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Ecg interpretation
The document provides an overview of electrocardiogram (ECG) interpretation. It discusses the key steps including assessing quality, rate, rhythm, axis, P wave, PR interval, QRS duration and morphology, ST segment, T wave, QT interval, and identifying common abnormalities. Examples of important ECG patterns are also shown, such as lateral myocardial infarction, left bundle branch block, ventricular tachycardia, and Wolff-Parkinson-White syndrome. The overall document aims to develop a structured approach for interpreting ECGs in clinical practice.
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Ecg interpretation
- 1. ECG interpretation Dr SudhirDev House Officer Dept. Of GP and Emergency Medicine
- 2. Objectives • Justify thereasons for performing an ECG • Develop a structured approach to interpreting an ECG • Practice interpreting ECGs
- 3. The ECG “The ECG(electrocardiogram) is a transthoracic interpretation of the electrical activity of the heart.”
- 4. The ECG SA node-> atrial muscle -> AV node -> bundle of His -> Left and Right Bundle Branches -> Ventricular muscle
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- 7. EKG Distributions • Anteroseptal:V1, V2, V3, V4 • Anterior: V1–V4 • Anterolateral: V4–V6, I, aVL • Lateral: I and aVL • Inferior: II, III, and aVF • Inferolateral: II, III, aVF, and V5 and V6
- 8. Why perform anECG? • It’s part of the admission bundle • Indicated by the patient’s symptoms - symptoms of IHD/MI - symptoms associated with dysrhythmias • Indicated by the patient’s examination findings - cardiac murmur
- 9. ECG Interpretation • Qualityof ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval
- 10. Quality of theECG • Patient name • Date of the ECG • Is there any interference? • Is there electrical activity from all 12 leads?
- 11. Calibration • Standard calibrationof the ECG is 10mm/mV and normal speed 25mm/sec. At this calibration, 1 miliVolt calibration signal is expected to produce a rectangle of 10 mm height and 5 mm width. • When ECG waves are tall, the R or S waves may extend into the QRS complexes above or below them. To prevent this superimposition, the whole ECG may be calibrated at 5mm/mV . LOW VOLTAGE Low voltage of the limb leads is present when the amplitude of the QRS complex in each of the three standard limb leads (I, II, and III) is <5 mm . Low voltage of all leads is diagnosed when the average voltage in the limb leads is <5 mm and the average voltage in the chest leads is <10 mm.
- 12. An example ofcorrect calibration at 10 mm/mV and speed of 25 mm/sec : The calibration signal is a rectangle making 90 degrees of angles.
- 13. ECG interpretation • Qualityof ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval
- 14. Rate • The 6Second Rule: All but very slow heart rates can be determined by counting the number of cycles that occur within 6 seconds, and then multiplying that number by 10. • The rule of 300 : 300/number of big squares between R waves • Rate is either: - Normal – Bradycardia – HR < 40bpm – Tachycardia HR > 120bpm
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- 16. Rhythm • Look for: •Are there P waves? • Are they regular? • Does one precede every QRS complex? Rythm could either be of sinus or non sinus in origin . Having P wave is sinus origin. Without P wave or buried with preceeding T wave is either Venticular or Supraventricular origin.
- 17. Axis Definition: the mean directionof electrical forces in the frontal plane ( limb leads) as measured from the zero reference point (lead 1) Normal values P wave: 0 to 75 degrees QRS complex: -30 to 90 degress T wave: QRS-T angle <45 degrees frontal or <60 degrees precordial
- 18. The Quadrant Approach •QRS up in I and up in aVF = Normal
- 19. Axis Positive in Iand II = NORMAL Positive in I and negative in II = LAD Negative in I and positive in II = RAD
- 20. D/D of RightAxis Deviation (RAD) • Differential diagnosis Right Ventricular Hypertrophy (RVH) — most common • Left Posterior Fascicular Block (LPFB) — diagnosis of exclusion • Lateral and apical MI • Acute Right Heart Strain, e.g. acute lung disease such as pulmonary embolus • Chronic lung disease, e.g. COPD • Dextrocardia • Ventricular pre-excitation (WPW) — LV free wall accessory pathway • Ventricular ectopy • Hyperkalemia • Sodium-channel blockade, e.g. tricyclic toxicity • Normal in infants and children • Normal young or slender adults with a horizontally positioned heart can also demonstrate a rightward QRS axis on the ECG.
- 21. D/D ofLeft AxisDeviation (LAD) • left ventricular hypertrophy (LVH) • Left Anterior Fascicular Block (LAFB) — diagnosis of exclusion • LBBB • inferior MI • ventricular ectopy • paced beats • Ventricular pre-excitation (WPW)
- 22. ECG interpretation • Qualityof ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval
- 23. P wave • TheP wave is the first positive deflection on the ECG • It represents atrial depolarisation Characteristics of the Normal Sinus P Wave • Morphology • Smooth contour • Monophasic in lead II • Biphasic in V1 • Axis • Normal P wave axis is between 0° and +75° • P waves should be upright in leads I and II, inverted in aVR • Duration • < 120 ms • Amplitude • < 2.5 mm in the limb leads, • < 1.5 mm in the precordial leads
- 24. P wave abnormalities CommonP wave abnormalities include: • P mitrale (bifid P waves), seen with left atrial enlargement. • P pulmonale (peaked P waves), seen with right atrial enlargement. • P wave inversion, seen with ectopic atrial and junctional rhythms. • Variable P wave morphology, seen in multifocal atrial rhythms.
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- 28. PR interval • ThePR interval is the time from the onset of the P wave to the start of the QRS complex. • It reflects conduction through the AV node. • Start of P wave to start of QRS complex • Normal = 0.12 - 0.2 seconds (3-5 small squares) • Decreased = can indicate an accessory pathway • Increased = indicates AV block (1st /2nd /3rd )
- 29. ECG interpretation • Qualityof ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval
- 30. QRS complex Main Featuresto Consider • Width of the complexes: Narrow versus broad. • Voltage (height) of the complexes. • Spot diagnoses: Specific morphology patterns that are important to recognise. • Normal = <0.12 seconds • Narrow complexes (QRS < 100 ms) are supraventricular in origin. • Broad complexes (QRS > 100 ms) may be either ventricular in origin, or may be due to aberrant conduction of supraventricular complexes (e.g. due to bundle branch block, hyperkalaemia or sodium-channel blockade)
- 31. Low Voltage QRS •Low Voltage • The QRS is said to be low voltage when: • The amplitudes of all the QRS complexes in the limb leads are < 5 mm; or • The amplitudes of all the QRS complexes in the precordial leads are < 10 mm
- 32. QRS complex • Isthere LVH? • Probably the most commonly used are the Sokolov-Lyon criteria (S wave depth in V1 + tallest R wave height in V5-V6 > 35 mm). >35mm is suggestive of LVH
- 33. Q waves • Qwaves are allowed in V1, aVR & III • Pathological Q waves can indicate previous MI
- 34. ECG interpretation • Qualityof ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval
- 35. ST segment • TheST segment is the flat, isoelectric section of the ECG between the end of the S wave and the beginning of the T wave. • It represents the interval between ventricular depolarisation and repolarisation. • The most important cause of ST segment abnormality (elevation or depression) is myocardial ischaemia / infarction. • ST depression (upsloping, horizontal and downsloping) - downsloping or horizontal = ABNORMAL • ST elevation - infarction - pericarditis (widespread)
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- 38. T wave • Small= hypokalaemia • Tall = hyperkalaemia • Inverted/biphasic = ischaemia/previous infarct • Hyperkalemia: Potassium reduces myocardial excitability, with depression of pacemaking and conducting tissues. • K+ >5.5 meq/l is a/w repolarization abnormalities causing peaked T waves (earliest sign of hyperkalemia) • K+>6.5 a/w progressive paralysis of artia , ECG shows wide and flat P wave, incerase PR and P wave eventually dissapear. • K+ more than 7 causes conduction abnormalities and bradycardia and eventually asystole.
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- 42. QT interval • Startof QRS to end of T wave • Needs to be corrected for HR • Normal QTc = < 400ms • Long QT can be genetic or iatrogenic
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- 44. Blocks AV blocks First degreeblock PR interval fixed and > 0.2 sec Second degree block, Mobitz type 1 PR gradually lengthened, then drop QRS Second degree block, Mobitz type 2 PR fixed, but drop QRS randomly Type 3 block PR and QRS dissociated
- 45. Some important ECGexamples
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- 47. Inferolateral MI ST elevationII, III, aVF ST depression in aVL, V1-V3 are reciprocal changes
- 48. Anterolateral / InferiorIschemia LVH, AV junctional rhythm, bradycardia
- 49. Left Bundle BranchBlock Monophasic R wave in I and V6, QRS > 0.12 sec Loss of R wave in precordial leads QRS T wave discordance I, V1, V6 Consider cardiac ischemia if a new finding
- 50. Right Bundle BranchBlock V1: RSR prime pattern with inverted T wave V6: Wide deep slurred S wave
- 51. First Degree HeartBlock, Mobitz Type I (Wenckebach) PR progressively lengthens until QRS drops
- 52. Supraventricular Tachycardia Narrow complex,regular; retrograde P waves, rate <220 Retrograde P waves
- 53. Right Ventricular MyocardialInfarction Found in 1/3 of patients with inferior MI Increased morbidity and mortality ST elevation in V4-V6 of Right-sided EKG
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- 55. Prolonged QT QT >450 ms Inferior and anterolateral ischemia
- 56. Second Degree HeartBlock, Mobitz Type II PR interval fixed, QRS dropped intermittently
- 57. Acute Pulmonary Embolism SIQIIITIIIin 10-15% T-wave inversions, especially occurring in inferior and anteroseptal simultaneously RAD
- 58. Wolff-Parkinson-White Syndrome Short PRinterval <0.12 sec Prolonged QRS >0.10 sec Delta wave Can simulate ventricular hypertrophy, BBB and previous MI
- 59. Hypokalemia U waves Can alsosee PVCs, ST depression, small T waves
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Editor's Notes
- #5 Cardiac conducting system
- #10 It’s vital to have a system in place to interpret the ECG.
- #11 Small square 0.04s; Large square 0.2s
- #14 It’s vital to have a system in place to interpret the ECG.
- #17 Can use lead II
- #18 The normal axis is around 60 degrees.
- #23 It’s vital to have a system in place to interpret the ECG.
- #24 Not very useful signs.
- #29 Short PR interval can be accessory pathway or can be normal
- #30 It’s vital to have a system in place to interpret the ECG.
- #35 It’s vital to have a system in place to interpret the ECG.
- #39 Tall = can be normal young man
- #40 T wave more than 10mm size= hyperkalemia
- #43 Long QT syndrome. Amiodarone, sotalol.
- #44 Long QT syndrome is associated with Torsades de pointes
- #47 Resiprocal: Reciprocal changes are simple the opposite deflection in an opposing lead, for example a posterior infarction causing ST depression in the anterior leads.
- #52 Mobitz type I, RBBB, LVH