Principles of electrocardiography ppt

ecg,veterinary ecg, small animal elecrocardiogram

1. Principles of Electrocardiography   Submitted to : Dr. V. K. Gupta, Senior Scientist Division of Veterinary Medicine, IVRI, Izatnagar Submitted by: Suthar Abhinav , Roll no M 5388, Division of veterinary Medicine, IVRI, Izatnagar

2. Principles of Electrocardiography   What is an ECG?? Electrocardiogram = EKG = ECG A recording of the electrical activity of the heart from electrodes placed on the surface of skin.

3. Electrocardiograph Electrocardiograph (ECG machine) is a voltmeter (or galvanometer ) that records the changing electrical activity of the heart between a positive and negative electrode. Electrocardiography is the process of recording this electrical changes.

4. Indications

5. Indications for an electrocardiogram: Cardiac arrhythmias. Acute onset of dyspnoea Shock. Fainting or seizures. Cardiac monitoring during and after surgery. Cardiac murmurs. Cardiomegaly found on thoracic radiographs.

6. Cyanosis. Pre operatively in older animals. Evaluating the effect of cardiac drugs – especially digitalis, quinidine and propanolol . Electrolyte disturbances, especially potassium abnormalities. Systemic diseases that affect the heart. Serial electrocardiograms as an aid in the prognosis and diagnosis of cardiac disease.

7. Normal Conduction System

8. The 1st Rule of ECG A current of depolarization traveling towards the + electrode is recorded as a positive deflection A current of depolarization traveling away from the + electrode is seen as a negative deflection A current of repolarization traveling away from the + electrode is seen as a positive deflection

9. Positive and Negative Deflection in a lead A wave of electrical depolarization moves towards the positive pole of the lead – a + ve deflection occurs

10. LIMITATIONS ECG must always be evaluated in conjunction with clinical findings An animal with CHF may have a normal ECG and normal animal may show non specific electrocardiographic abnormalities

11. Types of ECG

12. Single channel recorder Has one stylus – records one lead at a time Multiple channel recorder Has more than one stylus Provide simultaneous tracings of 3 leads

13. Position & Restraint Lateral recumbency - the standard position for canine and feline electrocardiography No chemical restraint Trained attendant or animal owner Lead placement

14. Electrodes & Leads

15. ELECTRODES Alligator clips or flat contact electrodes Hair and stern surrounding the electrode should be moistened with conductive gel or alcohol Standard paper speed : 50 mm/sec. Left Arm (LA), Right Arm (RA) and Left Leg (LL)

16. BIPOLAR STANDARD LEADS Lead I : Right arm (-) compared with Left (+) arm Lead II : Right arm (-) compared with Left (+) leg Lead III : Left arm (-) compared with Left (+) leg AUGMENTED UNIPOLAR LIMB LEADS aVR :Augmented Vector Right aVL : Augmented Vector Left aVF : Augmented Vector Front SPECIAL LEADS Lead CV 5 RL (V 2 ) Lead CV 6 LL (V 2 ) Lead CV 6 LU (V4) Lead V 10 LEAD SYSTEM

17. STANDARD LEADS Useful for studying 1. Abnormalities in the P-QRS-T deflection 2. Diagnosing cardiac arrhythmias 3. Determining the mean electrical axis

18. L I, II, III, aVR , aVL , & aVF - Frontal plane leads. L V1, V2, V3, V4, V5, V6, & V10 – Horizontal (or transverse) plane leads.

19. NORMAL ECG P : Atrial depolarisation QRS : Ventricular depolarisation T : Ventricular repolarisation

20. QRS Complex T wave

21. Normal ECG Parameters - Dog & Cat Heart Rate (beats per minute) : Canine : Adults: 70-160 Toy Breeds: up to 180 Puppies: up to 220 Feline : 160-240

22. Amplitudes (mV) in lead II Canine Feline P amp < 0.4 < 0.2 R < 20 kg: < 2.5 0.9 > 20 kg: < 3.0 <

23. Intervals (seconds) Canine Feline P < 0.04 < 0.04 PR 0.06 -0.13 0.05 - 0.09 QRS < 20 kg: < 0.05 < 0.04 > 20 kg: < 0.06 QT 0.15 to 0.25 0.12 to 0.18

24. Normal ECG Parameters - Dog & Cat Rhythm Canine : Normal sinus rhythm Sinus arrhythmia Wandering atrial pacemaker Feline : Normal sinus rhythm Sinus tachycardia

25. Methodical approaches to ECG

26. ECG interpretation essentially involves four main steps: Calculation of the heart rate; Determination of the heart rhythm; Measurement of the complex amplitudes and intervals; MEASUREMENT OF THE MEAN ELECTRICAL AXIS: A good understanding of the electrical activity of the heart is key to the accurate interpretations of ECG (Martin, 2002).

27. How to measure heart rate ???

28. See the Rhythm …Regular or irregular???

29. Rhythm Regular irregular Irregular irregular

30. How to decide MEA???

31. There are three common methods of calculating the MEA in the frontal plane. The Vector Method:  Using leads I, II or III and the frontal plane diagram, calculate the algebraic sum of the QRS deflections in any two leads. The Isoelectric Method. The Largest Net Deflection Method.

32. Normal ECG

33. PQRST Wave System

34. P wave

35. P wave Width: maximum, 0.04 sec (2 boxes wide)maximum, 0.05 sec (2 ½ boxes wide) in giant breeds. Height: maximum, 0.4 mV (4 boxes tall).

36. Left atrial enlargement - P too wide in L II. Dog & Cat : P > 0.04 sec Right atrial enlargement - P too high in L II. Dog: P > 0.4 mv ; Cat: P > 0.2 mv Biatrial enlargement - P too tall and wide in L II.

37. Rt Atrial enlargement (P Amp )

38. QRS wave

39. QRS complex Width: maximum, 0.05 sec (2 ½ boxes wide) in small breeds. maximum, 0.06 sec (3 boxes) in large breeds. Height of R wave*: maximum, 3.0 mV (30 boxes) in large breeds. maximum, 2.5 mV (25 boxes) in small breeds. P-R interval Width: 0.06 to 0.13 sec (3 to 6 ½ boxes).

40. Wide QRS Complexes Etiologies: Aberrant conduction (Bundle Branch Block) Myocardial hypoxemia/ischemia Left ventricular enlargement

41. Low amplitude QRS complexes Etiologies: Pleural effusion ,Pericardial effusion, Obesity ,Hypothyroidism, Pneumothorax and Diffuse myocardial disease.

42. Left Ventricular Enlargement R wave amplitude in L II increased. QRS duration in L II increased.

43. Lt Ventricular Enlargement (Increased R Amp)

44. Rt. Ventricular enlargement Presence of an S wave in leads I, II, III. MEA in the frontal plane shifted to the right (pointing to the right ventricle): 100° to – 75° Deep S wave in lead V3; S = 0.7 mv Deep Q waves in leads I,II and III and after aVF greater than 9.5 mV (5 boxes)

45. Rt. Ventricular enlargement

46. T wave

47. T wave Can be positive, negative or diphasic Not greater than one fourth amplitude of R wave ; amplitude range + 0.05 – 1.0 mV (1/2 to 10 boxes) in any lead.

48. T wave abnormalities Should not be greater than 1/4 of the R wave. Sharply pointed (or) Notched – Electrolyte imbalances E lectolyte abnormality

49. Peaked T wave

50. Q-T interval duration Dog : 0.15 to 0.25 sec (7 ½ to 12 ½ boxes) Cat : 0.12 to 0.18 sec Faster the heart rate, shorter the Q-T interval Q-T interval should be less than half the preceding R-R interval

51. Prolongation of Q-T interval Myocardial problems, Toxicity or Hypoxia, Hypokalemia Hyperkalemia Hypocalcemia Antiarrhythmic drugs Shortening of QT interval Hypercalcemia

52. ST segment abnormalities ST segment depression - 0.2 mV ;seen in Myocardial ischemia Myocardial infarction Hyper and Hypokalemia Trauma to the heart. ST segment elevation - 0.15 mV in Lead I ; seen in Pericarditis , Severe ischaemia /infarction (e.g. full wall thickness).

53. Sinus Arrhythmia and Wandering Atrial Pacemaker in the Dog Sinus arrhythmia - Irregular ventricular rhythm which is of sino-atrial origin.  On the EKG, the QRS to QRS interval varies and there is a P wave for every QRS complex.

54. Sinus Arrhythmia

55. Wandering Atrial Pacemaker in the Dog

56. Sinus rhythm: A sequence of beats originating from the sino atrial node forms a rhythm, known as the sinus rhythm. there are four common sinus rhythms.

57. Sinus Bradycardia in the Dog Hypothyroidism , 2. Hypothermia, 3. Hyperkalemia , 4. Hypoglycemia 5. Enhanced parasympathetic tone as with: Increased inspiratory effort, Gastric irritation, Increased CSF pressure. Atropine will abolish the bradycardia (atropine - 0.04 mg/kg IV)

58. Sinus bradycardia In Sinus bradycardia , the SA Node generates an impulse and depolarization occurs more slowly than normal. This can be a normal feature in some giant breed dogs and in athletically fit animals. The ECG shows a normal sinus rhythm but at a slower rate than normal.

59. Sinus bradycardia

60. Sinus tachycardia In Sinus tachycardia , the SA Node generates an impulse and depolarization occurs faster than normal. The ECG shows a normal sinus rhythm but at a faster rate than normal.

61. Sinus Tachycardia It is a sinus rhythm with an increased ventricular rate. Dog (<20 kg) with heart rate 180 bpm Dog (20 kg) with heart rate 160 bpm Puppies with heart rate 220 bpm Cat with heart rate 240 bpm Etiology: Pain,Fever , Anemia, Reduced cardiac output, Hyperthyroidism & Excitement.

62. Atrial fibrillation Irregular rhythm and absence of P waves

63. Absence of P Wave ( Atrial Fibrillation)

64. Ventricular premature contractions (VPC) Premature beats. QRS complexes are wide & bizarre. Common finding in dogs and cats and arise from an ectopic focus or foci within the ventricular myocardium.

65. Ventricular Tachycardia (VT) Refers to runs of greater than 3 PVC's in sequence. Markedly reduce cardiac output ( dysynergy of contraction). Etiology is as for PVC.

66. Other abnormalities Right bundle branch block Wide S waves QRS complex greater than 0.08 sec. Left bundle branch block QRS complex greater than 0.08 sec duration QRS complex wide and + ve .

67. Artifacts Muscle tremor artifact. Movement artifact. Electrical interference. Electrical alternans Alternation in the size of the QRS amplitude that occurs nearly every other beat.

68. Artifact

69. Thank U Comments, corrections or additions are welcome.