Ecg

CVS

1. E C G - Dr. Chintan

2. Normal Impulse Conduction Sinoatrial node AV node Bundle of His Bundle Branches Purkinje fibers

3. Impulse Conduction & the ECG Sinoatrial node AV node Bundle of His Bundle Branches Purkinje fibers

4. The “PQRST” P wave - Atrial depolarization T wave - Ventricular repolarization QRS - Ventricular depolarization

5. The PR Interval Atrial depolarization + delay in AV junction (AV node/Bundle of His) (delay allows time for the atria to contract before the ventricles contract)

6. The ECG Paper Horizontally One small box - 0.04 s One large box - 0.20 s Vertically One small box - 0.1 mV One large box - 0.5 mV

7. An Electrocardiogram

8. Hold It ! SA Node Normal Pacemaker Activation Of The Heart

9. PQ ST P QRS T PR interval QT interval

10. Time 0.04 sec 1 sec 0.2 sec

11. Time Voltage 0.2 seconds 1 milliVolt 0.1 mV

12. Cardiac Cycles

13. 14 HOOKING UP THE 12-LEAD ECG Proper skin prep Placement of the limb electrodes Placement of the chest electrodes

14. ECG Leads A lead can be thought of an eye or pair of eyes watching the heart.

15. Leads: Definitions 16 A lead is a recording electrode or a pair of recording electrodes at a specified location. A lead can also refer to an electrical tracing.

16. Bipolar and Unipolar Leads A bipolar lead has a distinctly positive pole and a distinctly negative pole . These leads include the frontal leads in an ECG: I, II, and III. A unipolar lead has a pole with a distinct positive pole but does not have a distinct negative pole . These leads include aVL, aVR, and aVL . The chest leads are also unipolar: leads V1 through V6.

17. 18 Planes of the Body Some 12-lead ECG leads are on the frontal plane and some are on the horizontal plane . The frontal leads scan the top surface of the body. The horizontal leads sense electrical forces from front to back of the body.

18. Frontal Plane Leads: Lead I Lead I: RA (-) to LA (+) (Right Left, or lateral) Lead I has a positive electrode on the left arm and a negative electrode on the right arm. Lead I is a bipolar, indirect lead. field of observation on the frontal plane of the body.

19. Frontal Plane Leads: Lead II  RA (-) to LF (+) (Superior Inferior) Lead II has a positive electrode on the left foot and a negative electrode on the right arm. Lead II is a bipolar, indirect lead. As a frontal leads, Lead II is a field of sensing on the frontal plane of the body. 20

20. Frontal Plane Leads: Lead III Lead III: LA (-) to LF (+) (Superior Inferior) Lead III has a positive pole on the left foot and a negative pole on the left hand. Lead III is a bipolar, indirect lead. As a frontal leads, Lead III is a field of sensing on the frontal plane of the body. 21

21. Leads I, II, and III: Einthoven’s Triangle These three leads together compose Einthoven’s Triangle . They are bipolar leads . Each lead has a positive and a negative pole. These leads are called indirect because they are more than two cardiac diameters from the heart. Leads I, II, and III are indirect bipolar leads. 22

22. Einthoven's Triangle We can reduce the angles to the area over the chest and form a small triangle. 25

23. Einthoven's Triangle 26 If leads I, II and II are then criss-crossed over the heart , we begin to build a system of leads that will cover the surface of the chest. At this point, we have a triaxial system. Note Leads II and III appear to have traded places. We have room for more coverage in the spaces between I, II, and III.

24. Einthoven’s law Einthoven’s triangle. if we know the voltage of two bipolar leads, the voltage of 3 rd lead can be found by adding the remaining two leads. i.e. II = I + III

25. Augmented Limb Leads: aVL, aVF, and aVL Without adding any more physical leads on the body a number of physicians over time designed the virtual leads aVL, aVF and aVR. These virtual leads use the existing limb leads, I, II, and III, and mathematical formulas to create three additional frontal-plane leads. 28

26. 29 Augmented Limb Leads: aVL, aVF, and aVL aVL, aVF, and aVR are unipolar leads. They use a positive pole on the surface of the body. They use the heart as a negative reference point. The “a’ stands for augmented because the signal is boosted for our vision by the ECG machine. The augmented limb leads are unipolar, indirect, frontal limb leads .

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28. Adding the leads aVL, aVR, and aVF between the open spaces completes the frontal leads of the 12-Lead ECG. We now have six limb leads Now we have an hex axial system. 31 In Summary: Six Limb Leads Frontal Leads.

29. Precordial Leads The three standard limb leads (I, II, and III) and the three virtual leads (aVL, aVF and aVR) compose six of the twelve leads in a 12-lead ECG. The other six leads are the precordial leads. The precordial leads are unipolar leads. They have a positive electrode on the chest wall and use the heart as a general negative reference point. The precordial leads record the heart’s electrical forces in a transverse (or horizontal) plane. The precordial leads are semi-direct l eads because they are close to the heart but not directly on the muscle. 32

30. Precordial (Chest) Leads 33 Chest leads are placed in a circular pattern around the heart: V1: 4 th intercostal space to the immediate right of the sternum . V2: 4 th intercostal space to the immediate left of the sternum. V3: midway between V2 and V4. V4: in the midclavcular line , in the 5 th intercostal space. V5: in the anterior axillary , in the 5 th intercostal space. V6: in the midaxillary line , in the 5 th intercostal space.

31. Precordial Leads 34 Why six anterior leads ? V1 and V2 reflect the right side of the heart V3 and V4 reflect the interventricular septum ( location of His Bundle and Right and Left Bundle Branches V5 and V6 reflect the left side of the heart

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33. Summary of Leads 36 There are six limb leads . They are indirect leads. Three of the limb leads are bipolar: I, II, and III. Three of the limb leads are unipolar: aVL, aVR and aVF. The limb leads are in the frontal plane. There are six precordial (chest) leads . The precordial leads lie in the horizontal plane . They are unipolar, semi-direct leads . Bipolar leads have a negative and positive pole. Unipolar leads have a positive pole and a negative reference in the area of the heart. Indirect leads lie more than the distance of two heart widths from the heart. Semi-direct leads are in close proximity to the heart . Direct leads are in direct contact with the heart.

34. LIMB LEADS Bipolar leads I, II, III Augment leads a VR , a VL , a VF    

35. Chest Leads

36. 39 CHEST LEADS 6 UNIPOLAR LEADS V1 V2 V3 V4 V5 V6

37. CHEST LEADS CHEST LEADS R wave progression Small to Tall

38. Certain conventions to record ECG. For 1mV input there must be 1 cm deflection of stylus. 1 ss on Y-axis = 0.1 mV Speed of the ECG paper is 25 mm/sec. 1 ss on x-axis = 0.04sec . we can double the speed in tachycardia.

39. NORMAL ECG

40. Components of normal ECG Waves of ECG: P-wave QRS complex T-wave U-wave Segments of ECG: PQ or PR segment ST segment Intervals of ECG: PR interval QT interval RR interval

41. P Wave it represents atrial depolarization which occurs just before atrial contraction. The peak of the P wave coincides with time when cardiac impulse reaches the AV node. Amplitude of P wave is 0.1 – 0.2 mV and duration is 0.1 sec

42. QRS Complex Due to ventricular depolarization which occurs just before ventricular contraction. Voltage is variable in different leads. We take the voltage from the peak of R wave to the bottom of S wave. Duration : 0.08 to 0.1 sec Q wave is due to depolarization of upper part of ventricular septum , R wave is due to depolarization of lower part of septum and apex of heart. S wave is due to depolarization of wall and base of the ventricle . The peak of the R wave coincides with the beginning of the ventricular systole.

43. Vent. DEPOLARIZATION Vent. REPOLARIZATION

44. T Wave a positive wave, due to ventricular repolarization Voltage = 0.2 – 0.3 mV Duration = 0.16 - 0.20 sec. End of the T wave approximately coincides with the end of ventricular systole.

45. U WAVE Sometimes there is U wave after T wave which is due to slow repolarization of papillary muscle U wave becomes prominent in hypokalemia. Note : Wave of atrial repolarization is masked by QRS complex.

46. SEGMENTS OF ECG PR OR PQ segment: End of P wave to beginning of Q wave. 0.05-0.12 sec ST Segment: End of S WAVE to beginning of T wave. 0.08-0.12 sec These two segments are isoelectric because there is no current flow in heart. In PR segment , atria are completely depolarized. In ST segment ventricles are completely depolarized. CLINICAL : In acute myocardial infarction (MI) there is elevation of ST segment due to flow of injury current which flows between the area of infarction and normal myocardium.

47. INTERVALS OF ECG

48. PR Interval between beginning of P wave and beginning of QRS complex. It represents the atrial depolarization plus conduction through AV node. AV conduction is also included in PR interval. Duration : On average it is 0.16 sec. range is 0.12 to 0.2 sec. It is prolonged in rheumatic fever and different types of AV blocks and also in hypokalemia. PR interval is shortened in accelerated AV conductions and in WPW syndrome . It is approximately equal to interval between the beginning of atrial contraction and beginning of ventricular contraction.

49. QRS Interval duration of QRS complex: 0.08 to 0.12 sec. Prolonged in bundle branch blocks and ventricular extra systoles.

50. QT Interval From beginning of Q wave to end of T wave. It represents ventricular depolarization and ventricular repolarization duration = 0.36 to 0.4 sec. it is approximately equal to the duration of ventricular systole. Shortened in Hypercalcemia. Prolonged in hypocalcaemia and also in ventricular extra systole.

51. RR INTERVAL interval between two successive R waves. It is equal to duration of one cardiac cycle i.e. 0.8 sec.

52. Calculation of heart rate from ECG If the heart rate is regular then by RR interval, we can find out the heart rate by the following formulae: 60 / RR interval or 300 / no. of large squares b/w two successive R waves. or 1500 / no. of smallest squares between two successive R waves. In case of irregular heart rate we can’t use this formula. In that case we count the number of heart beats in 6 seconds and multiply it with ten.

53. Table 28-2. ECG intervals.   Normal Duration(s) Events in the Heart Intervals Average Range During Interval PR interval 1 0.18 2 0.12-0.20 Atrial depolarization and conduction through AV node QRS duration 0.08 to 0.10 Ventricular depolarization and atrial repolarization QT interval 0.40 to 0.43 Ventricular depolarization plus Ventricular repolarization ST interval (QT minus QRS ) 0.32 . . . Ventricular repolarization 1 Measured from the beginning of the P wave to the beginning of the QRS complex. 2 Shortens as heart rate increases from average of 0.18 at a rate of 70 beats/min to 0.14 at a rate of 130 beats/min.

54. Determination Of QRS axis

55. 60 EINTHOVENS TRIANGLE

56. QRS Axis Determination

57. Axis in Normal range

58. Left Axis Deviation

59. Right Axis Deviation

60. Atrial premature beat (lead I).

61. Premature ventricular contractions (PVCs)

62. ECG CHANGES in MI ST elevation => Convexity upwards and elevated segment merged with T wave. T wave inversion => Pathological Q wave => Wider and deeper. Depth more than one third the height of R wave of that QRS complex.

63. SYSTEMATIC INFARCT RECOGNITION Infarct location: ST Elevation Found In: Anterior – Septal :- V1, V2, V3 and V4 Posterior :- V1 and V2 Inferior :- II, III and aVF High Lateral :- I and aVL Low Lateral :- V5 and V6

64. HYPERKALEMIA (K + > 5 meq / L) Increase in potassium in ECF Prolonged Depolarisation Initially tall T wave Later wide QRS complex, Diminished or absent P wave, reduced QT interval. arrhythmia and ultimately asystole .

65. HYPOKALEMIA (K + < 3.5 meq / L) Decrease in potassium ion in ECF Delayed ventricular repolarization (1) prolonged PR interval (2) ST segment depression (3) T wave inversion (4) U wave present (5) Reduced amplitude of QRS complex

66. HYPERCALCAEMIA Increase calcium in ECF Increased myocardial contractility Heart relaxes less during diastole Short ST segment & short QT interval Eventually stops in systole CALCIUM RIGOR

67. HYPOCALCAEMIA Reduced calcium in ECF Reduced myocardial contractility Prolongation of ST segment Prolongation of QT interval

68. ThanQ ………………