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اخ بار The 12 Lead ECG Tutorial ۱۳۹۲/۱۰/۲۳ The 12 Lead ECG Tutorial Learn about lead placement and how they work to diagnose cardiac conditions and other injuries. Learn about lead placement and how they work to diagnose cardiac conditions and other injuries. By Sue Durkin, MSN, CCRN, CCNS The 12 lead electrocardiogram or ECG is a valuable diagnostic tool for assisting in the diagnosis of cardiac disorders or acute injury events. Knowledge of lead configuration, proper skin preparation and placement are components to obtaining an accurate picture of cardiac activity. An understanding of cardiac anatomy, the electrophysiology of the conduction system and basic rhythm interpretation knowledge will be helpful in understanding the 12 lead ECG tracing. This tutorial will focus on proper lead placement and various waveform representations. History While the first electrical current associated with a heart beat was identified in 1842 by an Italian physicist, it was a British scientist, Augustus Waller, who published the first human ECG in 1887. And, it was not until 1893 that Dutch scientist, Willem Einthoven, introduced the term "electrocardiogram" and subsequently refined the concept of cardiac electrical conduction, naming the deflections P, Q, R, S and T waves. Those same basic waves are used today to identify and interpret the ECG rhythm strip.1 Einthoven's concept was a triangle, an imaginary area on the body, formed by the intersection of the standard bipolar limb leads with the heart at the center. The bipolar leads have a negative and positive pole that captures the direction of the electrical activity of the heart in the various lead configurations. Looking at the heart from the various electrical vectors that are produced helps determine which way the impulse is traveling. Standard Limb Leads The hexaxial system of looking at the heart basically cuts the center of the heart in half into two planes, a front and back, combining the view from leads I, II and III and creating three additional augmented vector pictures in AVR, AVL and AVF. These three additional vectors complete the standard six limb leads with the notion that the positive electrode lies at the end of the lead name. If a camera is placed at the end of the positive electrode, looking toward the negative pole, the electrical impulse of the heart's activity passing under would create the ECG tracing. As the heart normally depolarizes from right to left, a positive impulse moving away from the camera would create a negative deflection of the QRS wave on the ECG tracing. While a positive impulse moving toward the camera would be recorded as a positive or upward wave on the tracing. 2 The Precordial System The six unipolar precordial leads are those that lie directly on the chest wall and in a theoretical plane perpendicular to the limb leads. Thus creating a transverse plane through the center of the heart cutting it into a top and bottom half. Combining all three planes together (the front, back, top and bottom) will now give a 3D picture of the heart, and the electrical activity recorded will be a reflection of the subsequent mechanical or muscular contraction with each cardiac beat or cycle. The six precordial leads are those named V1, V2, V3, V4, V5 and V6. All leads give a view of the heart, which when combined together, transmit a wealth of diagnostic information used to identify physiologic or pathologic processes occurring with cardiac function. For identification of arrhythmia to hypertrophies and infarcts, the 12 lead ECG is an indispensable tool for use in daily healthcare practice. Lead Placement Correct electrode and lead placement is important to receive an accurate rhythm strip tracing. Laying the patient supine or in a comfortable reclined position will allow easier access to the upper body. Most importantly, proper skin care is the first step to assure reliable results. Skin should be clean, dry and free of hair, oils or substances that may interfere with placement or conduction to the electrode. Hair should be clipped and lead placement should avoid implanted devices such as pacemakers or catheters that could impede signal transmission. Avoiding boney prominences, open wounds and very muscular or hairy areas will provide a more accurate picture. While exact placement for limb leads can vary, correct precordial lead position is essential. What the Leads Tell Us The sum of the total 12 lead system gives a wealth of information to the practitioner during controlled or emergent situations, essentially directing treatment and interventions for care. An important concept to remember is that the electrical activity of the heart precedes the mechanical function of the cardiac cycle. And, each wave is associated with a particular function of the cardiac cycle. Changes in the specific waves can indicate abnormalities in heart chamber size, electrolyte values, acute myocardial infarction or STEMI patterns and electrical conduction defects as a result of ischemia, clot or hypertrophic changes related to congestive failure. Reviewing trends in wave form pattern changes can be important in determining treatment for acute coronary syndromes where ischemia often precedes injury. Follow the guidelines from the American Heart Association for prevention of cardiac syndromes and when determining treatment for acute injury events. Use the12 lead ECG as a tool in the armamentarium of options to prevent and treat cardiac emergencies. Definition Page 12 lead electrocardiogram: This is a recording that provides a trans thoracic view of the electrical activity of the heart on a strip of paper in a set time frame used to assist with diagnosis of cardiac events. (Permission to use the following ECG rhythm strips granted by NewCardio Inc.) Lead configuration: The placement of electrodes on the body in a set order to relay a picture of the electrical activity of the heart. Through analysis of the 12 specific leads, physiologic and pathologic patterns of activity can be determined. Cardiac anatomy: The specialized structures within the heart muscle that encompass the four chambers, two atria, two ventricles, four heart valves, sinoatrial node, AV node, bundle branch and purkinje system of conduction. This also includes the great vessels of the heart, the aorta, superior and inferior vena cava, and pulmonary veins and coronary circulation system. Electrophysiology: This relates to the electrical activity of the heart and analysis of function. Conduction: The intrinsic electrical stimulation of specialized cells of the cardiac system that allows impulses to propagate throughout the various nodes, fibers and chambers within the heart. P, Q, R, S, T Waves: The P wave denotes the specific electrical action of the synchronous depolarization of both atria. The QRS complex represents a simultaneous depolarization of the right and left ventricles. While the ST segment and T wave symbolize the re polarization of the ventricles.3http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson1/index.html#orientation Permission to use image granted byHealth Education And Rescue Training, at [email protected]. Vectors: This term relates to a force or velocity and is often shown by an arrow indicating direction. Hexaxial: A system referring to the imaginary planes of the heart that divide it into front, back and top and bottom through the intersection of the limb leads. Precordial leads The precordial leads lie on a horizontal plane on the chest with a unipolar view of the heart where the anatomically placed position is the positive pole. As the impulse moves toward or away from the positive pole, the waveform will be noted as positive or negative. In the case of V1, the QRS wave form is negative. Limb leads: The standard limb leads are placed so the tracing on the recording device, the ECG machine, reflects the activity of the heart with a view of the impulse moving either toward or away from the positive electrode in various locations, giving the resulting picture of an upward or downward QRS waveform. In other words, the ECG is a reflection of the many vectors or courses of an electrical impulse as it passes beneath the electrode. The electrodes placed on the upper and lower extremities give origin to leads I, II, III, AVR, AVL and AVF. Angle of Louis: The sternal or the anterior angle that is formed by the junction of the manubrium and sternum. Acute myocardial infarct: The rhythms on the ECG strip that denote acute myocardial muscle injury. STEMI patterns: ST elevation myocardial infarction waves denoted on the ECG rhythm strip. Ischemia: Inadequate blood supply to the heart muscle. Hypertrophy: The enlargement or dilation of a chamber of the heart in an effort to overcome increasing pressure. Acute coronary syndromes: A generalized term for conditions such as chest pain where there is a disruption or blockage of the blood supply to the heart muscle. 4 TAKVIN TEB R&D 1/13/2014 دی دگ اه خود را ب یان ک ن ید نام شما ا يميل شما ( نمايش داده نميشود) سايت شما