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ECG Teaching QUB Cardiology & Cardiothoracic Surgery Society Abderrahmane El Guernaoui Learning Objectives • To comprehend the basic principlesunderlying the generation and interpretation of ECG tracings. • To learn the standard method of reading an ECG, to include identifying the rhythm, assessing the rate, and evaluatingthe axis, PR interval, QRS duration, and QT interval. • To understand the significance of ECG changes in relation to common cardiovascular conditions and diseases. • To develop proficiency in recognizing features of ST-elevation myocardial infarctions (STEMI) on an ECG. • To cultivate skills in identifying atrial fibrillation and other arrhythmias using ECG tracings. An Electrocardiogram (ECG) is a basic clinical investigation, commonly performed both in the primary and secondary care setting Irregular heartbeat, chest pain, There are several shortness of breath, high indications for performing or suspected heart valveions, Basic this investigation: problems, etc. Principles It is a useful way to rule out problems Involves 10 electrodes used to record 12 different views of your heart's electrical activityStandard Approach to Reading an ECG • Introduction • Rate & Rhythm • Axis • P Wave • PR Internal • QRS Complex • ST Segment • T Wave • Other ThingsECG Lead Positioning htpositioning/com/ecg-lead-Segments of ECG https:/ecg-library/-wave- Introduction • Patient name, DOB, any symptoms (e.g. chest pain) • ECG date and time and which in series • Check calibration o Standard paper speed: 25mm/s o Standard voltage calibration: 10mm/mV (1mV deflection at start/end of trace should be 2 large squares in height) https://images.tECG_10.png.webp?ssl=1.com/image/webp/2017/08/Introduction-to- Rate Use rhythm strip • Rate: calculate by dividing 300 by number of large squares between R peaks OR, if irregular, total R waves on ECG multiplied by 6 (ECG is 10 seconds long) o Sinus bradycardia < 60 (physical fitness, hypothermia, hypothyroidism, sinoatrial node disease, B-blockers/digoxin) o Sinus tachycardia > 100 (exercise/pain/anxiety, pregnancy, anaemia, PE, hypovolaemia, fever/sepsis, thyrotoxicosis) https://litfl.com/ecg-rate-interpretation/https://litfl.com/ecg-rate-interpretation/https://litfl.com/ecg-rate-interpretation/ https://litfl.com/ecg-rate-interpretation/ Comparison of three methods: The R wave methodis often easiestas a quick calculation Rhythm Use rhythm strip • Rhythm o Regularity: mark four R wave peaks on a plain piece of paper and move it along the trace to compare regularity against subsequent R waves (irregular: AF, ectopics, 2 degree heart block, sinus arrhythmia, atrial flutter with variable block) o Sinus rhythm or not? Look for a normal P wave before each QRS complex (no clear P waves and irregular QRS = AF; saw-tooth baseline = atrial flutter; narrow complex tachycardia with abnormal or no discernible P waves = VF, VT or rarely SVT/AF with BBB/pre-excitation; bradycardia with no P waves = sinoatrial arrest with junctional or ventricular escape rhythm; P waves present but without constant PR interval = 2 degree/complete heart block)Passmedicine.com (Atrial Fibrillation)Passmedicine.com (Atrial Flutter) Axis Axis • Use Leads I and II • Short method: QRS is normally predominantly positive in leads I and II, i.e. both point upwards • If QRS is predominantly positive in lead I and negative in lead II (i.e. pointing away from each other), there is left axis deviation – Leaving each other suits = Left axis (more electricity going to left due to: LV hypertrophy, left anterior hemiblock, LBBB, inferior MI, Wolf-Parkinson-White syndrome, VT) • If the QRS is predominantly negative in lead I and positive and in lead II (i.e. pointing towards each other), there is right axis deviation – Reaching towards each other = Right axis (more electricity going to right due to: tall and thin body type, RV hypertrophy (e.g. in PE, lung disease), left posterior hemiblock, lateral MI, Wolf- Parkinson-White syndrome) https://litfl.com/ecg-axis-interpretation/ Passmedicine.com (Axis Deviation) P Wave P Wave • Use rhythm strip • Height: should be ≤ 2 small squares (increased in right atrial enlargement, e.g. caused by pulmonary hypertension) • Morphology • Bifid (looks like an ‘m’) = P mitrale (left atrial enlargement – classically caused by mitral stenosis) • Peaked = P pulmonale (right atrial enlargement – classically in lung disease) https://litfl.com/p-wave-ecg-library/ https://litfl.com/p-wave-ecg-library/ PR Interval PR Interval • Use rhythm strip • Length:should be 3-5 small squares • Decreased: accessory conduction pathway (look for delta wave in Wolff-Parkinson-White syndrome) • Increased in AV node block (‘heart block’) • 1 degree heart block: PR > 5 small squares and regular • 2 degree heart block • Mobitz type 1 (Wenckebach): PR progressively elongates until there is failure conduction of an atrial beat (then the cycle repeats) • Mobitz type 2: constant PR intervalin the conducted beats but some of the P waves are not conducted • 2 degree heart block with 2:1/3:1/4:1 block: alternate conducted and non-conducted atrial beats (P:QRS) • Complete heart block: complete dissociation with P waves and QRS complexes. Normal atrial beats are not conducted to ventricles, which results in the ventricles self-depolarising at a much slower rate (a ‘ventricular escape rhythm’)https://litfl.com/pr-interval-ecg-library/ https://litfl.com/pr-interval-ecg-library/https://litfl.com/pr-interval-ecg-library/ https://litfl.com/pr-interval-ecg-library/ QRS Complex/Interval • Main features to consider oWidth of the complexes: Narrow vs. Broad oVoltage (height) of the complexes oSpot diagnoses: Specific morphology patterns that are important to recognize https://litfl.com/qrs- interval-ecg-library/ QRS Complex QRS Complex • Check in all leads • Q wave: note that small Q waves (<1 small square wide and <2 small squares deep) are normal in I, aVL, and V6 (LV leads) due to septal depolarisation • Pathological Q waves (established/previous full thickness MI) • Use chest leads • R wave progression: QRS complexes should progress mostly negative in V1 (i.e. dominant S) to mostly positive in V6 (i.e. dominant R). Normally the ‘transition point’ (i.e. the lead where the R and S are equal) is V3/V4. • ‘Clockwise rotation’i.e. transition point after V4 (right ventricular dilatation,usually caused by chronic lungdisease) • Dominant R wave in V1/2 (right ventricular hypertrophy,posterior MI) • Use rhythm strip (and V1 and V6 if prolonged) • Length < 3 small squares • Increased = bundle branch block • RBBB: QRS in V1 has M (RSR’) patternand QRS in V6 has W pattern– MarroW (may be caused by: right ventricularhypertrophy/cor pulmonale,PE, atrial septal defect, ischaemic disease, cardiomyopathy) • LBBB: QRS in V1 has a W patternand QRS in V6 has M pattern– WilliaM (may be caused by: aortic stenosis, ischaemic disease, hypertension, anterior MI, cardiomyopathy,conduction system fibrosis, ↑ K+) • NB: the W patternis often not fullydeveloped; the RSR’ patternmay be seen with a normal QRS length – this is partial(incomplete) bundle branch block and is of no clinical significance • Use V1 and V5/V6 • Height: look for ventricularhypertrophy • S wave depth in V1 + tallest R wave in V5/6 = >7 big squares (left ventricular hypertrophy,e.g. hypertension,AS, AR, MR, coarctation of aorta, hypertrophicobstructive cardiomyopathy) • Dominant R wave in V1 + dominant S wave in V5/V6 (right ventricular hypertrophy,e.g. pulmonaryhypertension,MS, PE). If this is present,look for other signs too, e.g. T wave inversion in right chest leads (V1-V3) and right axis deviation.https://litfl.com/qrs- interval-ecg-library/https://litfl.com/qrs- interval-ecg-library/ ST Segment ST Segment • Check in all leads – ST-elevation/depression is measured from the ‘J’ point (start at ST segment) • Elevation ≥ 1 small square (infarction; or pericarditis or tamponade if in every lead) • Depression ≥ 0.5 small square (ischaemia; or reciprocal change in posterior MI) • Morphology – ST segment is normally upwardly concave • Convex or straight ST-elevation (infarction) • Concave ST-elevation (usually other causes, e.g. early repolarisation, LVH) • Saddled ST-elevation (pericarditis, tamponade) • Downward sloping ST/’reversible tick’ (digoxin toxicity) https://litfl.com/st-segment-ecg-library/ ST Elevation https://litfl.com/st-segment-ecg-library/ ST Elevation https://litfl.com/st-segment-ecg-library/ ST ElevationST Elevation https://litfl.com/st-segment-ecg-library/Coronary T erritories Passmedicine.com https://litfl.com/st-segment-ecg-library/ ST Depression https://litfl.com/st-segment-ecg-library/ ST Depression T wave T wave • Check in all leads • TQRS complex. It represents ventricularter each repolarisation. • I(right leads) due to the angle from which they view the heart (also in V2-V3 in Afro-Caribbeanpatients). It’s almost always inverted in aVR. • Cause: ischaemia/post-MI, PE, right/left ventricular hypertrophy (right chest or lateral leads respectively), bundle branch block, digoxin treatment https://litfl.com/t-wave- • Morphology ecg-library/ • Tented (hyperkalaemia) or flat (hypokalaemia) • Biphasic (ischaemic -> up then down; hypokalaemia -> down then up)https://litfl.com/t-wave- ecg-library/ Other Things Use rhythm strips • Corrected QT interval (QTc): usually < 450ms. It is calculated by the ECG machine; if not, an online calculator can be used. It is likely prolonged if T waves extend beyond midpoint of RR interval. An increased QTc interval predisposes to polymorphic VT. • Causes of increased QTc interval: congenital syndromes, antipsychotics, sotalol/amiodarone, tricyclic antidepressants, macrolides, hypokalaemia/hypomagnesaemia/hypocalcaemia • U waves – can be normal or seen in hypokalaemia, hypothermia or with antiarrhythmics https://litfl.com/u-wave-ecg-library/ https://litfl.com/qt-interval-ecg-library/ Rhythm abnormalities Perfusion abnormalities Common Hypertrophy Fascicular blocks ECG Metabolic Pathologies Genetic conditions Other Conditions Common ECG Abnormalities: RhythmAbnormalities • AF/flutter • AF: irregular without P waves • Atrial Flutter: saw-tooth baseline (fluttering P waves) – may be regular with 2:1, 3:1 or 4:1 block, or irregular with variable block • Supraventricular tachycardias • Atrial tachycardia: regular with abnormal P waves • AV nodal re-entry tachycardia/AV re-entry tachycardia: regular, usually without discernible P waves • VT: regular, organised wavy line (broad complex is VT until proven otherwise) – MAY BE PULSED VT OR PULSELESS VT • Polymorphic VT (Torsades de Pointes): VT with varying amplitude • VF: random wavy line with no discernible P waves or QRS complexes – NO PULSES! • Asystole: flat line – NO PULSE! • Atrial ectopic: narrow QRS ± preceding abnormal P wave (resets the P wave cycle) • Ventricular ectopic: abnormal broad QRS at abnormal time (usually followed by compensatory pause) • Ventricular bigeminy (regular ventricular ectopics): abnormal premature ventricular complexes after every abnormal complex Common ECG Abnormalities: Perfusion Abnormalities • Infarction: ST-elevation (first change), T wave inversion, pathological Q waves (signify full thickness MI and develop 8-12 hours after ST elevation if myocardium is not reperfused) • STEMI criteria: ST-elevation is 2 > small in 2 adjacent chest leads or ST elevation > 1 small square in 2 adjacent limb leads or new LBBB • Ischaemia: ST-depression, new T wave inversion • Posterior (wall of LV) infarction: dominant R wave in V1/V2 with horizontal ST-depression V1-V3. o Q waves can only be seen by placing the chest leads on the patient's back • Previous infarcts: T wave inversion (persists weeks to months), pathological Q waves (permanent) Common ECG Abnormalities: Hypertrophy • Left ventricular hypertrophy: left axis deviation, dominant S wave in V1, tall R wave (>5 big squares in V5/V6), T wave inversion in lateral leads. (Sokolow-Lyon voltage criteria) • in V1, dominant S wave in V5/V6, T wave inversion in right/inferiorve chest leads (V1-3, II, III, aVF) Common ECG Abnormalities: Fascicular blocks • Any of the three conduction pathways after the bundle of His can become blocked o Right bundle branch -> RBBB pattern o Anterior fascicle of left bundle branch (i.e. left anterior hemiblock) -> marked left axis deviation o Posterior fascicle of right bundle branch (i.e. left posterior hemiblock; rare) -> marked right axis deviation • Bifascicular block is RBBB + left anterior/posterior hemiblock -> RBBB + left/right axis deviation • Trifascicular block is RBBB + left anterior hemiblock o 'Incomplete' may be either of these two patterns: ▪ Fixed block of 2 fascicles + delayed conduction in remaining fascicle = bifascicular block + 1st/2nd degree heart block ▪ Fixed block of 1 fascicle + intermittent failure of other 2 = RBBB + alternating left anterior/posterior hemiblock o 'Complete' -> complete heart block (escape rhythm) shows signs of bifascicular block ▪ block'icular heart block with 1st degree heart block is the most common pattern referred to as 'trifascicular Common ECG Abnormalities: Metabolic • Hyperkalaemia: wide flat P waves, wide bizarre QRS, tall tented T waves • Hypokalaemia: prolonged PR, depressed ST, flattened/inverted T waves, prominent U wave • Hypercalcaemia: short QT interval • Hypocalcaemia: prolonged QT interval Common ECG Abnormalities: GeneticConditions • Wolff-Parkinson White Syndrome: slurred upstroke into the QRS complex (delta wave), short PR interval, QRS complexes may be slightly broad, dominant R wave in V1 (if accessory pathway is left- sided, i.e. type A)/dominant S wave in V1 (if accessory pathway is right-sided, i.e. type B) • Hypertrophic cardiomyopathy = left ventricular hypertrophy signs + dramatic T wave inversion in lateral leads (maximal in V4 rather than V6) Other Conditions • PE – possible changes: tachycardia, right axis deviation, RA enlargement (i.e. P pulmonale), RBBB, RV dilation (i.e. dominant R in V1), RV strain (i.e. T wave inversion in right chest and inferior leads) o The 'classical' S1Q3T3 pattern (prominent S wave in lead I, and Q wave and inverted T wave in lead III) is uncommon • Pericarditis: PR depression, saddle-shaped ST elevationMCQ 1 A. Hypokalemia B. STEMI C. Pericarditis D. 1st Degree Heart Block E. Digoxin toxicity MCQ 1 - Answer • ECG features of hypokalaemia o U waves o small or absent T waves (occasionally inversion) o prolong PR interval o ST depression o long QT Passmedicine.comMCQ 2 A. Cardiac Tamponade B. Anterior STEMI C. WPWS D. Inferior STEMI E. HypercalcaemiaMCQ 2 - Answer https://litfl.com/inferior-stemi-ecg-library/MCQ 3 2. Sinus Bradycardiaon 3. WPWS 4. ST-depression MI 5. Complete Heart BlockMCQ 3 - Answer https://litfl.com/sinus-bradycardia-ecg-library/MCQ 4 1. Atrial Fibrillation 2. Atrial Flutter 3. SVT 4. ST-depression MI 5. Trifascicular BlockMCQ 4 - Answer https://litfl.com/atrial-fibrillation-ecg-library/MCQ 5 1. Acute Pericarditis 2. Atrial Flutter 3. Posterior MI 4. ST-depression MI 5. Trifascicular BlockMCQ 5 - Answer https://litfl.com/pericarditis-ecg-library/Q&A Session?Thank youSources • https://www.bhf.org.uk/informationsupport/heart-matters- magazine/medical/tests/electrocardiogram-ecg • The OSCE Revision Guide, OSCEstop, Christopher Mansbridge 2021 • https://www.theengineeringprojects.com/2017/08/introduction-to- ecg.html • https://litfl.com/