The electrocardiogram is a test performed to make sure all electrical activity of the heart is normal and working properly. “By positioning leads (electrical sensing devices) on the body in standardized locations, information about many heart conditions can be learned by looking for characteristic patterns on the EKG.” KULICK, MD, FACC, FSCAI (2016) The activity is shown as spikes and dips called waves on the tracing paper, that comes out of the ECG machine. These waves create different waveforms to be analyzed for diagnoses. A waveform is movement recorded that is away from the baseline, either positive or negative.
The P- QRS- T sequence is the measurement of one heartbeat. “One cardiac cycle is equivalent to one complete heartbeat.” Jones. (06/2014) p. 8. When broken down there are three separate sequences the P-wave, QRS, and the T-wave. These three sequences represent depolarization, depolarization and then repolarization which produces contractions in the heart. The QRS complex is represented by the second depolarization activity picked up by leads. This wave form is created by the depolarization of the ventricles. The QRS complex can be represented by any one, two, or three combinations of the three waves and still recognized as the QRS waveform.
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The shape of the QRS complex consists of the Q wave, which is the negative deflection before the R wave, then the R wave, that is the first positive deflection after the Q wave, and the S wave, which is the first negative deflection after the R wave. “The normal duration of a QRS complex is about 0.10 second when the speed and direction of depolarization are normal and the voltage (amplitude) generated during ventricular depolarization are normal.” Jones (06/2014) p. 137. Amplitude of the QRS complex varies but the normal range is 5mm to 15mm
There are several different heart problems that show up as an abnormal EKG reading. For example, a heart block can occur when there is a delay in the signals coming from the SA node, AV node, or the Purkinje fibers. However, clinically the term heart block is used to refer to an AV block. This delays or completely stops communication between the atria and the ventricles. AV block is shown on the EKG as a delayed or prolonged PR interval. The P wave represents the activity in the atria, and the QRS complex represents ventricular activity. This is why the PR interval shows the signal delay from the AV node. There are three degrees of severity, and if the delay is greater than .2 seconds it is classified as first degree. Second degree is classified by several regularly spaced P waves before each QRS complex. Third degree can be shown by P waves that have no spacing relationship to the QRS complex. Another type of blockage is bundle branch block. This is caused by a blockage in the bundle of His, creating a delay in the electrical signals traveling down the bundle branches to reach the ventricles. This results in a slowed heart beat, or brachycardia. On an EKG reading this is shown as a prolonged QRS complex. A normal QRS is about .8-.12 seconds, and anything longer is considered bundle branch block. Another type of abnormal EKG reading is atrial fibrillation, when the atria contracts very quickly. On the EKG this is shown by no clear P waves, only many small fibrillating waves, and no PR interval to measure. This results in a rapid and irregular heartbeat. On the other hand, ventricular fibrillation is much more serious and can cause sudden death if not treated by electrical defibrillation.
622 Y. When the AV node receives the signal, it fires and causes the ventricles to depolarize, this is known as the QRS Complex. The atria also repolarizes during this phase. Specifically in the QRS Complex, during the Q wave, the interventricular septum depolarizes, during the R wave, the main mass of the ventricles depolarizes, and during the S wave, the base of the heart, apex, depolarizes. After the QRS Complex, the S-T segment can be identified as a plateau in myocardial action potentials and is when the ventricles actually contract and pump out blood to the pulmonary and systemic circuits. The final phase of the heartbeat is the T wave and this is when the ventricles repolarize before the relax, ventricular diastole, EKG Video Notes and pg. 671 D. These phases represent the cardiac cycle, which is the time and events that occur from the beginning of one heartbeat to the beginning of the next heartbeat. In this lab, the first EKG that I took was my regular heartbeat during rest. In this recording, I was able to see the P wave, followed by the QRS Complex and the T wave as well. Everything looks pretty normal, but the T wave does go a little lower than normal and I believe this is due to the fact that I was diagnosed with sinus bradycardia
1.2 & 1.3 Explain The Cardiac Cycle And Describe How The Heart Rate Is Modified According To The Needs Of The Body
Which of the following is NOT part of ECG Changes that is associated with MI?
When evaluating systolic and diastolic function it is extremely important to obtain images of wall motion, wall thickness, chamber size and ventricular end diastolic pressure.
In a normal strip, one can clearly identify a P wave before every QRS complex, which is then followed by a T wave; in Atrial Fibrillation, the Sinoatrial node fires irregularly causing there to be no clear P wave and an irregular QRS complex (Ignatavicius & Workman, 2013). Basically, it means that the atria, the upper chambers of the heart, are contracting too quickly and no clear P wave is identified because of this ‘fibrillation’ (Ignatavicius & Workman, 2013). Clinical Manifestations and Pathophysiology A normal heart rhythm begins at the sinoatrial node and follows the heart's conduction pathway without any problems. Typically the sinoatrial node fires between 60-100 times per minute (Ignatavicius & Workman, 2013).
The study of cardio physiology was broken up into five distinct parts all centering on the cardiovascular system. The first lab was utilization of the electrocardiogram (ECG). This studied the electrical activities of the heart by placing electrodes on different parts of the skin. This results in a graph on calibrated paper of these activities. These graphs are useful in the diagnosis of heart disease and heart abnormalities. Alongside natural heart abnormalities are those induced by chemical substances. The electrocardiogram is useful in showing how these chemicals adjust the electrical impulses that it induces.
Abnormalities that are being examined includes some arrhythmias, such as premature ventricular contraction or atrial fibrillation.
Other than atrial fibrillation and atrial flutter, this is the most common supraventricular tachycardia seen in practice.11 A large minority of adults (up to 40% in some cohorts) are born with 2 pathways that can conduct electricity in the AV node, rather than 1. Under the right conditions, AV node reentrant tachycardia (AVNRT) can be initiated by a premature atrial or ventricular beat. If the 2 pathways are able to sustain a stable circuit, the atrium and the ventricle are depolarized almost simultaneously. As a result, on the ECG, the P wave is not seen, is buried in the QRS complex, or is seen at the terminal portion of the QRS, typically as a pseudo-s (negative) wave in the inferior leads or a pseudo-r0 in lead V1. Because this tachyarrhythmia depends on the AV node, both vagal maneuvers and adenosine are potential acute treatment options. In the outpatient setting, if the patient is in a sustained supraventricular tachycardia, attempting vagal maneuvers
The ventricular ectopic pacemaker produced the rhythms as 30-40 beats/minutes much slower than the generally produced by SA node which is 60-100
AIM: - the aim of this experiment is to find out what the effects of exercise are on the heart rate. And to record these results in various formats. VARIABLES: - * Type of exercise * Duration of exercise * Intensity of exercise * Stage of respiration
blood from the ventricle chambers during systole. Reduction in the contraction is caused by the increase
Due to the fact that we thrive in a prevalent world of technological advances significantly more convenient machines have been granted. Furthermore, the diagnostic tests that can be done to evaluate heart function are:
The ECG has had a huge impact on society in many ways. Among the most beneficial is that the data collected can be extrapolated to predict heart disease in an individual and thus lead the individual to alter their lifestyle, whether by taking medication or changing diet and exercise routine (3). This is increasingly relevant with the rising number of healthy, young athletes dying from sudden cardiac arrest after showing no previous symptoms (5). With the data collected by the electrocardiogram, this can be predicted and thus save lives. One harmful effect of the ECG is that the data is not always reliable; sometimes the data will find false-positive evidence of heart disease or a heart attack when there is none, and in other cases, the device isn’t consistently able to predict heart disease in people without a high risk of having heart problems (1). Overall, however the ECG is a device that ultimately will benefit people and reduce the number of lives taken by heart
Decreased cardiac output r/t altered heart rate as evidenced by ECG results, irregular HR, and HR of 165 beats per minute.