Ekg Measurement and Interpretation at Rest and During Exercise

EKG Measurement and Interpretation at Rest and During Exercise Jonathan Murdock March 5, 2013 March 19, 2013 (KIN 375) Purpose: In the United States, people suffer from heart problems every day. According to the Centers of Disease Control and Prevention (CDC), every year about 935,000 people in the United States suffer from a heart attack and about 600,000 die from heart problems. Electrocardiograms (EKG or ECG) provide important information concerning the electrical activity of the heart as well as the quantity and quality of heart contractions.An EKG, along with blood work to measure troponin levels, can definitively determine whether or not a person has suffered from a myocardial infarction. In order to obtain an EKG, electrodes are strategically placed on the limbs and torso of a subject to measure the electrical current that is generated in the heart and transferred to the skin. The electrical signal is first generated in the sinoatrial node (SA node). It then travels to both th e left and right atria to cause them to contract.Then, the signal goes to the atrioventricular node (AV node) where it is briefly delayed to allow all of the blood from the atria to move into the ventricles. It then moves through the Bundle of His toward the apex of the heart and then through the Purkinje fibers. This causes contraction of the ventricles to pump blood throughout the body and lungs. The purpose of this lab was to compare EKG at rest with and exercising EKG. In doing so, the subject’s heart health could be determined based on the results of being put under the stress of exercise versus when resting.Methods: Subject: The subject participating in this lab was a college aged (18-25 years) male enrolled in KIN 375. The participant was healthy, exercised regularly, and did not report any history of heart problems. Equipment: The equipment used in this lab included alcohol prep wipes, 10 electrodes and wires, a computer to read the EKG with paper to print EKG strips, a chair, a treadmill, and a timer. Procedures: The first step was to remove the subject’s shirt.Next, all of the areas where electrodes were going to be placed were cleaned with an alcohol prep wipe. Once these areas were dry, electrodes were placed in their proper places; one electrode per limb and six on the torso. The electrodes for the left (LA) and right (RA) upper limbs were placed just under the clavicles near the shoulders. The electrodes for the left (LL) and right (RL) lower limbs were placed at the waist line just above each limb. For the torso, electrode 1(V1) was placed in the fourth intercostal space to the right of the subject’s sternum.Electrode 2 (V2) was also placed in the fourth intercostal space but to the left of the subject’s sternum. Next, electrode 4 (V4) was placed in the fifth intercostal space on the midclavicular line. Then, electrode 3 (V3) was placed halfway between V2 and V4. Next, the sixth electrode (V6) was placed in the fifth intercostal space on the midaxillary line. Lastly, the fifth electrode (V5) was placed halfway between V4 and V6 in the fifth intercostal space. The subject sat on the chair without moving for three minutes to generate a resting EKG.Then, the subject walked 2 mph on the treadmill with a 7. 0% incline for five minutes. This generated an exercising EKG. Lastly, the subject sat on the chair without moving for three minutes to generate a recovery EKG. Results: The subject successfully completed all three EKG recordings. The resting and recovery EKG readings were very easy to read; whereas, the exercising EKG had a lot of artifact that made it difficult to read. Artifact is something that is not â€Å"heart made† and usually comes from movement.The exercising EKG also had the most QRS complexes due to the fact that the subject’s heart rate was the highest while exercising. Discussion: As previously stated, an EKG measures the electrical currents of the heart. There are diff erent waves shown on an EKG. Each wave is represented by a letter. The first small wave is known as the P wave. The P wave represents atrial depolarization and contraction. The next wave is slightly negative and it is known as the Q wave. The Q wave initiates depolarization of the ventricles.The next wave, which is the large positive spike in the wave, is known as the R wave. The R wave represents ventricular depolarization and contraction. The next wave is slightly negative and it is known as the S wave. The S wave represents the negative wave of ventricular depolarization. The last wave is slightly larger than the P wave and it is known as the T wave. It represents ventricular repolarization and relaxation. Since there are three waves that represent ventricular depolarization, they are combined into what is known as the QRS complex.The section of the EKG from the beginning of the P wave to the beginning of the QRS complex represents the ventricular fill time and is known as the PR interval. Ventricular systole, or contraction, is shown by the start of the Q wave to the start of the T wave and is known as the QT interval. Lastly, from the end of the S wave to the start of the T wave, ventricular repolarization is normally isoelectric (on the baseline) and is represented by the ST segment. Any slight changes from normal sinus rhythm in any of these waves could indicate a heart problem.Electrodes were used to measure the electrical current in the heart. The paths from each electrode to another created a lead. Lead I was the path between RA and LA. Lead II was the path between RA and LL. Lead III was the path between LA and LL. The ground electrode was RL. An EKG wave read positive when the current moved toward a positive electrode and it read negative when the current moved toward the negative electrode. At rest, the EKG was much â€Å"cleaner† (less artifact) and the P waves, QRS complexes, and T waves were much easier to identify.During exercise, howev er, these waveforms were much more difficult to identify because of the large amount of artifact. Compared to at rest, the waveforms were much steeper and quicker which indicated the heart rate was speeding up, contraction and filling times decreased, and the contractions were much more forceful to pump the blood to the necessary tissue. There were a couple factors that could have hindered a completely accurate EKG reading; such as, cheap electrodes, movement of wires, and the placement of electrodes.All of these factors could have affected the EKG reading to cause extra artifact or inaccurate readings of the electrical current. Conclusion: Every year, hundreds of thousands of people die from heart problems. Many of these heart problems could be detected if the individuals had received an EKG. An EKG measures the electrical currents of the heart and shows when there are defects or blocks by the change in waveform. If more people were able to have an EKG when the problems arose, then maybe more lives would have been saved.