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ECG interpretation More than just squiggly lines! 29/10/2024 By Isabelle ShearsUse code CBOSCECREW24 at checkout on geekyquiz.com for 10% off OSCE flashcards, OSCE stations and knowledge bundles.The ECGs/diagrams from this session are from: Objectives Section 1 – understanding the normal shape Section 2 – how to approach a whole trace Section 3 – spotting signs that something is wrong Today is not about the pathology itself, just the traces. Next week, on Tuesday we are running a session dedicated to the history and examination of causes of palpitations! Poll ● I know nothing… yet ● I can spot a STEMI but much more and I am a bit lost ● I think I can spot the common things ● I am a pro!Understanding the normal squiggles SECTION 1 A normal ECG trace What cardiac event is happening during each of these sections?A normal ECG trace P wave A normal ECG trace P wave Atrial depolarisationA normal ECG trace PR interval A normal ECG trace PR interval The start of the P wave to the beginning of the Q wave The time for the electrical activity to get between atria and ventricles <1 big squareA normal ECG trace QRS complex A normal ECG trace QRS complex Depolarisation of the ventricles 3 separate waves that are closely related (Q, R and S)A normal ECG trace ST segment A normal ECG trace ST segment End of S to start of T Between depolarisation and repolarisation of the ventriclesA normal ECG trace T wave A normal ECG trace T wave Ventricular repolarisationA normal ECG trace QT interval A normal ECG trace QT interval Start of QRS until the end of T The time for ventricles to depolarise AND repolariseBut how do you approach it when it looks like this?How to approach a whole trace SECTION 2 Where to start? We are going to use the rule of 4s! Where to start? We are going to use the rule of 4s! ● 4 initial features ● 4 waves ● 4 intervalsThe paperWhere to start? Where to start? 1) Confirm details Where to start? 1) Confirm details - Name + DoB - Date and time of ECG Where to start? 1) Confirm details - Name + DoB - Date and time of ECG 2) Heart rate Where to start? 1) Confirm details - Name + DoB - Date and time of ECG 2) Heart rate - Normal = 60-100bpm 300/no. big squares between Rs Where to start? OR 1) Confirm details - Name + DoB No. complexes on rhythm strip X 6 - Date and time of ECG 2) Heart rate - Normal = 60-100bpm Where to start? 1) Confirm details - Name + DoB - Date and time of ECG 2) Heart rate - Normal = 60-100bpm 3) Rhythm Where to start? 1) Confirm details - Name + DoB - Date and time of ECG 2) Heart rate - Normal = 60-100bpm 3) Rhythm - Regular - Irregularly irregular - Regularly irregular Where to start? Mark the first couple of R 1) Confirm details waves along the edge of a - Name + DoB piece of paper and then move - Date and time of ECG the paper along to check they 2) Heart rate still match up - Normal = 60-100bpm 3) Rhythm - Regular - Irregularly irregular - Regularly irregular Where to start? 4) Cardiac axis Where to start? 4) Cardiac axis (the overall Normally overall is between 90 and -30 direction of electrical activity) -90 - Right or left deviation 180 0 When the overall direction is towards the lead then you get a positive deflection and vice versa 90 Where to start? 4) Cardiac axis (the overall When the overall direction is between 90* and 180* direction of electrical activity) -90 - Right or left deviation 180 0 Right axis deviation 90 Where to start? 4) Cardiac axis (the overall When the overall direction is between 90* and 180* direction of electrical activity) -90 - Right or left deviation 180 0 Right axis deviation 90 Where to start? When the overall direction is 4) Cardiac axis (the overall between 90* and 180* direction of electrical activity) -90 - Right or left deviation R is for both right aVR 1 4 and reaching II aVL 2 5 180 0 III 3 6 Right axis deviation 90 Where to start? 4) Cardiac axis (the overall Left axis deviation direction of electrical activity) -90 - Right or left deviation 180 0 When the overall direction is between -30* and -90* 90 Where to start? 4) Cardiac axis (the overall Left axis deviation direction of electrical activity) -90 - Right or left deviation 180 0 When the overall direction is between -30* and -90* 90 Where to start? 4) Cardiac axis (the overall Left axis deviation direction of electrical activity) -90 - Right or left deviation L is for left and aVR 1 4 leaving II aVL 2 5 180 0 III 3 6 When the overall direction is between -30* and -90* 90 Where to start? 4) Cardiac axis (the overall direction of electrical activity) -90 - Right or left deviation Why is reaching for RAD more reliable than leaving for LAD? 180 0 90 Where to start? 4) Cardiac axis (the overall direction of electrical activity) - Right or left deviation -90 Why is reaching for RAD more reliable than leaving for LAD? An ECG which shows ‘leaving’ 180 0 means overall electrical charge 0 and -90. LAD is only between -30 and -90. Between 0 and -30 is normal 90 Where to start? 4) Cardiac axis (the overall direction of electrical activity) 5) P waves Where to start? 4) Cardiac axis (the overall direction - Is there 1 P wave before every of electrical activity) QRS along the rhythm strip? 5) P waves - Are they the right size? (<3 small squares high) - Are they normal? Inverted? Biphasic? Where to start? 4) Cardiac axis (the overall direction of electrical activity) 5) P waves 6) PR interval Where to start? 4) Cardiac axis (the overall direction - Duration 0.12-0.2s (3-5 small of electrical activity) squares)? 5) P waves - Depression? 6) PR interval Where to start? 4) Cardiac axis (the overall direction of electrical activity) 5) P waves 6) PR interval 7) QRS complex Where to start? 4) Cardiac axis (the overall direction - Width: normal is <0.12s (3 small of electrical activity) squares). Bigger and we say ‘broad’ 5) P waves - Height: Overly tall? 6) PR interval - Shape: Delta waves (slurred 7) QRS complex upstroke)? J point right height? Where to start? 4) Cardiac axis (the overall direction of electrical activity) 5) P waves 6) PR interval 7) QRS complex 8) ST segment Where to start? 4) Cardiac axis (the overall direction of electrical activity) - Elevation? >1mm (small square) in 2 or more 5) P waves contiguous limb leads or >2 mm in 2 or more chest leads 6) PR interval - Depression? >0.5mm in 2+ 7) QRS complex contiguous leads 8) ST segment Where to start? 4) Cardiac axis (the overall direction of electrical activity) 5) P waves 6) PR interval 7) QRS complex 8) ST segment 9) T waves Where to start? 4) Cardiac axis (the overall direction of electrical activity) - Tall? >5mm in limb leads AND >10mm in chest leads 5) P waves - Inverted? Can be normal in 6) PR interval leads V1 and lead III 7) QRS complex - Biphasic? (2 peaks) 8) ST segment - Flattened? 9) T waves Where to start? 4) Cardiac axis (the overall direction of electrical activity) 5) P waves 6) PR interval 7) QRS complex 8) ST segment 9) T waves 10) QT interval Where to start? 4) Cardiac axis (the overall direction - Prolonged? Look in lead 2 of electrical activity) (rhythm strip) and measure 5) P waves from start of Q wave to end of T wave. Prolonged = >440ms in 6) PR interval men and >460ms in women. 7) QRS complex >500ms (2.5 big squares) is associated with an increased 8) ST segment risk of torsades des pointes 9) T waves 10) QT interval Where to start? 11) U waves Where to start? 11) U waves - Not a common finding - Extra wave in any individual lead (most commonly V2 or V3) - More obvious in bradycardia Where to start? 4 Initial features 4 waves (shapes/morphology) 4 intervals/segments - Patient details - P wave - PR interval - Rate - QRS wave - QRS interval - Rhythm - T waves - ST segment - Axis - U waves - QT intervalHow do we tell when something is wrong? SECTION 3Is this normal? Is this normal? This is a sinus tachy!What is the abnormality?Irregularly irregular + no p waves What could the pathology be?Atrial fibrulation (AF): disordered contraction of the atriaWhat is the abnormality?Irregularly irregular AND saw tooth flutter waves What could the pathology be? Atrial flutter – an SVT caused by re-entry of electrical activity in the atria causing rapid atrial contraction with irregular ventricular contractionWe can be extra specific by counting the amount of flutter waves between QRS complexes and putting them in a ration. This is 1:4What is the abnormality?Irregularly irregular but sinus rhythm What could this be?Sinus arrhythmia – a normal phenomenon, usually seen in young people, where reflex changes in vagal tone during different stages of the resp. cycle effect the HRWhat is the abnormality?Sinus brady + PR interval >0.2s What could the pathology be?1 degree heart block – delayed electrical conduction (but not interruption) between atria + ventricles. Doesn’t need treating.It can also look like this!What is the abnormality?Progressive prolongation of PR interval until a dropped QRS What could the pathology be? nd 2 degree heart block, Mobitz 1: ie ‘Wenckebach’. Reversable conduction block at AVN where cells progressively fatigue until fail to conduct an impulseWhat is the abnormality?Sudden drop of QRS complex without progressive PR prolongation What could the pathology be? 2nd degree heart block, Mobitz 2: ie ‘Hay block’. Intermittent non-conduction due to failure at level of Bundle of His. When they fail, they fail suddenly. nd Similarly to atrial flutter, for both categories of 2 degree heart block we can give a conduction ratio of p waves to QRS complexes. For this one it is 5:4What is the abnormality?No association between p waves and QRS complexes What could the pathology be? 3rddegree heart block – ie complete heart block. Where there is a consistent failure of conduction at the level of AVN or Bundle of HisWhat is the abnormality?Delta wave: slurring at start of broad QRS What could the pathology be?Wolff-Parkinson white: congenital accessory pathway between atria and ventricles. Predisposes to AVRT (AV re-entry tachycardia) which doesn’t slow conduction so can quickly become VF. Can be left sided (RAD) or right sided (LAD) .What is the abnormality?Broad QRS complexes throughout What could the pathology be? Left bundle branch block: the impulse runs down the right bundle to the RV then across the septum to the LV , bypassing the left bundleHow did we know the bundle branch block was on the left?L WilliaM MarroW R Do not take this too literally!What is the abnormality?Broad QRS complexes throughout What could the pathology be?Right bundle branch block: the impulse runs down the left bundle to the LV then across the septum to the RV, bypassing the right bundleWhat is the abnormality?Tombstone ST elevation in V2-V4 What could the pathology be?Anterior STEMIWe can tell which part of heart the MI occurred from the ECGWhat is the abnormality?ST elevation in leads ii, iii and aVF with reciprocal changes What could the pathology be?Inferior STEMIWhat is the abnormality?Saddle ST elevation and PR depression What could the pathology be?Acute pericarditis: Inflammation of the pericardium secondary to infection/injury/systemic disorders…What is the abnormality?R waves of alternating heights What could the pathology be?Massive pericardial effusion: This pattern occurs when the heart is swinging around in fluid filling the pericardium. It can become cardiac tamponade (fluid restricting heart function)What is the abnormality?Broad complex tachycardia What could the pathology be?Ventricular tachycardia: we can see the ventricular tachycardia which hides the atrial activity. May or may not be haemodynamically stable!What is the abnormality?1 half = prolonged QT , 2d half = PVT (polymorphic ventricular tachycardia) What is the pathology?Torsades des pointes (T dP): A specific type of PVT occurring in context of Long QT. Appears to ‘twist’ around the isoelectric lineWhat is the abnormality?Irregular fast chaos. No identifiable P waves, QRS complexes or T waves What is the pathology?Ventricular fibrulation: will be fatal if don’t act fast. Ventricles suddenly decide to contract up to 500bpm. Myocardial cells throughout the heart are not synchronised = no effective pump action. Becomes increasingly fine until becomes asystole due to depleted energy storesPremature ventricular complex (PVC) Premature ventricular complex (PVC) ● A premature broad beat that happens due to spontaneous depolarisation somewhere ● Also known as: ventricular ectopy, ventricular extrasystoles… ● Frequent ones are usually normal but may cause palpitations/’skipping a beat’ ● If associated with long QT… NOT NORMAL (may predispose torsades) ● Can trigger a re-entrant tachydysrhythmia (VT, AVNRT, AVRT…) ● Bigeminy = every other beat is a PVC ● Couplet = 2 consecutive PVCs ● Other types of ectopic beats: PACs (atrial origin), PJCs (junctional origin)Pulmonary embolism (PE) Pulmonary embolism (PE) ● S1Q3T3 – this is rare! It is when there is an S wave in lead i and an inverted Q and T in lead iii ● Sinus tachycardia ● Complete/incomplete RBBB ● RAD ● RV strain pattern – T wave inversions in the R precordial leads (V1-4) +/- inferior leads (ii, iii, aVF) if high pulmonary artery pressure Arrest rhythms Can you name them and are they all shockable? Arrest rhythms - shockable Ventricular fibrulation - Shockable Ventricular tachycardia - Shockable Arrest rhythms - NOT shockable Pulseless electrical activity (PEA) Asystole - NOT Shockable – NOT Shockable Absence of a pulse despite Absence of any electrical activity. Not electrical activity (except VT). usually completely flat, will have slight Caused by fluid loss, cardiac undulations from interference tamponade, massive PE, tension pneumothorax