluid acts as a conductor allowing current to flow around the heart. Electrodes placed at strategic locations can then detect that current. By attaching electrodes to a galvanometer, tracings can be recorded that give us information about the magnitude and direction of the currents. Furthermore, by placing the positive and negative electrodes at different locations on the body, the EKG will give different “views” of the electrical activity. Each unique positioning of the electrodes is referred to as a lead. For example, in lead I the positive electrode is placed on near the left arm, and the negative electrode is placed near the right arm. For lead II, the positive electrode is placed on near the left leg, and the negative electrode near the right arm. By placing the electrodes in different positions, a total of 12 standard leads can be obtained, six limb leads, and six chest leads, giving 12 unique views of the electrical activity of the heart. Watch the video, “ Electrical system of the heart ” (links to an external site) ( 9:42 mins; Electrical Systems of the Heart Transcript ) to learn about the electrical activity of the heart (about 10 minutes). This EKG Explained (links to an external site) video will explain the ECG waves ( 17:26 mins; EKG Explained Transcript (links to an external site). You can view the animation of the EKG Explained (links to an external site) here.

Describe in your own words what each wave form means on a standard EKG tracing. Your answer: During the P wave, the atrium contracts to push the last 20% of blood into the ventricles. The SA node is the reason for this contraction. The SA node tells the atrium to contract using an electrical signal. During the QRS complex, all valves are closed. The ventricle is full of blood, and the ventricles contract. The AV node sends an electrical signal, and this is the reason for the ventricular contraction. During this time the atrium is relaxing. During the T wave, the ventricles relax. Most of the blood has exited the heart through the semilunar valves. At the end of the T wave, all valves are closed and the atrium is refilling. Question 2 --- 2 points Einthoven’s Triangle Image above is downloaded from Wikicommons November 2013. Title: Einthoven Triangle; Author: Kychot; License: Creative Commons Attribution-Share Alike 3.0 Unported

Einthoven's triangle is a standard bipolar 3 lead setup for an ECG tracing. By convention, lead I has the positive electrode on the left arm, and the negative electrode on the right arm, and therefore measures the potential difference between the two arms. In the lead II configuration, the positive electrode is on the left leg and the negative electrode is on the right arm. Lead III has the positive electrode on the left leg and the negative electrode on the left arm. These three leads form a triangle (with the heart at the center). This is often referred to as Einthoven's triangle, in honor of Willem Einthoven who developed the electrocardiogram in 1901. It does not matter if the leads are attached to the trunk or the end of the limb (wrists and ankles) because the limb can simply be viewed as a conductor “like a wire” originating from a point on the trunk of the body. Watch Einthoven’s Triangle (links to an external site), which will explain Einthoven’s Triangle and a standard 3-Lead ECG setup further ( 8:26 mins; Einthoven's Triangle Transcript ). If you are attending the campus lab, you will be given instructions on how to use our equipment to set up a 3-lead ECG test and perform it. Research answers for the following questions: Explain what a PR interval is, and also explain what might cause it to change. (Be detailed. Explain the mechanisms that cause the change, and don’t just list situations that can cause change.) Your answer: The PR interval is the period of time from atrial depolarization to ventricular depolarization. During this interval, the atrium contracts and fills the ventricles the rest of the way with blood. Next, the AV valve closes and the ventricles are filled with blood. The ventricular volume is at its peak. A faulty AV valve could cause change to this process. If the AV valve does not close all of the way, the blood will leak back into the atrium and the ventricular pressure will never be as high as it could with a normally functioning AV valve. The sympathetic system could affect the PR wave by speeding up the process. When the heart rate speeds up, the SA node and AV node are firing faster.

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Question 3 --- 2 points Explain what a QRS interval is. Also explain what might cause it to change. (Be detailed. Explain the mechanisms that cause the change, and don’t just list situations that can cause change.) Your answer: The QRS interval is the point of ventricular depolarization and contraction. The first part of this phase is the closing of the AV valve. When the AV valve shuts, there are no valves open and the ventricle is full of blood. The ventricles contract and the semilunar valves open. Increased levels of epinephrine and norepinephrine can lower the span of time that the QRS complex takes place. This is because the sympathetic system speeds heart rate. Question 4 --- 2 points Explain what a QT interval is, and also explain what might cause it to change. (Be detailed. Explain the mechanisms that cause the change, and don’t just list situations that can cause change.) Your answer: The QT wave is from the point of ventricular depolarization and contraction to ventricular repolarization and relaxation. At the beginning of this phase, all valves are closed and the ventricle is filled with blood. Then, the ventricle contracts and the semilunar valves open. The blood is ejected out of the ventricles through the semilunar valve. As the blood leaves the ventricles, the ventricular volume decreases, as well as the ventricular pressure. Once all the blood has exited the ventricles, the semilunar valves shut. The closing of these valves is the second heart sound. At this point the ventricles are relaxed. If there is a faulty semilunar valve, the blood being ejected could leak back into the ventricle. This would also lower the force of contraction because if the semilunar valve is leaky the blood would start leaving the ventricle before it is supposed to. Question 5 --- 2 points Explain what an ST segment is, and also explain what might cause it to change. (Be detailed. Explain the mechanisms that cause the change, and don’t just list situations that can cause change.)

Your answer: The ST interval represents the ejection of blood from the ventricles. The AV valves are shut and the ventricles are filled with blood. The semilunar valve is open and blood is ejecting out of the ventricles. Eventually ventricular pressure decreases and the blood is emptied out of the ventricles. The semilunar valve shuts and the ventricles are relaxed. The force of contraction can be weak due to a number of different factors (dehydration, diabetes, pregnancy, medication, etc). If the force of contraction is weak, all of the blood might not be able to eject from the heart before the semilunar valve closes. If this occurs, we also could see poor circulation. Poor circulation can result in cold hands and feet! Question 6 --- 2 points Electrical Axis The electrical axis of the heart is the mean or average direction of the action potentials traveling through millions of cells in the heart during depolarization. The QRS complex, which represents ventricular depolarization, is used for the determination of the electrical heart axis. The term electrical heart axis usually refers to the electrical axis in the frontal plane. It is measured by the standard bipolar limb leads I, II and III (I and III are most often used). Watch the video Electrical Axis-1 (links to an external site) to watch a video that shows what an electrical axis is and how to measure it ( 11:48 mins; Electrical Axis - 1 Transcript ; links to an external site). Review the ECG and the Electrical Axis Assignment (links to an external site) which teaches how to measure an electrical axis. If you are taking the lab on campus, you may measure your own electrical axis from your own ECG tracing instead of doing this assignment. Hopefully you downloaded and printed the .pdf file from the assignment above. You probably noticed a coordinate axis page in the assignment. In the text box below, put in the value in degrees of where the electrical axis fell. If you are doing your own electrical axis, show your work to your instructor or TA before entering the value in below. Your answer: 74 degrees

Question 7 --- 1 point If we measure an electrical axis while lying down, it will change when we stand up. In which direction do you think the electrical axis will change in the standing position? Explain. Your answer: When we are standing, gravity is acting on the heart. The heart electrical axis of the heart will be closer to the midline of the body. I think the electrical axis will change to be closer to 90 degrees. Question 8 --- 1 point Abnormal ECG Tracings An ECG looks at how the electrical impulses in your heart “travel.” Many things can change the way action potentials conduct through the myocytes of the heart. You have already examined some things that can change the periods of time between different points on an ECG. Now, we want to look at things that can change the shapes and patterns of an ECG tracing. Learning the characteristics of various ECG abnormalities has proven to be a valuable tool in diagnostic medicine. This part of lab will introduce you to some basic ECG tracings found with well-known alterations (some normal and harmless and others lethal). This Abnormal ECG Patterns (links to an external site) video explains basic abnormal ECG tracings ( 17:38 mins; Abnormal ECG Patterns Transcript ; links to an external site). This abnormal ECG slideshow (links to an external site) will let you work through some practice images of abnormal ECG tracings. Have you gone through the practice slides enough that you easily understand and recognize each of the abnormal patterns there? Check one: ☒ Yes ☐ No Question 9 --- 1 point Taking a Pulse Palpating a pulse involves locating areas on the body where an artery is big enough and close enough to the surface that the systolic pressure waves can be felt. It also helps if the artery can be pressed against a bone so that the pressure in the artery can be amplified. When taking a pulse, it is best to use your index and/or middle finger. Don’t use your thumb, as people can

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often feel their own pulse in their thumb when it is pressed; this will confuse you. If you are not feeling a pulse, it may be that you are pressing too hard. Try to lighten your touch and concentrate. There are key places to palpate. The most common places to check for pulses are as follows: carotid, brachial, radial, femoral, popliteal, posterior tibial, and dorsalis pedis. Read the Pulse Wikipedia page (links to an external site). Find someone to practice on, and see if you can feel a pulse for each of the following:  Carotid (Be very gentle. Don’t press hard!)  Brachial  Radial  Popliteal  Posterior Tibial  Dorsal Pedis Some of these pulses are more difficult than others to palpate. In the text box below, describe your experience. Which pulses were more difficult? Explain why you think some pulses were harder to palpate. Medical professionals will often discover through their experience ways to feel some pulses better. They might change the subject’s position or change the position of their fingers or any number of things. Did you discover anything to help you palpate any of these pulses? Explain. Your answer: When I took the carotid pulse, I found it right away. I believe this is because the carotid artery is very close to the heart, so you can really feel the force of the blood and the pulse is easy to identify. Next, I took the brachial pulse, this pulse was also easy to identify. Something that helped me when identifying this pulse is that I could actually see the vein, so I just put my fingers right over it, and I felt the pulse. The radial pulse was also easy to identify. You have to be pretty gentle with finding this pulse. If you press super hard, you won’t feel it. For me, the popliteal pulse was extremely difficult to identify. I think this is because the artery is deeper and not close to the surface of the skin. I think this pulse would be almost impossible to identify in an obese or very muscular person. I tried identifying this pulse on several different people, and I could only identify it when the person's knee was bent. The posterior tibial pulse was difficult to identify, and it took me quite a few tries. I believe this pulse was harder to identify because it is further away from the heart. The dorsal pedis pulse was also hard to identify. I think this is because I had a hard time finding the dorsalis pedis artery. When I felt the foot I was kind of guessing where the artery would be. I think this pulse will take practice for me to get down, along with all of the others. Question 10 --- 2 points Blood Pressure

Measuring blood pressure requires a sphygmomanometer, or blood pressure cuff, and a stethoscope. At rest, the blood normally travels quietly through the arteries. The blood in the center of the artery travels slightly faster than the blood near the walls of the artery. Think of water flowing in a river. The water near the banks flows the slowest, and as you move toward the middle of the river, the water moves progressively faster. In the blood vessels, this same phenomenon creates multiple layers, or lamina, of blood flowing through the vessels with each subsequent layer moving a little faster as you move closer to the center of the vessel. Due to the physics of this type of flow (laminar flow), there is little mixing of blood between the layers as they move through the vessels. Under certain circumstances mixing can occur, in which case we call the flow turbulent flow. Turbulent flow often creates sounds that can be heard with the stethoscope. When the blood pressure cuff is inflated to a pressure above the systolic pressure of the blood, the blood flow in the vessel stops, and the blood is silent. However, as the pressure in the cuff is gradually lowered, blood will begin to flow through the vessel when the cuff pressure drops below the systolic pressure. The blood is pushed through the partially compressed walls of the artery creating a turbulent flow and creating a detectable sound. Sound is produced in the blood as long as the pressure in the cuff is less than the systolic pressure but greater than the diastolic pressure. As pressure continues to decrease in the cuff, the quality of the sound changes. There are five phases of sound in the vessels under these conditions.  Phase 1. A loud, clear tapping (or snapping) sound is evident, which increases in intensity as the cuff is deflated. This phase begins just as the pressure cuff drops below the systolic pressure of the subject’s blood. The systolic pressure is noted when this sound is first heard.  Phase 2. Is best described as a series of murmurs.  Phase 3 . A loud thumping sound, similar to phase 1, but less clear.  Phase 4 . A muffled thumping sound.  Phase 5 . Silence. This phase begins as the pressure cuff reaches the diastolic pressure of the subject’s blood. The diastolic pressure is noted at the point that the vessel first becomes silent. Blood pressure is measured in millimeters of mercury (mmHg). This is a description of how much pressure is required to raise a column of mercury a certain distance. Optional: If you have a computer that will play flash animations, you may use this blood pressure tutorial (links to an external site; transcript requested). This video will perform how to measure blood pressure (links to an external site) with a sphygmomanometer and stethoscope ( 4:08 mins; How to Measure Blood Pressure Transcript ). Explain in the text box below what causes the first thumping sound (phase 1) and why this represents systolic blood pressure.

Your answer: The first heart sound is represented by the closing of the AV valve during the phase of ventricular contraction. Once all the blood is in the ventricle, the AV valve slams shut, and this causes the first heart sound. This represents the systolic blood pressure because after the AV valve closes, the ventricular volume is at its highest and the ventricles contract (systolic refers to the contraction of the heart.) Question 11 --- 2 points Explain what phase represents the diastolic pressure. What is happening at the heart and vessel level to explain this? Your answer: Diastolic pressure is represented by the relaxation of the ventricles. At the beginning of ventricular relaxation, the semilunar valve closes. At this time, the ventricles are empty. The atrium is filling with blood, but the AV valves are closed so no blood is entering the ventricles. The relaxation/diastolic phase of the heart is much longer than the systole phase. Question 12 --- 1 point Heart Sounds The art of listening to body sounds with the stethoscope is called auscultation. These sounds are often described as “lubb dupp.” The “lubb” portion is also known as the first sound (S1) and is produced by the closure of the AV valves during the first portion of ventricular contraction. The “dupp” or second sound (S2) is heard as the semilunar valves close in response to the relaxation of the ventricles as the pressure within the ventricles becomes less than that in the aorta. There is a sound referred to as the third heart sound (S3), but it is rare. If it occurs, it occurs after the “lubb dupp.” It is generally associated with the sudden and rapid opening of a more rigid than normal ventricle. This sudden opening occurs when blood rushes into the ventricle during the first part of diastole. There is an even more rare fourth heart sound (S4). This sound if it occurs happens just before the “lubb dupp.” It occurs because the atria is contracting more forcibly than normal. This excessive atrial contraction happens usually as an attempt to overcome stiffness and loss of elasticity in the ventricles. Due to the position of the heart, much of the sound produced by the valves is masked by the sternum and ribs. Despite this, there are areas on the chest where individual valve sounds can be heard more clearly. These areas are named according to the valve which can be heard best there. The first is located to the right of the sternum at the second intercostal space and is known as the aortic area. Here you can hear the aortic semilunar valve most clearly. The second is the pulmonic area and is found at the left of the sternum at the second intercostal space. The

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pulmonary semilunar valve can be heard best in the pulmonic area. Since the closing of the semilunar valves is responsible for the 2nd hear sound, the “dupp” will be more pronounced when listening in the aortic or pulmonic areas. The tricuspid valve is heard best when the stethoscope is placed in the 5th intercostal space either just to the right or left of the sternum. Finally, the bicuspid valve can be heard best in the 5th intercostal space in line with the middle of the clavicle (midclavicular line). Since the AV valves produce the first heart sound, when listening in these areas the “lubb” will be more pronounced. Notice that the stethoscope has two listening devices, the bell and the diaphragm. The bell is more sensitive to low frequency sounds, and the diaphragm is more sensitive to high frequency sounds. When doing a routine examination, it is best to listen with both the bell and the diaphragm as some types of abnormalities produce low-pitch sounds and others produce high-pitch sounds. Abnormal heart sounds are called murmurs. These are typically caused by valves that either do not open properly or do not close properly. As the blood moves through these damaged valves it creates sounds that can be heard with the stethoscope in addition to the normal heart sounds. If a valve doesn’t open properly, we say that it is stenotic, or the person has stenosis of a particular valve. The murmur produced by a stenotic valve typically precedes the normal sound for that valve. If a valve doesn’t close properly, we say it is incompetent, and we get regurgitation or backflow of blood through the valve. Murmurs produced by incompetent valves typically follow the normal sound of that valve. If you are attending the campus lab, your instructor will show you how to do these auscultations with a partner. If you have a stethoscope at home, you should try to see what you can hear at the areas mentioned above. Take some time to listen to the following resources:  University of Washington Department of Medicine – Demonstrations: Heart Sounds and Murmurs (links to an external site).  Heart Sounds (links to an external site). Did you practice listening to the heart sounds from both resources? Check one: ☒ Yes ☐ No Question 13 --- 3 points In the text box below, explain what causes each of the four heart sounds (S1, S2, S3, S4). Your answer: The first heart sound is caused by the closing of the AV valves. The second heart sound is caused by the closing of the semilunar valves. The third heart sound is caused by the opening

of the ventricle, there is a rush of blood from atrium into the ventricle. The fourth heart sound is atria contacting.