EKG Worksheet #1

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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: P-Wave means the electrical activity that occurs as the atria contract, or atrial depolarization. This wave is defined by a tiny, vertical wave precedes every QRS complex. A positive wave deflection brought on by depolarization is also known as a P-wave. QRS System means the depolarization of the ventricles and the electrical activity that occurs during their contraction. This wave is defined by a bigger, usually angular wave. The intracellular electrical signal that travels up from the AV Node to the left ventricle is known as the Q wave. All of the electrical signals that depolarize and go through the Bundle Branches to the ventricles make up the R Wave. The electrical impulses compressing back together, and repolarizing is known as the S wave. T-wave means the recuperation of the ventricles, or ventricular repolarization. This wave is defined by following the QRS complex and is somewhat rounded.

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:

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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 represents the time between atrial depolarization and ventricular depolarization. Abnormalities in the timing of the PR segment can indicate pathology. Atrial depolarization (the start of the P wave) and ventricular depolarization (the start of the QRS complex) mark the beginning and conclusion of the PR interval. The PR interval typically lasts between 120 and 200 milliseconds. Numerous events that impact either the AV nodal conduction, the atrial conduction, or both might result in changes in the PR interval. Changes in the conduction channel or the pace of electrical impulse production are often the mechanism causing these changes. Some changes could be a delay in conduction, an alternative pathway for conductions, or a change in the autonomic balance affecting the heart. https://www.ncbi.nlm.nih.gov/books/NBK551635/#:~:text=The%20PR%20interval %20represents%20the,atria%20and%20ventricles%20too%20quickly . Question 3 --- 2 points Blood pressure #2 what 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 heart's ventricles repolarize during the QRS interval. Raising the ion Potassium level will have the effect of changing it. The time elapsed between the first and last Q-wave deflections and the S-wave deflections is represented by the QRS interval. Hyperkalemia is one illness that might alter the QRS interval. The QRS interval may lengthen as a result of this disease. Bundle branch blockages can also happen when they are impacted by an illness or injury that limits their capabilities. 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 time it takes for the ventricle and heart to depolarize and repolarize is known as the QT interval. The Long QT Syndrome is one condition that might create issues with the QT interval. You have this condition from birth. This genetic condition manifests both during and when ventricular repolarization is postponed. The heart then deviates from its regular rhythm, but it soon resumes its regular beat. 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 depolarization of the ventricles and the ST interval are correlated. Myocardial ischemia would be the primary reason for a ST segment intervention. Between the conclusion of the S wave and the start of the T wave, there is an isoelectric interval known as the ST interval. A heart attack, often referred to as a myocardial interference, is one mechanism or circumstance that might alter the ST interval. 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: 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 an electrical axis is in a standing posture, the interventricular septum becomes more parallel to the body's midline mark due to the force of gravity operating on the heart. When the body is in a standing position, the angle at which it is resting will change, causing the heart to move.

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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 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: The posterior tibial pulse was among the pulses that I found most challenging to palpate. It was harder for me than the others since I had less expertise with this type of pulse finding exam. I think that depending on where a pulse is located on the body, some may be more difficult to locate. It could be simpler to locate a pulse in an area of the body where there is more visible veins and arteries and less skin and tissue. It is more difficult to locate a pulse on a more flesh-like region of the body, such the posterior side of the tibia. 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: Systolic blood pressure is indicated by the first thumping sound produced during a blood pressure measurement, or Phase 1 of the Korotkoff noises. This happens when the sphygmomanometer's cuff, which is placed around the upper arm, gradually deflates during a blood pressure check. The compressed artery makes a thumping sound when blood begins to flow again as soon as the pressure in the cuff drops slightly below the systolic blood pressure. The systolic blood pressure is determined by listening to this sound, which represents the force the heart exerts during contraction (systole).

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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: The bottom figure on the blood pressure display is the diastolic pressure. This occurs during phase diastole phase of the cardiac cycle. Meaning when the heart’s ventricles are relaxed and are not contracting. The force that the heart applies to the artery walls in between heartbeats is measured by this device. The cardiac muscles relax during the diastolic pressure. The heart's chambers fill with blood when the heart's muscles relax. As a result, the person's blood pressure lowers. 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 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: S1, S2, S3, and S4 are the four primary cardiac sounds that are audible. This occurs during S1

as a result of the AV valves closing during the initial phase of ventricular contraction. When the semilunar valves open, the second heart sound, or S2, is audible. This is a reaction to the ventricles relaxing when their internal pressure decreases relative to the pressure in the aorta. After the first "lubb dupp" sound, the third and rarest heart sound, or S3, can be heard. It is brought on by the abrupt and quick oping of a ventricle with a jagged edge. When blood rushes through to the ventricles, this occurs. Even more uncommon than the third heart sound is the fourth and final heart sound, or S4. The reason for this is because the atria are contracting harder than usual. The atria use excessive atrial contraction as a coping mechanism for the tension caused by the ventricles' lack of movement.

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EKG Worksheet #1

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