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Data Interpretation Series: ECG Dr. Lily Wenyi Cai General Surgery FY1Social Medias Learning Objectives • Understand the electrophysiology of an ECG trace • Be able to present a 12-lead ECG • Understand the basics of a normal ECG components • Be able to recognize common arrhythmia patterns However, this tutorial is NOT for • Comprehensive management for ECG abnormalitiesECG 1 Question Normal ECGECG 1 ECG Physiology • SA node is the heart’s natural pacemaker • Electrical impulse starts in SA node • Then travels to the AV node • AV node delays the impulse by 0.1s • The impulse then travels down the ventriclesECG 1 Standard ECG Trace depolarisation depolarisation Ventricular repolarisation ECG 1 Components of a ECG • Patient details • Date and Time • Rate and Rhythm • Cardiac Axis • P wave • PR interval • QRS interval • ST segment • QT interval ECG 1 How to Present a 12-lead ECG? Remember, in OSCE, ECG is a tick-box exercise! Always start off by stating the patient details e.g. crushing central chest pain…”0 year old gentleman, which was taken 6pm on 12/09/2021. The indication for this ECG is State the obvious abnormality “The obvious abnormality is there is ST elevation in leads II, III and aVF.” Then go through each of the component of the ECG systematically “HR is 80 bpm; There is sinus rhythm throughout Cardiac axis is normal P wave is present and normal PR interval is normal QRS has a narrow complex ST segment in leads … shows no abnormalities T wave is normal QT interval is normal…”ECG 1 How to determine heart rate? Count the large squares between peak of QRS complexes large squares between R-R intervalthe equation 300/no. ofECG 1 How to determine rhythm? • Regular sinus rhythm = QRS follows every P wave + PP intervals are equal • Regularly irregular sinus rhythm = QRS follows every P wave + PP intervals are unequal • Irregularly irregular rhythm = P wave is not present before QRS i.e. AFECG 1 How to determine cardiac axis? Lead I Lead aVF Normal axis Going towards the same direction Right axis each otherrds deviation (RIGHT for each other) Left axis Going away from deviation each other (LEFT each other) PR, QRS and QT ECG 1 PR interval 0.12-0.20 seconds (3-5 small sqs) QRS interval 0.08-0.10 seconds (2-2.5 small sqs) QT interval 0.4-0.44 seconds (10-11 small sqs) Bazzet equation for corrected QT (cQT=QT/Sq(RR interval)ECG 2 Atrial Fibrillation ECG 2 Atrial Fibrillation • AF can be paroxysmal, persistent or permanent • Risk factors • Vascular: hypertension, ischaemic heart disease, valve pathologies • Non-vascular: hyperthyroidism, exposure to stimulants (e.g. caffeine), lung diseases • Presentation • Symptoms: palpitation; breathlessness; syncope; chest pain; dizziness • Signs: irregularly irregular pulse • Management • Most important thing: determine if the patient is haemodynamically stable • If they are not: direct cardioversion immediately • If they are: proceed with rate control (e.g. bisoprolol) if tachycardia and determine the need to anti-coagulate (CHA2DS 2VASc) • Rhythm can be attempted to convert back to normal after 4-6 weeks of anticoagulation.ECG 3 STEMI from V1-V5, I and aVLECG 4 ST depression in lead I, II, V-4-6 ECG 3&4 Acute Coronary Syndrome Possible ECG changes in ACS Leads affected • T wave inversion (apart from lead aVR) • New-onset LBBB Right coronary artery Inferior leads: II, III, aVF • NSTEMI • STEMI Presentation • Central chest pain; N+V; radiation of pain to left side; LOC Immediate Management Left anterior descending Anterior leads: chest artery leads V1-4 • Pain relief + anti-emetics: Morphine IV 10mg + Metoclopramide IV 10mg • Oxygen: if oxygen saturation is low • Double antiplatelets: Aspirin 300mg + Clopidogrel 300mg/Ticagrelol 180mg • Fondaparinux 2.5mg SC (unless PCI planned) Left circumflex artery Lateral leads: V5-6, I, aVLECG 5 First Degree Heart BlockECG 6 Second Degree Heart Block: Mobitz Type I / Wenckebach PhenomenonECG 7 Second Degree Heart Block: Mobitz Type IIECG 8 Complete / Third Degree Heart BlockECG 5-8 Heart Blocks • Definition: a delay in the transmission of electrical impulse from the atria to the ventricles • Presentation • Dyspnoea; fatigue; syncope (Adams-Stokes attack) Cardiac Infiltrative/inflamm Infectious Medications atory Ischaemic heart Sarcoidosis Rheumatic fever Calcium channel disease Amyloidosis Lyme disease blockers Cardiomyopathies SLE Beta-blockers Endocarditis AdenosineECG 5-8 Heart Blocks Types of heart blocks Treatment First degree heart block Usually a benign entity – no treatment needed Mobitz type I / Still a benign entity Wenckebach Asymptomatic – does not require treatment Symptomatic – change medication; atropine Mobitz type II Requires urgent permanent pacing Third degree heart block /Medical emergency – requires a pacemaker +/- complete heart block ICDECG 9 Ventricular Tachycardia ECG 9 Cardiac Arrest Rhythms • 4 possible cardiac rhythms cardiac arrest • Ventricular fibrillation (VF): disorganized electrical activities • Ventricular tachycardia (VT): organized electrical activities • Pulseless electrical activity (PEA): Normal trace without a pulse • Asystole: flatline • Shockable rhythm: VF and VT • Non-shockable rhythm: PEA and asystole • Commence CPR • Reversible causes of cardiac arrest • 4 Ts: Tension pneumothorax; Tamponade; Toxins; Thrombosis • 4 Hs: Hypovolaemia; Hypoxia; Hypokalaemia/hypercalcaemia; HypothermiaECG 10 Supra-ventricular tachycardiaECG 10 Supra-ventricular tachycardia Atrioventricular Reentry Atrioventricular Nodal Reentry Tachycardia (AVRT) Tachycardia (AVNRT) Accessory pathway bypasses Accessory pathway re-enters the the AV node to cause AV node causing ventricular premature ventricular excitationexcitation Wolff-Parkinson-White syndrome (Bundle of Kent) O O F Feedback & Instagram + 3C N Please complete feedback to receive slides! 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