The document discusses electrocardiography (ECG), providing details on the standard 12-lead ECG procedure, what each lead measures, and ECG paper formatting. Common cardiac arrhythmias and conduction abnormalities that can be detected from the ECG are summarized, including sinus bradycardia, atrial flutter, atrial fibrillation, ventricular tachycardia, and Wolff-Parkinson-White syndrome. Characteristics of right and left bundle branch block are also outlined.

1. EKG 12 LeadsInternal Medicine2010

2. ElectrocardiographyA recording of the electrical activity of the heart over timeGold standard for diagnosis of cardiac arrhythmiasHelps detect electrolyte disturbancesAllows for detection of conduction abnormalitiesScreening tool for ischemic heart disease (stress tests)Helpful with non-cardiac diseases

3. ECG LeadsThe standard EKG has 12 leads:3 Standard Limb Leads3 Augmented Limb Leads6 Precordial Leads

4. ECG Limb LeadsLeads are electrodes which measure the difference in electrical potential between either: 1. Two different points on the body (bipolar leads) 2. One point on the body and a virtual reference point with zero electrical potential, located in the center of the heart (unipolar leads)

5. Recording of the ECGLimb leads are I, II, II. Each of the leads are bipolar; i.e., it requires two sensors on the skin to make a lead.If one connects a line between two sensors, one has a vector.There will be a positive end at one electrode and negative at the other.The positioning for leads I, II, and III were first given by Einthoven (Einthoven’s triangle).

6. ECG Limb Leads

7. Precordial Leads

8. Summary of Leads

9. Arrangement of Leads on the EKG

10. Anatomic Groups

11. Anatomic Groups

12. Anatomic Groups

13. Anatomic Groups

14. Anatomic Groups

15. ECG Graph PaperRuns at a paper speed of 25 mm/secEach small block of ECG paper is 1 mm2At a paper speed of 25 mm/s, one small block equals 0.04 sFive small blocks make up 1 large block which translates into 0.20 s5 large blocks per secondVoltage: 1 mm = 0.1 mV between each individual block vertically

16. The Normal Conduction System

18. ECG Tracing

19. Guide in ECG ReadingRhythmRate: Atrial and VentricularAxisP wave: morphology and durationP – R intervalQRS complex: morphology and durationST segmentT waveU waveQ – T interval

20. Determining the RhythmRegular or IrregularAccessing whether the PP intervals and RR intervals are regularly spacedIf the rhythm is irregular, determine if:Occasionally irregularRegularly irregular (there is the pattern of irregularity)Irregularly irregular (no pattern of irregularity)

21. Determining the Heart RateRule of 300Take the number of “big boxes” between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the rateAlthough fast, this method only works for regular rhythms.10 Second RuleAs most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds.This method works well for irregular rhythms.

22. The QRS AxisThe QRS axis represents the net overall direction of the heart’s electrical activity.By near-consensus, the normal QRS axis is defined as ranging from -30° to +90°.-30° to -90° is referred to as a left axis deviation (LAD)+90° to +180° is referred to as a right axis deviation (RAD)

23. The QRS Axis

24. The QRS Axis The Quadrant Approach1. Examine the QRS complex in leads I and aVF to determine if they are predominantly positive or predominantly negative. The combination should place the axis into one of the 4 quadrants below.

25. The QRS Axis The Quadrant Approach2. In the event that LAD is present, examine lead II to determine if this deviation is pathologic. If the QRS in II is predominantly positive, the LAD is non-pathologic (in other words, the axis is normal). If it is predominantly negative, it is pathologic.

26. P-waveDepolarization of both atriaRelationship between P and QRS helps distinguish various cardiac arrhythmiasShape and duration of P may indicate atrialenlargement

27. ECG Tracing

28. P wave morphologyIAVRUpright PInverted PV1Biphasic P4

29. PR intervalfrom onset of P wave to onset of QRSNormal duration = 0.12-2.0 sec (120-200 ms) (3-4 horizontal boxes)Represents atria to ventricular conduction time (through His bundle)Prolonged PR interval may indicate a 1st degree heart block

30. ECG Tracing

31. P – R intervalNormal = 0.12 – 0.22Short = < 0.12Prolonged = > 0.22

32. QRS complexVentricular depolarizationLarger than P wave because of greater muscle mass of ventriclesNormal duration = 0.08-0.12 seconds

33. ECG Tracing

34. QRS complexIts duration, amplitude, and morphology are useful in diagnosing cardiac arrhythmias, ventricular hypertrophy, MI, electrolyte derangement, etc.Q wave greater than 1/3 the height of the R wave, greater than 0.04 sec are abnormal and may represent MI

35. QRS morphology and durationIAVRPositive QRSNegative QRSV3Biphasic QRS6

36. ST segmentConnects the QRS complex and T waveDuration of 0.08-0.12 sec (80-120 msec)

37. ECG Tracing

38. S – T SegmentIV1Normal ElevatedV3Depressed7

39. T wavesRepresents repolarization or recovery of ventriclesInterval from beginning of QRS to apex of T is referred to as the absolute refractory period

40. ECG Tracing

41. T wave morphologyAVRIUpright TInverted T8

42. QT IntervalMeasured from beginning of QRS to the end of the T waveNormal QT is usually about 0.40 secQT interval varies based on heart rate

43. ECG Tracing

45. Chamber EnlargementRight Atrial Enlargement (RAE)Tall P waves in II, III, AVF > 2.5mmLeft Atrial Enlargement (LAE)P wave in I > 0.11 secsTerminal Negativity of P wave in VI = > 1mmBi-atrial EnlargementRAE + LAE

46. Sinus BradycardiaHeart is slower than 60 beats per minuteRR interval is longerP wave followed by QRS complex in 1:1 ratioPR interval slightly prolonged

47. Sinus TachycardiaSinus rhythm is faster than 100 beats per minuteRR interval is shorter, less than 0.6 secondsP wave followed by QRS complex in 1:1 ratio

48. Atrial Flutteratria contract at 200-350 beats per minute F waves are larger than normal P waves and they have a saw-toothed waveformventricular rate is usually regular but slower than the atrial ratefixed ratio of flutter waves to QRS complexes can be observed, for instance 2:1, 3:1 or 4:1

49. Atrial Flutter

50. Atrial Fibrillationoccurs when the atria depolarize repeatedly and in an irregular uncontrolled manner usually at atatrial rate greater than 350 beats per minuteno concerted contraction of the atriaNo P-waves are observed QRS complexes have normal shape, due to normal ventricular conduction. However the RR intervals vary from beat to beat. The ventricular rate may increase to greater than 150 beats per minute if uncontrolled.

51. Atrial Fibrillation

52. Ventricular Tachycardiaoccurs when electrical impulses originating either from the ventricles cause rapid ventricular depolarization (140-250 beats per minute)QRS complexes are wide and bizarreP-waves may be inverted/may be present but not associated with QRS complexes (AV dissociation)RR intervals are usually regular

53. Ventricular Tachycardia

54. Ventricular Fibrillationoccurs when parts of the ventricles depolarize repeatedly in an erratic, uncoordinated mannerrandom, apparently unrelated wavesno recognizable QRS complexalmost invariably fatal because the uncoordinated contractions of ventricular myocardiumelectrical defibrillation restores normal regular rhythm

55. Ventricular Fibrillation

56. Wolff-Parkinson-White Syndromepresence of an accessory atrioventicular pathway located between the wall of the right or left atria and the ventricles, known as the Bundle of Kent - allows the impulse to bypass the AV node and activate the ventricles prematurelyinitial slur to the QRS complex, known as a delta wave may be observedQRS complexes are wide, > 0.11 secPR is shortened, to less than 0.12 sec

57. Wolff-Parkinson-White Syndrome

58. Right Bundle Branch BlockCriteria for right bundle branch block (RBBB) [1] QRS >0,12 sec Slurred S wave in lead I and V6 RSR'-pattern in V1 where R' > R

59. Left Bundle Branch BlockQRS duration is 120 msec or greaterpoor R wave progression in V 1 thru V4T wave vector is in the opposite direction to the QRS vector (T waves are inverted in I, V5 and V6)conduction abnormality often appears as "rabbit ears" (rsR pattern) on the left side of the chest (V4,5,6)