Presented By:Aamir SharifBEMS Final ProfessionalDept. Of EMS The University Of Poonch Rawalakot AJ&KELECTROCARDIOGRAPHY
Objectives• The Basics• Interpretation• Clinical Pearls• Practice Recognition
Introduction• The electrocardiogram (ECG) is one ofthe simplest and oldest cardiacinvestigations available, yet it canprovide a wealth of useful informationand remains an essential part of theassessment of cardiac patients.
The ECG“An ECG is simply a representation of the electricalactivity of the heart muscle as it changes withtime, usually printed on paper for easier analysis”Like other muscles, cardiac muscle contracts inresponse to electrical depolarization of the musclecells. It is the sum of this electrical activity, whenamplified and recorded for just a few seconds that weknow as an ECG.
Cont.....• The ECG device detects and amplifies the tinyelectrical changes on the skin that are causedwhen the heart muscle depolarizes duringeach heartbeat. At rest, each heart muscle cellhas a negative charge, called the membranepotential, across its cell membrane. Decreasingthis negative charge towards zero, via the influxof the positive cations, Na+ and Ca++, is calleddepolarization, which activates the mechanismsin the cell that cause it to contract.
7THE CONDUCTINGY SYSTEM• During each heartbeat, a healthyheart will have an orderlyprogression of a wave ofdepolarisation that is triggered bythe cells in the sinoatrial node,spreads out through the atrium,passes through the atrioventricularnode and then spreads all over theventricles. This is detected as tinyrises and falls in the voltage betweentwo electrodes placed either side ofthe heart which is displayed as awavy line either on a screen or onpaper. This display indicates theoverall rhythm of the heart andweaknesses in different parts of theheart muscle.
Lead Placement• By convention, we record the standardsurface ECG using 12 different recordinglead ‘directions,’ though rather confusinglyonly 10 recording electrodes on the skinare required to achieve this.• Six of these are recorded from the chestoverlying the heart – the chest orprecordial leads also called V1, V2, V3,V4, V5 and V6.• Four are recorded from the limbs – thelimb leads The limb leads are called leadsI, II, III, AVR, AVL and AVF.• It is essential that each of the 10 recordingelectrodes is placed in its correct position,otherwise the appearance of the ECG willbe changed significantly, preventingcorrect interpretation.
Normal E.C.G• A typical ECG (Limb Lead II) tracing of the cardiaccycle (heartbeat) consists of a• P wave• QRS complex• T wave• & U wave(which is normally invisiblein 50 to 75% of ECGs bcozit is hidden by the T wave and upcoming new P wave)
Lets look at how the conduction systemrelated to what we record on the ECG.• P wave: the sequential activation(depolarization) of the right and leftatria .(Atrial Repolarization mergewith QRS complex)• QRS complex: right and leftventricular depolarization (normallythe ventricles are activatedsimultaneously)• T wave ventricular repolarization• U wave: origin for this wave is notclear - but probably represents"after depolarization" in theventricles
Feature DescriptionDurationRRintervalThe interval between an R wave andthe next R wave: Normal resting heartrate is between 60 and 100 bpm0.6 to1.2sPRintervalThe PR interval is measured from thebeginning of the P wave to thebeginning of the QRS complex. ThePR interval reflects the time theelectrical impulse takes to travel fromthe sinus node through the AV nodeand entering the ventricles. The PRinterval is, therefore, a good estimateof AV node function120 to200msVAT(Ventricularactivation time)It is time required for ventriculardepolarization This is from onset of QRScomplex to the peak of R wave0.03 to0.05 secfor leftventriclesQTintervalThe QT interval is measured from thebeginning of the QRS complex to the endof the T wave. A prolonged QT interval isa risk factor for ventriculartachyarrhythmias and sudden death.Up to0.42 secin heartrate of60 bpm
Interpretation• Develop a systematic approach to reading ECGs and use it everytime.The system we will practice is:– Rate– Rhythm (including intervals and blocks)– Axis Deviation– Hypertrophy– Ischemia– P wave– PR Interval– Q wave– QRS complex– ST Segment– T wave
Rate• Before discussing how to calculateheart Rate we Should haveknowledge about ECG paper.• Paper• ECG paper is traditionally dividedinto 1mm squares. Vertically, tenblocks usually correspond to 1mV, and on the horizontal axis, thepaper speed is usually 25mm/s, soone block is 0.04s (or 40ms). Notethat we also have "big blocks" whichare 5mm on their side
Cont..• EKG paper is a grid where time ismeasured along the horizontalaxis.• Each small square is 1 mm inlength and represents 0.04seconds.• Each larger square is 5 mm inlength and represents 0.2seconds.• Voltage is measured along thevertical axis.• 10 mm is equal to 1mV involtage.
Cont..• Knowing the paper speed, its easy to workout heart rate. Its also very convenient tohave a quick way of eyeballing the rate, andone method is as follows:• Remember the sequence:300, 150, 100, 75, 60, 50• Identify an R wave that falls on the marker ofa `big block• Count the number of big blocks to the next Rwave.• If the number of big blocks is 1, the rate is300, if its two, then the rate is 150, and soon. Rates in between these numbers areeasy to `interpolate.Number ofbig boxesRate1 3002 1503 1004 755 606 50
Rhythm• This is checked by the intervals b/w two R peaks ortwo S waves is equal in all leads, the rhythm is saidto regular & if it is not. The rhythm is said to beirregular.• If rhythm is not, the rhythm is said to be irregularor irregularly irregular.• If the regularity is after regular intervals therhythm is regularly irregular,Otherwise irregularirregular.• Irregular rhythm is called Arrhythmias
Heart rate can be easily calculated from theECG strip• When the rhythm is regular, the heart rate is 300divided by the number of large squares betweenthe QRS complexes. For example, if there are 4large squares between regular QRS complexes, theheart rate is 75 (300/4=75). OR• Each second of time is represented by 250 mm (5large squares) along the horizontal axis. So if thenumber of large squares between each QRScomplex is:• 5 - the HR is 60 beats per minute.• 3 - the HR is 100 per minute.• 2 - the HR is 150 per minute.• The second method can be used with an irregularrhythm to estimate the rate. Count the number ofR waves in a 6 second strip and multiply by 10.– For example, if there are 7 R waves in a 6second strip, the heart rate is 70 (7x10=70).
Arrhythmias• These are groups of disorders.In which there is disturbance of cardiacrhythm.These are classified into following groups• 1. sinus arrhythmia• 2. Atrial arrhythmia• 3.AV junctional (nodal)arrhythmia• 4.Ventricular arrhythmia• 5.Miscellaneous(a) Accelerated conduction(b) Heart block(c) Conduction defect
Sinus Arrhythmia• Sinus arrhythmia: The normal increase in heart rate that occurs duringinspiration (when you breathe in). This is a natural response and is moreaccentuated in children than adults.• The "sinus" refers to the natural pacemaker of the heart which is called thesinoatrial (or sinus) node. It is located in the wall of the right atrium (the rightupper chamber of the heart). Normal cardiac impulses start there and aretransmitted to the atria and down to the ventricles (the lower chambers of theheart).• Sinus tachycardia refers to a fast heartbeat (tachycardia) because of rapid firingof the sinoatrial (sinus) node. This occurs in response to exercise, exertion,excitement, pain, fever, excessive thyroid hormone, low blood oxygen (hypoxia),stimulant drugs (such as caffeine), etc.• The lack of normal sinus rhythm is an arrhythmia, an abnormal heart rhythm
Bradycardia-Tachycardia Syndrome• Also known as Sick sinus syndrome
Atrial Ectopic Beats• Atrial ectopic beats (AEB) refers to a contraction of the upper heartchamber which occurs before it would be expected.• Also known as premature atrial beats, premature atrial complex(PAC), or atrial extrasystole.• As people age, extra beats tend to happen more frequently even inperfectly healthy individuals. AEB may be triggeredbystress, caffeine, smoking, and some medicines,i.e ephedrine orpseudoephedrine .• AEB may also be the result of an enlarged atria, lung disease, or theresult of reduced blood supply to that area of the heart.
Atrial tachycardia orSupraventricular tachycardia (SVT).• Supraventricular tachycardia (SVT)means that from time to timeour heart beats very fast for areason other than exercise, highfever, or stress.Types of SVT include:• Atrioventricular nodal reentranttachycardia (AVNRT).• Atrioventricular reciprocatingtachycardia(AVRT), including Wolff-Parkinson-White syndrome.
Atrial flutter.• When the heart rate is sufficiently elevated so that the isoelectricinterval between the end of T and beginning of P disappears, thearrhythmia is called atrial flutter.• The origin is also believed to involve a reentrant atrial pathway. Thefrequency of these fluctuations is between 220 and 300/min. TheAV-node and, thereafter, the ventricles are generally activated byevery second or every third atrial impulse
Atrial fibrillation.• Atrial fibrillation (AF or A-fib) is where the signal doesnt originateonly from the SA node, and so the atrium doesnt contractsimultaneously, causing an incredibly high heart rate, as well as lackof atrial systole. It is the most common cardiac arrhythmia (irregularheart beat). It may cause no symptoms, but it is often associatedwith palpitations, fainting, chest pain, or congestive heart failure.
AV Junctional (Nodal) Arrhythmia• In junctional rhythm, the sinoatrial node does not control the hearts rhythm - thiscan happen in the case of a block in conduction somewhere along the pathwaydescribed above. When this happens, the hearts atrioventricular node takes overas the pacemaker.• In the case of a junctional rhythm, the atria will actually still contract before theventricles; however, this does not happen by the normal pathway and instead isdue to retrograde conduction (conduction comes from the ventricles or from theAV node into and through the atria).• Junctional rhythm can be diagnosed by looking at an EKG: it usually presentswithout a P wave or with an inverted P wave. Retrograde P waves refers to thedepolarization from the AV node back towards the SA node
Ventricular Ectopic beats• A ventricular ectopic beat (VEB) is an extra heart-beat originating inthe lower chamber of the heart. This beat, also called a prematureventricular contraction (PVC), occurs before the beat triggered by thehearts normal function.• Ventricular ectopic beats are common and do not indicate a problemin people without heart disease. However, if a person has aorticstenosis, heart failure, or a previous heart attack, VEBs may befollowed by ventricular tachycardia and fibrillation, which can lead tosuddendeath.
Ventricular Tachycardia• Ventricular tachycardia (VT) is a fast heart rhythm thatoccurs in one of the ventricles of your heart. It is likeone electrical short circuit that races in a circle. In aVT, the heart beats with each race around the circuit atrates from 150 to 250 bpm.
Ventricular Fibrillation• VF originates from many different locations in the ventricles, eachone trying to signal the heart to beat. In this case, the heart beatsmuch faster than normal, sometimes over 300 beats a minute. Thelower chambers quiver instead of contract, and very little, ifany, blood is pumped from the heart to the rest of the body. If yourheart is in VF, you can become unconscious very quickly.
HEART Block• AV blocks– First degree block• PR interval fixed and > 0.2 sec– Second degree block, Mobitz type 1• PR gradually lengthened, then drop QRS– Second degree block, Mobitz type 2• PR fixed, but drop QRS randomly– Type 3 block• PR and QRS dissociated
First-degree AV block• First-degree AV block, or PR prolongation, is a disease ofthe electrical conduction system of the heart in which the PRinterval is lengthened beyond 0.20 seconds.• In first-degree AV block, the impulse conducting from atria toventricles through the AV node is delayed and travels slower thannormal.
2nd degree HB• Type 1 (Mobitz I/Wenckebach)• Type 2 (Mobitz II/Hay)
Type 1 (Mobitz I/Wenckebach)• progressive prolongation of the PR interval on (ECG)• consecutive beats followed by a blocked P wave (i.e., a dropped QRScomplex). After the dropped QRS complex, the PR interval resets andthe cycle repeats.• One of the baseline assumptions when determining if an individualhas Mobitz I heart block is that the atrial rhythm has to be regular. Ifthe atrial rhythm is not regular, there could be alternativeexplanations as to why certain P waves do not conduct to theventricles
Type 2 (Mobitz II/Hay)• Type 2 Second-degree AV block, alsoknown as "Mobitz II," is almostalways a disease of the distalconduction system (His-PurkinjeSystem).• Mobitz II heart block is characterizedon a surface ECG by intermittentlynonconducted P waves not precededby PR prolongation and not followedby PR shortening. The medicalsignificance of this type of AV block isthat it may progress rapidlyto complete heart block, in whichno escape rhythm may emerge.
Third-degree AV block• Also known as complete heart block, is a medical condition in which the impulsegenerated in the SA node in the atrium does not propagate to the ventricles.• an accessory pacemaker in the lower chambers will typically activate theventricles. This is known as an escape rhythm. Since this accessory pacemakeralso activates independently of the impulse generated at the SA node, twoindependent rhythms can be noted on the electrocardiogram (ECG).• The P waves with a regular P to P interval represents the first rhythm.• The QRS complexes with a regular R to R interval represent the second rhythm.The PR interval will be variable, as the hallmark of complete heart block is noapparent relationship between P waves and QRS complexes