ECG An Introduction
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The document provides an overview of electrocardiography (ECG). It discusses the history of ECG development. It then covers how to perform an ECG, how an ECG works by detecting electrical changes during heartbeats, ECG paper calibration, the 12 leads, and how to interpret various ECG components like rate, rhythm, axes, waves, intervals, and segments. Key points about normal ECG readings are also presented along with 10 interpretation rules.
ECG An Introduction
- 2. Presented by: فیصل محمد معاونین:نزیر،وسیم ،جنید اختر دانشاحمد P.G Scholars DEPARTMENT OF ILMUL JARAHAT NATIONAL INSTITUTE OF UNANI MEDICINE, KOTTIGEPALYA, MAGADI MAIN ROAD. BANGALORE-91.
- 3. 1. History 2. What is an ECG? 3. HOW TO DO ELECTROCARDIOGRAPHY 4. How does an ECG work? 5. ECG Paper 6. Calibration of ECG 7. LEADS 8. Rate 9. Rhythm 10.Cardiac Axis 11.P – wave 12.PR - interval 13.QRS Complex 14.ST Segment 15.QT interval (Include T and U wave)
- 4. • 1842- Italian scientist Carlo Matteucci realizes that electricity is associated with the heart beat • 1876- Irish scientist Marey analyzes the electric pattern of frog’s heart • 1895 - William Einthoven , credited for the invention of EKG • 1906 - using the string electrometer EKG, William Einthoven diagnoses some heart problems
- 5. • 1924 - the noble prize for physiology or medicine is given to William Einthoven for his work on EKG • 1938 -AHA and Cardiac society of great Britan defined and position of chest leads • 1942- Goldberger increased Wilson’s Unipolar lead voltage by 50% and made Augmented leads • 2005- successful reduction in time of onset of chest pain and PTCA by wireless transmission of ECG on his PDA.
- 8. It can provide evidence to support a diagnosis, but remember….. LOOK AT THE PATIENT NOT JUST THE PAPER
- 9. •The electrocardiogram (ECG) is a representation of the electrical events of the cardiac cycle. •Each event has a distinctive waveform •the study of waveform can lead to greater insight into a patient’s cardiac pathophysiology.
- 10. •Chamber hypertrophy •Arrhythmias •IHD •Pericarditis •Electrolyte disturbances (i.e. hyperkalemia, hypokalemia) •Drug toxicity (i.e. digoxin and drugs which prolong the QT interval)
- 11. 1. Place the patient in a position. If the patient cannot tolerate being flat, you can do the ECG in a more upright position. 2. Instruct the patient to place their arms down by their side and to relax their shoulders. 3. Make sure the patient's legs are uncrossed. 4. Remove any electrical devices, such as cell phones, away from the patient as they may interfere with the machine. 5. If you're getting artifact in the limb leads, try having the patient sit on top of their hands. 6. Causes of artifact: patient movement, loose/defective electrodes/apparatus, improper grounding. HOW TO DO ELECTROCARDIOGRAPHY An ECG with artifacts. Patient, supine position
- 12. The ECG works mostly by detecting and amplifying the tiny electrical changes on the skin that are caused when the heart muscle "depolarizes" during each heart beat. Simply Electrical stimulation through the atria and ventricles-- ----depolarization Return to resting state after stimulation (depolarization) is called repolarization.
- 14. ▪ P wave—atrial depolarization (stimulation) ▪ QRS complex—ventricular depolarization (stimulation) ▪ ST segment, T wave, and U wave—ventricular repolarization (recovery)
- 15. • Horizontally – One small box - 0.04 s – One large box - 0.20 s • Vertically – One large box - 0.5 Mv – One page of ECG - 10 sec
- 16. The electrocardiograph must be properly calibrated so that a 1-mV signal produces a 10-mm deflection. ECG paper (25 mm/sec, 10 mm/mV). A, Electrocardiograph set at normal standardization. B, One half standardization. C, Two times normal standardization.
- 17. ECG illustrating the 12 leads. The leads can be subdivided into two groups: The six limb(extremity) leads And the six chest (precordial) leads The six limb leads—I, II, III, aVR, aVL, and They can be further divided into two subgroups Three standard “bipolar” limb leads (I, II, and III), and three augmented “unipolar” limb leads (aVR, aVL, and aVF).
- 18. Lead I, for example, records the difference in voltage between the left arm (LA) and right arm (RA) electrodes: Lead I = LA – RA Lead II records the difference between the left leg (LL) and right arm (RA) electrodes: Lead II = LL – RA Lead III records the difference between the left leg (LL) and left arm (LA) electrodes: Lead III = LL – LA
- 19. Einthoven's triangle Lead I + Lead III = Lead II I =LA-RA III=LL-LA I+III=LL-RA=II Einthoven’s equation
- 20. A, Einthoven's triangle. B, The triangle is converted to a triaxial diagram by shifting leads I, II, and III so that they intersect at a common point.
- 21. Nine leads have been added to the original three “bipolar” extremity leads. In the 1930s, Dr. Frank N. Wilson and his colleagues at the University of Michigan invented the “unipolar” limb leads and also introduced the six “unipolar” chest leads, V1 through V6. A short time later, Dr. Emanuel Goldberger invented the three augmented unipolar limb leads: aVR, aVL, and aVF. The abbreviation a refers to augmented; V tovoltage; R, L, and F to right arm, left arm, and left foot (leg), respectively. Today 12 leads are routinely employed, consisting of the six limb leads (I, II, III, aVR, aVL, and aVF) and the six precordial leads (V1 to V6).
- 22. aVR + aVL + aVF = 0
- 30. ECGINTERPRETATION The More You See, The More You Know
- 31. Rate Rhythm Cardiac Axis P – wave PR - interval QRS Complex ST Segment QT interval (Include T and U wave) Other ECG signs
- 32. 300 the number of BIG SQUARE between R-R interval Rate = As a general interpretation, look at lead II at the bottom part of the ECG strip. This lead is the rhythm strip which shows the rhythm for the whole time the ECG is recorded. Look at the number of square between one R-R interval. To calculate rate, use any of the following formulas: 1500 the number of SMALL SQUARE between R-R interval OR Rate =
- 33. 300 Rate = For example: 3 1500 15 Rate =or Rate = 100 beats per minute
- 34. If you think that the rhythm is not regular, count the number of electrical beats in a 6- second strip and multiply that number by 10.(Note that some ECG strips have 3 seconds and 6 seconds marks) Example below: 1 2 3 4 5 6 7 8 = (Number of waves in 6-second strips) x 10 = 8 x 10 = 80 bpm Rate There are 8 waves in this 6-seconds strip.
- 35. You can also count the number of beats on any one row over the ten-second strip (the whole lenght) and multiply by 6. Example: = (Number of waves in 10-second strips) x 6 = 13 x 6 = 78 bpm Rate
- 36. Look at p waves and their relationship to QRS complexes. Lead II is commonly used Regular or irregular? If in doubt, use a paper strip to map out consecutive beats and see whether the rate is the same further along the ECG. Measure ventricular rhythm by measuring the R-R interval and atrial rhythm by measuring P-P interval.
- 37. ECG rhythm characterized by a usual rate of anywhere between 60-99 bpm, every P wave must be followed by a QRS and every QRS is preceded by P wave. Normal duration of PR interval is 3-5 small squares. The P wave is upright in leads I and II Normal Sinus Rhythm
- 38. Sinus Bradycardia RHYTHM Rate < 60bpm, otherwise normal
- 39. RHYTHM Sinus Tachycardia Rate >100bpm, otherwise, normal
- 40. RHYTHM Atrial Fibrillation A-fib is the most common cardiac arrhythmia involving atria. Rate= ~150bpm, irregularly irregular, baseline irregularity, no visible p waves, QRS occur irregularly with its length usually < 0.12s
- 41. RHYTHM Ventricular Fibrillation A severely abnormal heart rhythm (arrhythmia) that can be life-threatening. Emergency- requires Basic Life Support Rate cannot be discerned, rhythm unorganized
- 42. RHYTHM Ventricular tachycardia fast heart rhythm, that originates in one of the ventricles- potentially life-threatening arrhythmia because it may lead to ventricular fibrillation, asystole, and sudden death. Rate=100-250bpm
- 43. CARDIAC AXIS Electrical impulse that travels towards the electrode produces an upright (positive) deflection (of the QRS complex) relative to the isoelectric baseline. One that travels away produces negative deflection. And one that travels at a right angle to the lead, produces a biphasic wave. The cardiac axis refers to the general direction of the heart's depolarization wavefront (or mean electrical vector) in the frontal plane. With a healthy conducting system the cardiac axis is related to where the major muscle bulk of the heart lies.
- 44. The normal QRS axis should be between - 30 and +90 degrees. Left axis deviation is defined as the major QRS vector falling between -30 and -90 degrees. Right axis deviation occurs with the QRS axis is between +90 and +180 degrees. Indeterminate axis is between +/- 180 and -90 degrees.
- 45. CARDIAC AXIS Axis Lead I Lead II Lead III Normal Positive Positive Positive/Negative Right axis deviation Negative Positive Positive Left axis deviation Positive Negative Negative To determine cardiac axis look at QRS complexes of lead , II, III. Remember, positive(upgoing) QRS omplex means the impulse travels towards the lead. Negative means moving away.
- 49. Cardiac Axis Causes Left axis deviation Normal variation in pregnancy, obesity; Ascites, abdominal distention, tumour; left anterior hemiblock, left ventricular hypertrophy, Inferior MI Right axis deviation normal finding in children and tall thin adults, chronic lung disease(COPD), left posterior hemiblock, anterolateral MI. North West emphysema, hyperkalaemia. lead transposition, artificial cardiac pacing, ventricular tachycardia CARDIAC AXIS
- 50. Normal P- wave 3 small square wide, and 2.5 small square high. Always positive in lead I and II in NSR Always negative in lead aVR in NSR Commonly biphasic in lead V1 P -WAVE
- 51. P -WAVE P pulmonale Tall peaked P wave. Generally due to enlarged right atrium- commonly associated with congenital heart disease, tricuspid valve disease, pulmonary hypertension and diffuse lung disease. Biphasic P wave Its terminal negative deflection more than 40 ms wide and more than 1 mm deep is an ECG sign of left atrial enlargement. P mitrale Wide P wave, often bifid, may be due to mitral stenosis or left atrial enlargement.
- 52. PR INTERVAL NORMAL PR INTERVAL PR-Interval 3-5 small square (120-200ms) (start of P to start of Q)
- 53. PR-INTERVAL First degree heart block P wave precedes QRS complex but P-R intervals prolong (>5 small squares) and remain constant from beat to beat
- 54. Second degree heart block 1. Mobitz Type I or Wenckenbach Runs in cycle, first P-R interval is often normal. With successive beat, P-R interval lengthens until there will be a P wave with no following QRS complex. The block is at AV node, often transient, maybe asymptomatic PR-INTERVAL
- 55. Second degree heart block 2. Mobitz Type 2 P-R interval is constant, duration is normal/prolonged. Periodically, no conduction between atria and ventricles- producing a p wave with no associated QRS complex. (blocked p wave). The block is most often below AV node, at bundle of His or BB, May progress to third degree heart block PR-INTERVAL
- 56. Third degree heart block (Complete heart block) No relationship between P waves and QRS complexes An accessory pacemaker in the lower chambers will typically activate the ventricles- escape rhythm. Atrial rate= 60-100bpm. Ventricular rate based on site of escape pacemaker. Atrial and ventricular rhythm both are regular. PR-INTERVAL
- 57. QRS complex< 3 small square (0.06 - 0.10 sec) QRS COMPLEX
- 58. Normal duration- 0.06 - 0.10 sec (upto 3 small squares) Depth of the S wave must not exceed 30 mm. Nonpathological Q waves may present in I, III, aVL, V5, and V6.
- 59. The R wave must grow from V1 to at least V4 The S wave must grow from V1 to at least V3 and disappear in V6
- 60. • ST Segment is flat (isoelectric) • Elevation or depression of ST segment by 1 mm or more is abnormal. • “J” (Junction) point is the point between QRS and ST segment • S in V1 or V2 + R in V5 or V6 should be less than 35 mm. • V1 R/S ratio or V6 S/R ratio should be less than1mm.
- 61. • Normal T wave is asymmetrical, first half having a gradual slope than the second • Should be at least 1/8 but less than 2/3 of the amplitude of the R • T wave amplitude rarely exceeds 10 mm. • Abnormal T waves are symmetrical, tall, peaked, biphasic or inverted.
- 63. 1. Total duration of Depolarization and Repolarization. 2. QT interval decreases when heart rate increases. 3. For HR = 70 bpm, QT<0.40 sec. 4. QT interval should be 0.35 0.45 s, 5. Should not be more than half of the interval between adjacent R waves (RR interval).
- 65. • U wave related to depolarizations which follow repolarization. • U waves are small, round, symmetrical and positive in lead II, with amplitude < 2 mm • U wave direction is the same as T wave • More prominent at slow heart rates
- 66. RULE 1 PR interval should be 120 to 200 milliseconds or 3 to 5 little squares
- 67. RULE 2 The width of the QRS complex should not exceed 110 ms, less than 3 little squares
- 68. RULE 3 The QRS complex should be dominantly upright in leads I and II
- 69. RULE 4 QRS and T waves tend to have the same general direction in the limb leads
- 70. RULE 5 All waves are negative in lead aVR
- 71. RULE 6 The R wave must grow from V1 to at least V4 The S wave must grow from V1 to at least V3 and disappear in V6
- 72. RULE 7 The ST segment should start isoelectric except in V1 and V2 where it may be elevated
- 73. RULE 8 The P waves should be upright in I, II, and V2 to V6.
- 74. RULE 9 There should be no Q wave or only a small q less than 0.04 seconds in width in I, II, V2 to V6
- 75. RULE 10 The T wave must be upright in I, II, V2 to V6