shortcut to ecg
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DESCRIPTIONSalient features of the book are - - The book provides a shortcut to understand and remember certain specific formulae and points you require to interpret the 12-lead ECG. - Treatment protocols (in green boxes) for most of the important conditions are also included. - View sample ECGs as you read along the topics. - The content is explained in a very simple language to provide good conceptions, written from a student’s point of view. - People can gain their belief in the book after going through sample ECGs which would be available at www.themedicalpost.net/ecg - The book competes with the other books available in the market in simplicity, summaries, treatment protocols, live diagrams and regularly updated sample ECGs on the website.
- 1.The Medical Post Shortcut to ElectrocardiographyShortcut toElectrocardiography The Medical Post Publicationswww.themedicalpost.net The Medical Post - Shortcut to Electrocardiography
2. Shortcut to ElectrocardiographyUtmost care has been taken to confirm the accuracy of theinformation compiled on this book. However, the compilers /authors and the publisher are not responsible for any errors or forany consequences from application of the information in this book.It is the responsibility of the physician to ascertain the FDA status ofeach drug or device planned for use in their clinical practice.As the name suggests this book provides you only a shortcut tointerpret an ECG. This book in any way does not replace the need ofstandard textbooks.After going through this book, you may access some sample 12-leadECGs at www.themedicalpost.com/ecg2 3. Shortcut to ElectrocardiographyThis book is dedicated to our parents. 3 4. Shortcut to ElectrocardiographyPrefaceIn the preface of our first book we would like to share that whywe had chosen this topic Electrocardiogram.As doctors we all know the ultimate need for understanding anECG. Its importance is known to everyone as it is the simplestsource of diagnosing a large number of diseases and conditionnot only related to the heart but other systems too.As titled the book provides with a shortcut that you can rely onfor understanding and describing an electrocardiogram.This book cannot change the need of standard textbooks but itwill provide you with all the specific points to learn andremember, helping you to interpret the 12 lead ECG withinseconds.One important feature of this book is the Treatment box. Withevery disease or a condition, specific treatment regimens andprotocols are described in brief. In this way this book will notonly help you to diagnose conditions easily but will also help youto remember important drugs and doses which may even be lifesaving in many cases.I hope our first project will make a good impression on everyoneand will benefit medical students specially the interns to themaximum.We would like to thank Manbir Singh for guiding us and tomake this project a success.We would also like to thank Ram Kaji Baniya and ShankarBaral for their help. GURKEERAT SINGHJASKEERAT SINGH RAVI KUMAR SHAH4 5. Shortcut to Electrocardiography ContentsChapter 1Important basics you need to know.6-8Chapter 2ECG leads.9-11Chapter 3Naming the lines. 12-15Chapter 4Relationship of different waves, segments 16-17 and intervals in different leads.Chapter 5Axis determination. 18-19Chapter 6Hypertrophy and Enlargement.20-23Chapter 7Arrhythmias (including atrio ventricular 24-40 blocks).Chapter 8Ischemic heart diseases.41-44Chapter 9Pre excitation syndromes. 45-46Chapter 10 Bundle branch blocks. 47-48Chapter 11 ECG changes seen in electrolyte 49-50 imbalances.Chapter 12 ECG changes associated with other 51 systems.Chapter 13 Stepwise approach for reading a 12-lead 52 ECG. 5 6. Shortcut to ElectrocardiographyChapter 1. Important basics you need to know.Letus first let be familiar with common terminologies.Electrocardiography is the interpretation of the electrical activity of theheart over a period of time, as detected by electrodes attached to theouter surface of the skin and recorded by a device external to the body.The recordingproduced bythis procedure is termed asElectrocardiogram.There are 3 types of cells in the heart.1. Pacemaker cells These cells are responsible for the cardiac rhythm. They can further be grouped in atrial, junctional and the cells in the ventricles. Remember those pacemaker cells that are dominant takes over the rhythm. Normally the dominant cells are located high up in the right atrium. These groups of cells are called as the Sino Atrial (SA) node. In normal conditions it fires at a rate of 60-100 times a minute.2. Electrical conducting cells They are like wires of an electrical circuit. They carry current rapidly and efficiently to distant regions of the heart.3. Myocardial Cells These are responsible for heavy labour of contracting and relaxing of the heart. Composed of abundant contractile proteins actin and myosin. When the wave of depolarization reaches the myocardial cells Calcium is relased from the cells causing it to contract. This is the famous excitation contraction coupling.6 7. Shortcut to ElectrocardiographyThe conduction pathway in brief SA NODE ATRIAL CONDUCTION SYSTEM AVNODE BUNDLE OF HIS DIVISION INTO Right bundle branch Left bundle branch Septal fascicle, Left anterior fascicleand Left posterior fascicle. PURKINJE FIBERSFig 1.1 Electrical conduction of the heart. [Source Wikipedia. Author Madhero88].Note that all the lines/waves we see on the ECG are produced as aresult of the function of the myocardial cells. Rests of the cells do notgenerate sufficient voltage to be recorded by the surface electrodes.HistoryWillem Einthoven used his invention String galvanometer andassigned the letter P, Q, R, S and T to the various deflections anddescribed the electrocardiographic features of a number ofcardiovascular disorders. In 1924, he was awarded the Nobel prize inmedicine for his discovery.7 8. Shortcut to ElectrocardiographyECG PaperLet us understand the ECG paper now Light lines describe small squares each of 1 x 1 mm size. Dark lines describe large squares each of 5 x 5 mm size. X axis denotes time 1 small square = 0.04 seconds. Y axis denotes the amplitude of the wave produced 1 smallsquare = 0.1 mV. Fig 1.2 Dimensions of the ECG paper.8 9. Shortcut to Electrocardiography Chapter 2. ECG leads.There are two types of leads Limb leadsand precordial (chest) leads.The reason we use these two leads is thatthe heart is a 3 dimensional structure, thus asingle lead will not be able to describe itselectrical activity properly. Hence thestandard ECG consists of 12 leads. Eachleads views the heart at a unique angleenhancing its sensitivity to a particularregion of the heart.Limb LeadsThese leads view the heart in the vertical plane i.e. records theelectrical forces (depolarization and repolarization) moving up,down, left and right.To produce the 6 limb leads with 4 actual leads. Each of theelectrodes is variably designed as positive and negative. This isdone automatically by the machine.Various limb leads again further grouped into Standard limbleads and Augmented limb leads.The standard limb leads are,Lead 1 (0 degree): Left arm is made +ve and Right arm -ve.Lead 2 (60 degrees): Legs +ve and Right arm ve.Lead 3 (120 degrees): Legs +ve and Left arm -ve.9 10. Shortcut to ElectrocardiographyThe augmented limb leads are,AVR (-50 degrees): Right arm is +ve and other limbs are ve.AVL (-30 degrees): Left arm +ve and other limbs are ve.AVF (90 degrees): Legs are +ve and other limbs are ve.Note these augmented are so named as they amplify the tracingsto get an adequate recording.Precordial leadsThe precordial leads view the electrical forces moving anteriorlyand posteriorly.These are,V1: Placed in the 4th intercostal space right to the sternum.V2: Placed in the 4th intercostal space left to the sternum.V3: Placed between leads V2 and V4.V4: Placed in the 5th intercostal space in the mid clavicular line.V5: Placed between the leads V4 and V6.V6: Placed in the 5th intercostal space in the mid axillary line.Leads specifying different region of the heartInferior leads: Leads II, III and AVF. They view the inferiorsurface of the heart more effectively.Left lateral leads: Leads I, AVL, V5 and V6. They best view theleft lateral wall of the wall.Anterior leads: V1, V2, V3 and V4.Note: The right ventricle lies anteriorly and medially and the leftventricle lies posteriorly and laterally. Thus;V1 and V2 lies directly over the right ventricle.10 11. Shortcut to ElectrocardiographyV3 and V4 lies over the interventricular septum.V5 and V6 lies over the left ventricle.Remembering the region specific leads is of great importance in Ischemic heartdiseases.Fig 2.1 Figure showing angle of orientation of all the limb and chest leads.11 12. Shortcut to ElectrocardiographyChapter 3. Naming the lines.Before we can start naming the lines it is important tounderstand them first.A segment is a line connecting 2 waves.An interval is composed of at least one wave plus a connectingstraight line.Well be discussing these waves/segments as the cardiac cyclecontinues.P waveAs the SA node fires (an event which is not seen on the ECG)the wave of depolarization spreads outward into the atrialmyocardium which results in depolarization of the atrialmyocardial cells producing atrial contraction. This forms the pwave on the ECG.Hence p wave is the recording of the spread of wave ofdepolarization. Now as the SA node is located in the right atriumthus the right atrium will be depolarized first and so the first halfof the p wave is formed by the right atrial depolarization and theremaining half by the left atrium. Fig 3.1 Figure showing the two components of the p wave.Now the wave of depolarization is prevented fromcommunicating the ventricles by the valves. Thus the electricalconduction funnels its way along the interventricular septum.12 13. Shortcut to ElectrocardiographyHere a structure know as the AV node slows down theconduction to a crawl but this pause only lasts for a few fractionsof seconds.Why is this pause necessary? Its really important as it allows theatria to contract completely and allows them to empty theirwhole content before the ventricles starts to contract.The wave of depolarization now enters the ventricularconduction systems. The waves first enters the bundle of hiswhich then divides into right and left supplying the respectiveventricles. The left bundle of his further divides into 3 fascicles Left anterior f., Left posterior f. and the septal fascicle.The wave then passes to the ventricles causing depolarization.This is marked by the QRS complex on the ECG.Note that the amplitude of the QRS complex is much more thanthe p wav