Ecg usm
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This document provides a tutorial on electrocardiography (ECG) including: - The basics of ECG calibration and electrical impulse propagation. - Descriptions of the P wave, QRS complex, ST segment, T wave, and other ECG components. - Identification of abnormalities including hypertrophy, infarction, arrhythmias, and axis deviations. - Guidance on interpreting ECG findings related to conditions like myocardial infarction, hypertrophy, and conduction blocks. - Algorithms for managing cardiac arrest and arrhythmia rhythms. - Recommended resources for further ECG education.
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Ecg usm
- 1. Tutorial in ECG Dr. Chew Keng Sheng Emergency Medicine Universiti Sains Malaysia http://emergencymedic.blogspot.com
- 2. The Basics • Standard calibration – 25 mm/s – 0.1 mV/mm • Electrical impulse that travels towards the electrode produces an upright (“positive”) deflection relative to the isoelectric baseline
- 3. Vertical and horizontal perspective of the ECG Leads Leads Anatomical II, III, aVF Inferior surface of heart V1 to V4 Anterior surface of heart I, aVL, V5, and V6 Lateral surface of heart V1 and aVR Right atrium
- 4. Location of MI and Affected Coronary Arteries Location of MI Affected Artery Lateral Left circumflex Anterior LAD Septum LAD Inferior RCA Posterior RCA Right Ventricle RCA
- 5. Right Sided & Posterior Chest Leads
- 6. Sinus Rhythm • The P wave is upright in leads I and II • Each P wave is usually followed by a Q • The heart rate is 6099 beats/min
- 8. Instant Recognition of Axis Deviation
- 9. Cardiac Axis Normal Axis Right Axis deviation Left Axis Deviation Lead I Positive ↑ Negative ↓ Positive ↑ Lead II Positive ↑ Positive ↑ Negative ↓ Lead III Positive Positive Negative
- 11. P wave • Always positive in lead I and II in NSR • Always negative in lead aVR in NSR • < 3 small squares in duration • < 2.5 small squares in amplitude • Commonly biphasic in lead V1 • Best seen in leads II
- 12. Right Atrial Enlargement • Tall (> 2.5 mm), pointed P waves (P pulmonale
- 13. Left Atrial Enlargement • Prominent terminal P negativity (biphasic) in lead V1 (i.e., "Pterminal force") duration >0.04s, depth >1 mm
- 14. • Notched/bifid (‘M’ shaped) P wave (P ‘mitrale’) in limb leads with the interpeak duration > 0.04s (1 mm) Left Atrial Enlargement
- 15. P Pulmonale and P Mitrale
- 17. RAH and LAH Right Atrial Hypertrophy Left Atrial Hypertrophy
- 18. Short PR Interval • WPW (Wolff- Parkinson-White) Syndrome • Accessory pathway (Bundle of Kent) allows early activation of the ventricle (delta wave and short PR interval)
- 19. QRS Complexes • Non-pathological Q waves are often present in leads I, III, aVL, V5, and V6 • The R wave in lead V6 is smaller than the R wave in V5 • The depth of the S wave, generally, should not exceed 30 mm • Pathological Q wave > 2mm deep and > 1mm wide or > 25% amplitude of the subsequent R wave
- 21. RVH Changes • A tall positive (R) wave – instead of the rS complex normally seen in lead V1 – an R wave exceeding the S wave in lead V1 – in adults the normal R wave in lead V1 is generally smaller than the S wave in that lead • Right axis deviation (RAD) • Right ventricular "strain" T wave inversions
- 22. Conditions with Tall R in V1
- 23. Right Atrial and Ventricular Hypertrophy
- 24. COPD
- 25. Left Ventricular Hypertrophy • Sokolow & Lyon Criteria (Am Heart J, 1949;37:161) – S in V1+ R in V5 or V6 > 35 mm • An R wave of 11 to 13 mm (1.1 to 1.3 mV) or more in lead aVL is another sign of LVH • Others: Cornell criteria (Circulation, 1987;3: 565-72) – SV3 + R avl > 28 mm in men – SV3 + R avl > 20 mm in women
- 27. Hypertrophy Strain Pattern vs ACS
- 28. ST Segment • Normal ST Segment is flat (isoelectric) – Same level with subsequent PR segment • Elevation or depression of ST segment by 1 mm or more, measured at J point IS ABNORMAL • “J” (Junction) point is the point between QRS and ST segment
- 29. Variable Shapes Of ST Segment Elevations in AMI Goldberger AL. Goldberger: Clinical Electrocardiography: A Simplified Approach. 7th ed: Mosby Elsevier; 2006.
- 30. T wave • The normal T wave is asymmetrical, the first half having a more gradual slope than the second half • The T wave should generally be at least 1/8 but less than 2/3 of the amplitude of the corresponding R wave • T wave amplitude rarely exceeds 10 mm • Abnormal T waves are symmetrical, tall, peaked, biphasic or inverted.
- 31. T wave • As a rule, the T wave follows the direction of the main QRS deflection. Thus when the main QRS deflection is positive (upright), the T wave is normally positive. • Other rules – The normal T wave is always negative in lead aVr but positive in lead II. – Left-sided chest leads such as V4 to V6 normally always show a positive T wave.
- 32. QT interval • QT interval decreases when heart rate increases • A general guide to the upper limit of QT interval. For HR = 70 bpm, QT<0.40 sec. – For every 10 bpm increase above 70 subtract 0.02 sec. – For every 10 bpm decrease below 70 add 0.02 sec • As a general guide the QT interval should be 0.35- 0.45 s, and should not be more than half of the interval between adjacent R waves (R-R interval).
- 33. QT Interval
- 34. Long QT Syndrome
- 35. QT Interval • The QT interval increases slightly with age and tends to be longer in women than in men. • Bazett's correction is used to calculate the QT interval corrected for heart rate (QTc): QTc = QT/ Sq root [R-R in seconds]
- 36. U wave • Normal U waves are small, round, symmetrical and positive in lead II, with amplitude < 2 mm (amplitude is usually < 1/3 T wave amplitude in same lead) • U wave direction is the same as T wave direction in that lead • More prominent at slow heart rates and usually best seen in the right precordial leads. • Origin of the U wave is thought to be related to afterdepolarizations which interrupt or follow repolarization
- 37. Calculation of Heart Rate • Method 1: Count the number of large (0.2- second) time boxes between two successive R waves, and divide the constant 300 by this number OR divide the constant 1500 by the number of small (0.04-second) time boxes between two successive R waves. • Method 2: Count the number of cardiac cycles that occur every 6 seconds, and multiply this number by 10.
- 38. Calculation of Heart Rate
- 39. Question • Calculate the heart rate
- 40. RBBB and LBBB • RBBB = MaRroW • LBBB = WiLLiaM
- 42. Cardiac Arrest & Peri-arrest Rhythms • Cardiac Arrest – Shockable • VF, Pulseless VT – Non Shockable • Asystole, PEA • Peri arrest rhythms – Tachyrrhythmias – Bradyarrhythmias Drugs to control rate Drugs to revert the rhythms
- 43. Note that by this time, if 3rd shock is required, it is the DRUG →SHOCK→ CPR sequence. It is the same sequence thereafter The drugs to be given at this stage are vasopressors Cardiac Arrest
- 44. After the 3rd sequence and giving adrenaline/vasopressin, consider giving antiarrhythmics like amiodarone for VF or magnesium for torsades de pointes. The sequence is still the same DRUG→SHOCK→ CPR. At any time, if rhythm becomes non-shockable, follow the non-shockable algorithm Cardiac Arrest
- 45. For cardiac arrest, the first thing to know is whether the rhythm is shockable or not shockable. In periarrest rhythms (bradyarrhythmias and tachyarrhythmias, the first thing to know is whether it STABLE or NOT STABLE
- 46. When The Arrhythmias Is Unstable Four main signs 1. Signs of low cardiac output – systolic hypotension < 90 mmHg, altered mental status 2. Excessive rates: <40/min or >150/min 3. Chest pain 4. Heart failure • If unstable, electrical therapy: cardioversion for tachyarrhythmias, pacing for bradyarrhythmias
- 47. Atropine 0.5 mg each bolus up to 3 mg. Atropine as temporizing measure only. Needs transcutaneous /transvenous pacing
- 48. Four Rhythms At Risk Of Developing Asystole 1. Recent asystole 2. Mobitz II 2nd degree AV Block 3. Complete Heart Block (especially with broad QRS or initial heart rate <40/min) 4. Ventricular standstill more than 3 sec For these, consider also electrical therapy – Only mentioned in European Resuscitation Council Guidelines 2005
- 49. Bradyarrhythmias • 2nd degree Mobitz type 1 • the block is at AV Node • Often transient • Maybe asymptomatic • 2nd degree Mobitz type 2 • Block most often below AV node, at bundle of His or BB • May progress to 3rd degree AV block
- 50. * For polymorphic VT – if patients become unstable, perform defibrillation rather than cardioversion. If ever in doubt whether to perform cardioversion or defibrillation, then perform DEFIBRILLATION Rule of thumb – if your eye cannot synchronize to each QRS complex, neither can the machine!
- 51. Tachyarrhythmias • For stable tachyarrhythmias, we need to further decide whether it is NARROW QRS or WIDE QRS • For each type, further divide into – Regular – Irregular
- 52. Tachyarrhythmias • Narrow QRS tachyarrhythmias – Regular • Sinus Tachycardia, PSVT, atrial flutter with regular AV conduction – Irregular • Atrial Fibrillation, Atrial flutter with variable AV Block • Wide (Broad) QRS tachyarrhythmias – Regular • Ventricular Tachycardia, SVT with BBB – Irregular • Polymorphic VT, AF with BBB
- 53. Narrow complexes and regular – attempt vagal maneuver and adenosine; Narrow complexes but not regular- likely AF. Don’t give adenosine. May attempt rate control using beta blocker or diltiazem
- 54. Amiodarone can be given for both regular and irregular broad complexes
- 55. Recommended Resources • ABC of Clinical Electrocardiography – www.bmj.com • Goldberger: Clinical Electrocardiography: A Simplified Approach, 6th edition. – Access via www.mdconsult.com • ECG Learning Center – http://medstat.med.utah.edu/kw/ecg/index.htm l • ECG Library – http://www.ecglibrary.com/ecghome.html
- 56. Thank You Contact me: Dr. K.S. Chew cksheng74@yahoo.com http://emergencymedic.blogspot.com
Editor's Notes
- Atrial depolarisation Electrically both atria act almost as one. They have relatively little muscle and generate a single, small P wave. P wave amplitude rarely exceeds two and a half small squares (0.25 mV). The duration of the P wave should not exceed three small squares (0.12 s). The wave of depolarisation is directed inferiorly and towards the left, and thus the P wave tends to be upright in leads I and II and inverted in lead aVR. Sinus P waves are usually most prominently seen in leads II and V1. A negative P wave in lead I may be due to incorrect recording of the electrocardiogram (that is, with transposition of the left and right arm electrodes), dextrocardia, or abnormal atrial rhythms. Normal P waves may have a slight notch, particularly in the precordial (chest) leads. Bifid P waves result from slight asynchrony between right and left atrial depolarisation. A pronounced notch with a peaktopeak interval of &gt; 1 mm (0.04 s) is usually pathological, and is seen in association with a left atrial abnormality—for example, in mitral stenosis.
- The R wave in lead V6 is smaller than the R wave in V5, since the V6 electrode is further from the left ventricle. The depth of the S wave, generally, should not exceed 30 mm in a normal individual (although &gt; 30 mm are occasionally recorded in normal young male adults) In another website it is also shown that small q wave seen in leads III and aVF Normal q-waves reflect normal septal activation (beginning on the LV septum); they are narrow (&lt;0.04s duration) and small (&lt;25% the amplitude of the R wave). They are often seen in leads I and aVL when the QRS axis is to the left of +60o, and in leads II, III, aVF when the QRS axis is to the right of +60o. Septal q waves should not be confused with the pathologic Q waves of myocardial infarction (http://medstat.med.utah.edu/kw/ecg/ecg_outline/Lesson3/index.html)
- Sokolow + Lyon (Am Heart J, 1949;37:161) S V1+ R V5 or V6 &gt; 35 mm Cornell criteria (Circulation, 1987;3: 565-72) SV3 + R avl &gt; 28 mm in men SV3 + R avl &gt; 20 mm in women Framingham criteria (Circulation,1990; 81:815-820) R avl &gt; 11mm, R V4-6 &gt; 25mm S V1-3 &gt; 25 mm S V1 or V2 + R V5 or V6 &gt; 35 mm R I + S III &gt; 25 mm Romhilt + Estes (Am Heart J, 1986:75:752-58) Point score system
- ST segment depression is always an abnormal finding, although often nonspecific (http://medstat.med.utah.edu/kw/ecg/ecg_outline/Lesson3/index.html)
- As a general rule, T wave amplitude corresponds with the amplitude of the preceding R wave, though the tallest T waves are seen in leads V3 and V4. Tall T waves may be seen in acute myocardial ischaemia and are a feature of hyperkalaemia.
- Poor Man&apos;s Guide to upper limits of QT: For HR = 70 bpm, QT&lt;0.40 sec; for every 10 bpm increase above 70 subtract 0.02 sec, and for every 10 bpm decrease below 70 add 0.02 sec. For example: QT &lt; 0.38 @ 80 bpm QT &lt; 0.42 @ 60 bpm