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ECG Anya Olsen and Olivia Owen STRUCTUREDAPPROACHTO ECG INTERPRETATION • Check patient details and machine settings • Rhythm • Rate • P wave • PR interval • QRS complex • QT interval • ST segment • T wave • Axis • Take the history into consideration • Give your differential diagnosis CHECK DETAILS • Correct patient • Correct ECG:date and time • Machine settings :25mm/s,10mm=1mV RHYTHM • Count number of squares between QRS complexes • Regular:same number between all complexes • Irregularly irregular:completely disorganized • AF • Ectopic beats • Some types of heart block e.degree • Regularly irregular:recurrent pattern of irregularity • Mobitz I heart block (more on this later!) RATE • If regular rhythm • 300/(number of large squares between R waves) • If irregular rhythm • (Number of QRS complexes on a 10 second strip) x 6 PWAVE • Usually less than 0.25mV (2.5mm) • Peaked P waves (.5mm) = P-Pulmonale.Seen in right atrial hypertrophy • Usually,P wave preceding every QRS complex • AF:irregularly irregular rhythm and fibrillating baseline (no P waves) • Heart blocks:various types! • SVT/VT:tachycardia,no P waves,(narrow/broad QRS) • Ventricular ectopic:random broad QRS complex not preceded by P wave • (Abnormal) Bifid P waves? • P-Mitrale:left atrial hypertrophyNORMAL ECG ATRIAL FIBRILLATION • No P waves • Irregularly irregular rhythm • Fibrillating baseline • Can have a fast or slow ventricular response (brady or tachycardia or normal!) • Narrow QRS usually ATRIAL FLUTTER • ECG • Classical‘sawtooth appearance’ of flutter waves • Rapid atrial rate (300 bpm) • Can have a 1:1,2:1,3:1,4:1 block (i.e.,1/2/3/4 P waves per QRS complex) (regular) • Previous example had a variableAV block (irreg irreg) but example on top right has 3:1 (regular,100 bpm) SINUSTACHYCARDIA • Rate > 100 • Regular • P waves present before each QRS PR INTERVAL (BEGINNING OF PWAVE TO BEGINNING OF QRS COMPLEX) • Normally between 0.12 and 0.2 seconds (3-5 small squares) • Short PR interval (<0.12s) • WPW syndrome (accessory pathway doesn’t introduce a pause intro transmission of impulse) • Long PR interval • 1 degree heart block:consistent PR interval that is more than 0.2s nd • 2 degree heart block – Mobitz I;PR interval gets progressively longer until a QRS complex is dropped,and the cycle starts again nd • 2 degree heart block – Mobitz II:no progressive prolongation of PR interval (PR interval mostly normal) but with occasionally dropped QRS complexes • Can be“fixed ratio block” e.g.,3:1,4:1 • 3 degree (complete) heart block – no relationship between P waves and QRS complexes QRS COMPLEX (1) • Normal duration is <0.12s (less than 3 small squares) • Q wave is usually no more than 2mm deep and <0.04s (1mm) • Voltage of QRS complex should be more than 0.5mV (5mm) • Left ventricular hypertrophy:Sokolow-Lyon index • Right ventricular hypertrophy QRS COMPLEX (2):WIDE QRS (>0.12S / 3 SMALL SQUARES) • Sinus rhythm with wide QRS • Conduction abnormalities:RBBB or LBBB • Remember: WiLLiaM MoRRoW • LBBB: W inV1 and M inV6 • RBBB:M inV1 andW inV6 • Wide QRS,tachycardia and no P waves • VT • Random wide complex QRS not preceded by a P wave in an otherwise normal strip • Ventricular ectopic QRS COMPLEX (3):PATHOLOGICAL Q WAVES • Significant Q waves are deeper than 2mm or longer than 0.04s in duration (1mm) • Can be present a couple of hours/days after an acute MI • Can indicate PE (SIQIIITIII) QRS COMPLEX (4):LOWVOLTAGE QRS • QRS complex less than 0.5mV (5mm) • Hypothyroidism • Myocarditis • Pericarditis • Pericardial effusion QRS COMPLEX (5):LVH/RVH • RVH • Dominant R wave inV1 • TWI inV1-3 orV4 • Deep S wave inV6 • LVH:Sokolow Lyon index • R wave inV5/6 (whichever is bigger) + S wave inV1 • If over 35mm,indicates LVH • (Another method:R wave inV5>25mm) SUPRAVENTRICULARTACHYCARDIA • (technically,sinus tachy,AF,atrial flutter are types of SVT but should be able to identify and name these separately) • SVT:tachycardia,no P waves,narrow QRS complex VENTRICULARTACHYCARDIA • Tachycardia • No P waves • Broad QRS • Often can’t seeT waves either VENTRICULAR FIBRILLATION • Rapid • Chaotic deflections • Variable amplitude • No P waves,QRS complexes orT waves can be identified QT INTERVAL • QTc is usually reported at the top • Normal is under 430 in men,under 450 in women • Causes of long QT • Inherited:Jervell-Lange Nielson,RomanoWard syndrome • Medications:amiodarone,sotalol 1a antiarrhythmics,TCAs,SSRIs (especially citalopram), ondansetron,methadone,chloroquine,haloperidol,terfenadine,erythromycin • Conditions:SAH,hypothermia,acute MI,myocarditis,hypokalaemia,hypomagnesaemia, hypophosphataemia • Significance of long QT interval:can lead toVT/torsades,can be associated with syncope sudden cardiac death (long QT syndrome)MILLION -DOLLAR QUESTION ST SEGMENT • ST depression = ischemia • ST elevation = infarction • STEMI criteria • in 2 ofV2-V3 • Men under 40:2.5mm • Men over 40:2mm • Women:1.5mm • In all other leads:1mm • New LBBB:treat as STEMI (LBBB = new unless proven otherwise!) TWAVE • Usually less than 0.5mV (5mm) in limb leads and 1mV (10mm) in praecordial leads • Normally asymmetrical with slurred upstroke and rapid downstroke • T wave inversion occurs in ischemia and infarction (abnormal in I,II,V4-V6) • In MI:tallT waves > flatT waves > invertedT waves (over time) CASE 56-year-old man presents toA&E with a 40-minute history of central chest pain (came on at rest,no relived by GTN spray,no radiation,associated nausea) PMH:stable angina for the past 6 years,COPD O/E:clammy,in obvious pain,remainder of examination unremarkable CASE A 47-year-old man presents toA&E with severe SOB,clamminess and nausea. PMH:type 2 diabetes,HTN,intermittent claudication An ECG is performed: CASE A 76-year-old lady presents toA&E with central constricting chest pain,radiating to her jaw and left arm.You review her bloods and ECG: Haemoglobin 122 g/l Men:135- 180 g/l Women: 115-160 g/l Mean cell 97 fl 82-100 fl volume Platelets 3769* 159-400 * 10 /l 10 /l 9 White blood 8.3 * 10 /l 4.9-11.0 * cells 10 /l Troponin 473 ng/L <14 ng/LLOCATINGAN MI ECG changes seen in Coronary artery Anteroseptal V1-V4 Left anterior descending Inferior II,III,aVF Right coronary Anterolateral V4-6,I,aVL Left anterior descending or left circumflex Lateral I,aVL +/-V5-6 Left circumflex Posterior •Changes inV1-3 Usually left circumflex,also right coronary Reciprocal changes of STEMI are typically seen: horizontal ST depression •tall,broad R waves •uprightT waves •dominant R wave inV2 Posterior infarction is confirmed by ST elevation and Q waves in posterior leads (V7-9)LOCATINGAN MI STEMI / NSTEMI / UNSTABLEANGINA STEMI NSTEMI Unstable angina ECG ST elevation/ new +/- (ST depression,+/- (ST depression, LBBB TWI,pathological TWI,pathological Q waves) Q waves) +/- (ST depression, If ECG changes are TWI,pathological present,they are Q waves) transient Troponin Raised Raised NormalAXIS DETERMININGTHEAXIS (1) • Lots of ways to work it out https://litfl.com/ecg-axis-interpretation/ • Quadrant method:use I and aVF • Three lead analysis:use I,II and aVF • Isoelectric lead method QUADRANT METHOD ** Need to evaluate using lead II If positive,axis is normal/ If negative,LAD 1 2 A. 1 = normal,2 = LAD B.1 = LAD,2 = RAD C.1 = normal,2 = RAD D. 1 = RAD,2 = normal Recommended resources for axis E.1 = LAD,2 = extreme axis deviation 1.https://litfl.com/ecg-axis-interpretation/ 2.Quiz:https://ecg.utah.edu/test/1QUESTIONS?12345FEEDBACK FORMS
