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Basics in Electro Cardio Gram Interpretation – Part 1 Dr Anidu Pathirana MBBS(Col), MD(Col.), MRCP(UK), FCCP What is Electro Cardio Gram ? Tracing of heart’s electrical activity 2 Electrical activity of cells Resting membrane potential – 70 mV 3 Electrical activity of cells Depolarization Action potential 4 EXCITABILITY Electrical activity of Nerve & Muscle SELF- PROPAGATION 5 Electrical & Mechanical activity of heart Automaticity Rhythmicity Conductivity Excitability Contractility Organizational hierarchy 6 Electro Mechanical Disssociation Look at the patient first, Look at the ECG afterwards 7 Recording of an ECG: History Pick up electrical activity (depolarization wave) from outside. By placing 2 electrodes on patient either side of the heart 8 Recording of an ECG: Contact electrodes n=10 9 How does the ECG works ? Electrodes are paired (one positive and other negative)to sense the change in voltage between them. Such a pair is called lead. 12- lead ECG 11 Leads look at the heart in two planes & from different directions 12 Recording vectors Electrical impulse travels towards positive gives a positive deflection Electrical impulse travels away from positive electrode gives a negative deflection 13 ECG recording paper 14 Recorded ECG 15 Recording of an ECG 16 Normal ECG complex P wave- atrial depolarization QRS together in a complex ventricular depolarization T wave- ventricular repolarization U wave- inter ventricular septum repolarization 17 Normal ECG complex 18 Durations & Intervals 19 Normal intervals 20 Systematic reading Check the details: identification, date & time Calibration Rhythm: Normal Sinus Rhythm or not Rate Cardiac axis P-wave, PR-interval, QRS complex, ST segment, QT- interval, T & U – wave Other signs- Ischemia, infraction, hypertrophy Compare with previous ECGs 21 Calibration Calibration 22 Paper speed 23 Rhythm: Normal sinus rhythm or Not Every P wave is followed by QRS, every QRS preceded by P; Rate anywhere between 60-99; PR interval 3-5 squares; always upright in lead I & II 24 How to recognize an arrhythmia? 1. Is there any electrical activity? 2. Are there any recognizable complexes? 3. What is the ventricular (QRS) rate? 4. Is the QRS rhythm regular or irregular? 5. Is the QRS complex width normal or prolonged? 6. Is atrial activity present? 7. How is atrial activity related to ventricular activity? 25 How to recognize an arrhythmia? 2. Are there any recognizable complexes? 3. What is the ventricular (QRS) rate? 4. Is the QRS rhythm regular or irregular? 5. Is the QRS complex width normal or prolonged? 6. Is atrial activity present? 7. How is atrial activity related to ventricular activity? 26 Rhythm recognition: Q1-Is there any electric activity? No – Check leads, electric connection No – Check gain 27 Rhythm recognition: Q1-Is there any electric activity? No- Asystole Yes- but only P waves called P wave asystole Yes- Go to Q2 28 How to recognize an arrhythmia? 1. Is there any electrical activity? 3. What is the ventricular (QRS) rate? 4. Is the QRS rhythm regular or irregular? 5. Is the QRS complex width normal or prolonged? 6. Is atrial activity present? 7. How is atrial activity related to ventricular activity? 29 Rhythm recognition: Q2-Are there any recognizable complexes? No- most likely ventricular fibrillation Yes- Q3 30 How to recognize an arrhythmia? 1. Is there any electrical activity? 2. Are there any recognizable complexes? 4. Is the QRS rhythm regular or irregular? 5. Is the QRS complex width normal or prolonged? 6. Is atrial activity present? 7. How is atrial activity related to ventricular activity? 31 Rhythm recognition: Q3- What is the ventricular rate? Look at lead II, rhythm strip. Determine distance between one RR interval. Use one of the formula, 32 Rate Calculation: An example 33 Rate Calculation: In an irregular rhythm Count number of beats in a 6 sec strip and multiply by 10 34 Classification of Arrhythmia Brady arrhythmia Rate <60/min. Tachy arrhythmia Rate > 100/min. 35 How to recognize an arrhythmia? 1. Is there any electrical activity? 2. Are there any recognizable complexes? 3. What is the ventricular (QRS) rate? 5. Is the QRS complex width normal or prolonged? 6. Is atrial activity present? 7. How is atrial activity related to ventricular activity? 36 Rhythm recognition: Q4- Is the rhythm regular or irregular? Look at lead II. Use a paper strip to map out consecutive beats. Measure RR interval for ventricular rhythm & PP interval for atrial rhythm 37 Rhythm recognition: Q4- Is the rhythm regular or irregular? If regular : Go to Q5 38 Rhythm recognition: Q4- Is the rhythm regular or irregular? If irregular- Decide if occasionally irregular or totally irregular or irregular in a cyclical pattern Irregularly irregular rhythm 39 Rhythm recognition: Q4- Is the rhythm regular or irregular? Regularly irregular Sinus arrhythmia P wave morphology & axis normal, PP interval >0.16 sec or 10% 40 Sinus Pause In case SA node fails- if failure is brief and recovery is prompt result is only a missed beat. 41 Atrial Escape If recovery is delayed and some other focus assumes pacing function resulting in an escape beat or escape rhythm. Other atrial foci act as a pacemaker, rate = 60-80bpm, P waves have abnormal axis and looks different but QRS complex appears exactly the same 42 Junctional Escape AV node as a pacemaker, rate 40-60bpm,P waves are inverted, appear before after or hidden within QRS, QRS is normal 43 Ventricular Escape Ventricular myocardium as pacemaker, depolarization wave spreads slowly via myocardium and not via His bundle or its branches 44 Atrial Premature Beat Sometimes an irritable focus could dominate over SA node An irritable focus in one of the atria. ABP has a different looking P wave while QRS complex appears normal If non conducted would deform the preceding T wave 45 Junctional Premature Beat An irritable focus at AV junction, P wave is usually inside QRS and not visible. If visible, it is negative in lead II and positive in aVR 46 Premature Ventricular Complexes Common. Heartbeat is initiated at ventricle. No P waves. May produce bizarre looking T wave 47 How to recognize an arrhythmia? 1. Is there any electrical activity? 2. Are there any recognizable complexes? 3. What is the ventricular (QRS) rate? 4. Is the QRS rhythm regular or irregular? 6. Is atrial activity present? 7. How is atrial activity related to ventricular activity? 48 Rhythm recognition: Q5-Is QRS complex width normal or prolonged? QRS width normal <0.12 sec / 3 small squares Narrow Complex (Originate above the bifurcation of bundle of His) QRS wider than 0.12 sec / 3 small squares Broad Complex(ventricular or supra ventricular with aberrant conduction) 49 Rhythm recognition: Q5-Is QRS complex width normal or prolonged? Narrow complex regular tachycardia Broad complex regular tachycardia 50 >3 consecutive wide QRS, capture and fusion beats How to recognize an arrhythmia? 1. Is there any electrical activity? 2. Are there any recognizable complexes? 3. What is the ventricular (QRS) rate? 4. Is the QRS rhythm regular or irregular? 5. Is the QRS complex width normal or prolonged? 7. How is atrial activity related to ventricular activity? 51 Rhythm recognition: Q6- Is atrial activity present? Yes : Normal P-wave ( axis +15 to +75) 52 Rhythm recognition: Q6- Is atrial activity present? Yes : Abnormal P-wave 53