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ECG Recording Clinical Skills ECG Recording Dawn Lau, Spring 2011 ECG Recording Learning Objectives Learning Objectives To learn how to record a full, detailed tracing of the electrical activity of the heart, using an ECG (electrocardiograph) machine recorder; That is, ‘How to perform a 12-lead ECG’ How to set up a continuous recording of the ECG ie cardiac monitoring • • ECG rhythm strip ECG tracing ECG Recording What is an ECG? What is an ECG? The electrocardiogram (ECG) is a record of the electrical conduction activity of the heart, and is represented by waveforms which are formed by the net result of electrical vectors flowing within the conduction system of the heart. The waveform looks different in appearance depending on from which angle and plane one ‘looks’ at the heart. His-Purkinje Conduction system ECG Recording What is an ECG? What is an ECG? The 12-lead ECG thus gives an ‘electrical map’ of the heart’s activity and crucially enables one to identify cardiac conduction abnormalities and ischaemic heart disease. ECG rhythm strip using Lead II ECG Recording Standard ECG Calibration Standard ECG Calibration The ECG is recorded on to standard paper travelling at a rate of 25 mm/s. The paper is divided horizontally into: • 1 small square = 1 mm wide = 0.04 s • Each large square contains five small squares in width • 1 large square = 5 mm wide = 0.2 s The electrical activity detected by the ECG machine is measured in millivolts. Machines are calibrated so that a signal with an amplitude of 1 mV moves the recording stylus vertically 1 cm: • 1 small vertical square = 0.1 mV = 1 mm Hence, always look at bottom of any ECG to ensure the standard 25mm/s; 10mm/mV or equivalent (or else you may find yourself misinterpreting the rate/sizes of waveforms!) ECG Recording How to do a 12-lead ECG How to do a 12-lead ECG Equipment Preparation Procedure Equipment: Take time to familiarise yourself with the machines and equipment Watch how it’s done on the ward or cardiology investigations unit ECG Recording Preparation Preparation Patient • • • Patient position – comfortable on a trolley/bed, about 45° incline Expose chest and distal limbs Consider shaving chest at locations of ECG electrode placement Machine • The obvious, but ensure machine is switched on and ECG grid paper is fitted in. • Check that speed and calibration settings are set correctly (this is usually ‘default’ on the ECG machine, but be aware) ECG Recording Cardiac Monitoring Cardiac Monitoring Gives a ‘real-time’ ability to monitor cardiac electrical activity There are quite a variety of equipment to do just that, although the basic aspects and features of each equipment are similar. It’s helpful therefore to familiarise yourself with a machine you come across on the ward, and ask the Nurse to show how to use it on a patient. This advice particularly holds great importance with the defibrillator machine – know its dials and buttons – in the event that you may eventually have to operate it during a cardiac arrest. A few of these equipments are shown here: – Bedside monitoring and ECG electrode stickers – Cardiac monitoring in the coronary care unit (CCU) – Cardiac defibrillator machine The ECG machine, besides a 12-lead ECG, can also be made to record a rhythm strip with a press of the appropriate button. ECG Recording ECG rhythm strip ECG rhythm strip The ECG strip gives additional information to the 12-lead ECG. It gives a view from one lead and its role, as the name suggests, is to produce a temporally longer recording of the ECG so as to facilitate in the identification and monitoring of the abnormal rhythm. This is particularly useful in: • Profound bradycardia • Profound tachycardia • Real-time recording of a therapeutic/diagnostic intervention e.g. administration of i.v. adenosine, or electrical cardioversion. ECG Recording Bedside Cardiac Monitoring Bedside Cardiac Monitoring Usually patients requiring cardiac monitoring are attached to a portable bedside 3-lead monitor. The electrodes (with colours of electrodes shown) are placed in 3 spots: • Right shoulder, Left shoulder and Left rib cage R shoulder L shoulder L ribcage ECG Recording Cardiac Defibrillator Cardiac Defibrillator You will have the opportunity (if not already) to learn the Advanced Life Support (ALS) algorithms, which are beyond the realm of this module; however this picture shows a commonly used defibrillator on a medical ward. Get familiar with it. ECG Recording Functions of the Cardiac Defibrillator Machine Functions of the Cardiac Defibrillator Machine This machine has combined functions: • ECG display screen • Defibrillator function • Cardioversion function • External pacing function for bradyarrythmias The ECG display screen allows for ECG monitoring, using either leads or pads applied to the anterior chest. The difference between ‘defibrillation’ and ‘cardioversion’ is dependant on the type of the dysrhythmia and the level of compromise to the patient. Defibrillation: electric current treatment for immediately life-threatening arrhythmias in which the patient does not have a pulse e.g. VF and pulseless VT. Cardioversion: process that aims to convert a tachy-arrhythmia back into sinus rhythm. Electrical cardioversion is considered in these dysrhythmias with pulse which are haemodynamically unstable (pharmacological means will take too long to act in these situations); or in elective situations where pharmacological cardioversion has failed or unlikely to be successful. ECG Recording Functions of the Cardiac Defibrillator Functions of the Cardiac Defibrillator So, in ‘Sync’ mode, you will commonly experience a transient delay from the moment you press the ‘Shock’ button to the moment the machine delivers the shock to the patient on the next R wave. In contrast, the defibrillator mode will deliver the shock the instant you press the ‘Shock’ button. The pulse-less life-threatening arrhythmias for which the defibrillator is indicated has no need (and indeed is impossible in VF) for a synchronised shock. ECG Recording Practical Tips Practical Tips Accurate and consistent positioning of electrodes – so that serial ECGs can be compared Good electrode-to-skin electrical contact: • Chest wall should be clean and dry, so wipe off sweat; oil or grease with alcohol wipes. • May have to shave off chest hair in appropriate places as hair is a poor conductor of electrical signal, and may also interfere with the sticking ability of electrodes. A relaxed and comfortable patient – to minimise ‘noise’ and interference from skeletal muscles/movements and optimise quality. Wait for the real-time tracing on the ECG machine screen to look of good and consistent quality before pressing the ‘Print’ button. Remember the speed and calibration settings are set correctly (this is usually ‘default’ on the ECG machine, but be aware) ECG Recording Summary Summary It is a basic clinical skill to record a 12-lead ECG (electrocardiograph) using an ECG machine recorder as well as to record a rhythm strip. Familiarise yourself with the various machines which record cardiac monitoring: the bedside monitor, the cardiac defibrillator machine, the ECG machine recorder. The 12-lead ECG gives an ‘electrical map’ of the heart’s activity and crucially enables one to identify cardiac conduction abnormalities, certain structural abnormalities and ischaemic heart disease. The ECG rhythm strip adds further information and is useful particularly in very slow or fast heart rates, and records interventions to treat arrythmias. ECG Recording Resources & References Resources & References A mere selected few give clear background and excellent know-how on interpreting ECGs: Hampton JR. (2008). The ECG made easy. (7th Ed) Churchill Livingstone. Also by John R Hampton: The ECG in Practice (5th Ed); 150 ECG problems (3rd Ed). Churchill Livingstone. Morris F, Brady WJ, Camm J (Eds) (2008). ABC of clinical electrocardiography. (2nd Ed) Blackwell Publishing/BMJ Books. Longmore M et al (2010). Oxford Handbook of Clinical Medicine. (8th Ed) Oxford University Press. James S Fleming: Interpreting the Electrocardiogram (1979). Resuscitation Council (UK) (2010). Resuscitation Guidelines. Downloaded at www.resus.org.uk ECG Recording Acknowledgements Acknowledgements Dr Zaheer Yousef, Consultant Cardiologist, UHW Joshua Dimbylow, Medical E-learning Developer Cardiac Investigations Department, University Hospital of Wales for the use of the ECG machine Media Resources Team – Carl Rogers Medical Photography; Amy Lake, Bolette Jones & team B1 Cardiology Staff including Caroline and Sonia http://www.patient.co.uk/doctor/Defibrillation-and-Cardioversion.htm cardiology.ucsf.edu/ep/Imagesheart/normalecg.jpg www.ctsnet.org/graphics/experts/Adult/cosav1.jpg http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/resources/ ECG Recording Student Feedback Student Feedback When you have completed the module, please take time to complete the student survey. 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