CLINICAL ECG

1
WELCOME
2
CLINICAL ECG

• Presented by
• Hemanth Das,
• I MD Organon.

3

• ECG stands for electrocardiogram, or
  electrocardiograph. In some countries, the
  abbreviation used is EKG. Electrocardiograph is
  a sophisticated galvanometer, a sensitive
  electromagnet, which can detect record changes
  in electromagnetic potential.

4

• The contraction of any muscle is associated with
  electrical changes called depolarization these
  changes can be detected by electrodes attached to
  the surface of the body. Since all muscular
  contractions will be detected, the electrical
  changes associated with contraction of the heart
  muscle will only be clear if the patient is fully
  relaxed no skeletal muscles are contracting.

5

• Although the heart has 4 chambers, from the
  electrical point of view it can be thought of as
  having only 2, because the 2 atria contract
  together then the 2 ventricles contract
  together.

6
Electrical conduction of the Heart
7
Electrical conduction of the Heart

• Starts in the SA node.
• Depolarization then spreads through the atrial
  muscle fibres.
• Delay while the depolarization spreads through
  the AV node.
• Travels very rapidly down to the Bundle of His.
• Divides in the septum between the ventricles
  into right left bundle branches.
• Conduction spreads somewhat more slowly through
  the Purkinje fibres.

8
The Different Parts of The ECG
9
Times Speeds

• ECG machines record changes in electrical
  activity by drawing a trace on a moving paper
  strip.
• Standard rate of 25 mm/s use paper with
  standard sized squares.
• Large square (5mm) represents 0.2 seconds, i.e.
  200 ms.

10

• There are 5 large squares /sec, 300/min.
• So an ECG event, such as a QRS complex,
  occurring once per large square is occurring at a
  rate of 300/min.
• Heart rate 1500 No. of small squares between an
  R-R interval
• OR
• Heart rate 300 No. of large squares between an
  R-R interval

11
The 12 lead ECG

• A lead is an electrical picture of the heart.
• The electrical signal from the heart is detected
  at the surface of the body through electrodes,
  which are joined to the ECG recorder by wires. 1
  electrode is attached to each limb, 6 to the
  front of the chest.

12

• The ECG recorder compares the electrical activity
  detected in the different electrodes, the
  electrical picture so obtained is called a lead.
• The different comparisons look at the heart
  from different directions.
• Each lead gives a different view of the
  electrical activity of the heart, so a
  different ECG pattern.

13

• The ECG is made up of 12 characteristic views of
  the heart, 6 obtained from the limb leads 6
  from the chest leads.

14
The standard limb leads
15
Augmented Unipolar limb leads
16
Chest leads
17
Frontal plane leads

• Leads I, II VL look at the left lateral surface
  of the heart, leads III VF at the inferior
  surface, lead VR looks at the right atrium.

18
Horizontal plane leads

• The Chest leads look at the heart in a horizontal
  plane, from the front left side.
• V1 V2 look at the right ventricle
• V3 V4 look at the septum between the ventricles
  the anterior wall of the left ventricle
• V5 V6 look at the anterior lateral walls of the
  left ventricle

19

• The cardiac rhythm is identified from whichever
  lead shows P wave most clearly usually lead II.
  When a single lead is recorded simply to show the
  rhythm, it is called a rhythm strip, but its
  important not to make any diagnosis from a single
  lead, other than identifying the cardiac rhythm.

20
Cardiac Axis
21
(No Transcript)
22

• Leads VR II look at the heart from opposite
  directions. Seen from the front, the
  depolarization wave normally spreads through the
  ventricles from 11 o clock to 5 o clock, so the
  deflections in lead VR normally mainly downward
  (negative) in lead II mainly upward (positive).

23
(No Transcript)
24

• The average spread of the depolarization wave
  through the ventricles as seen from the front is
  called the cardiac axis. It is useful to decide
  whether this axis is in a normal direction or
  not. This can be derived most easily from the QRS
  complex in leads I, II III.

25

• When the cardiac axis is within normal limits,
  there will be a predominantly upward deflection
  in leads I, II III the deflection will be
  greater in lead II than in I or III.

26
Right axis deviation

• If the right ventricle becomes hypertrophied, it
  will have more effect on the QRS complex than the
  left ventricle, the average depolarization
  wave- the axis- will swing towards the right. The
  deflection in lead I becomes negative because
  depolarization is swinging away from it, the
  deflection in lead III becomes positive because
  depolarization is spreading towards it. This is
  called Right axis deviation.

27
Causes of Right Axis Deviation

• Right ventricular dominance due to acquired heart
  disease (Pulmonary embolism, c/c Cor pulmonale)
  congenital heart disease mainly TOF.
• Anterolateral Myocardial Infarction
• WPW syndrome
• Left posterior hemiblock When conduction is
  interrupted or delayed in the posteroinferior
  division of the left bundle branch, it is termed
  left posterior hemiblock.
• Right ventricular hypertrophy.

28
Left axis deviation

• When the left ventricle becomes hypertrophied, it
  exerts more influence on the QRS complex than the
  right ventricle. Hence the axis may swing to the
  left, the QRS complex becomes predominantly
  negative in lead III. Left axis deviation is not
  significant until the QRS deflection is also
  predominantly negative in lead II.

29
Causes of Left Axis Deviation

• Inferior wall Myocardial Infarction.
• Left Anterior Hemiblock When conduction is
  interrupted or delayed in the anterosuperior
  division of the left bundle branch, it is termed
  Left anterior hemiblock.
• Ventricular tachycardia from a focus in the apex
  of the left ventricle.
• Emphysema.
• WPW syndrome.
• Left ventricular hypertrophy

30

• The cardiac axis is sometimes measured in degrees
  though this is not clinically useful. Lead I is
  taken as looking at the heart from 0 degree lead
  II from 60 deg. lead from 90 deg. lead III
  from 120 deg. Leads VL VR look from -30 -150
  degrees respectively.

31

• The normal cardiac axis is in the range -30 deg.
  to 90 deg

32
(No Transcript)
33

• If in lead II the S wave is greater than R wave,
  the axis must be more than 90 deg away from lead
  II. In other words, it must be at a greater angle
  than -30 deg, closer to the vertical, left
  axis deviation is present. Similarly, if the size
  of the R wave equals that of the S wave in lead
  I, the axis is at right angles to lead I or at
  90 deg. This is the limit of normality towards
  the right. If the S wave is greater than the R
  wave in lead I, the axis is at an angle of
  greater than 90 deg, right axis deviation is
  present.

34
QRS Complexes in chest leads

• Leads V1 V2 look at the right ventricle leads
  V3 V4 look at the septum leads V5 V6 at
  the left ventricle.

35

• In a right ventricular lead the deflection is
  first upwards(R wave) as the septum is
  depolarized. In a left ventricular lead the
  opposite pattern is seen there is a small
  downward deflection (septal Q wave). In a right
  ventricular lead there is then a downward
  deflection (S wave) as the main muscle mass is
  depolarized. When the whole of the myocardium is
  depolarized the ECG trace returns to base line.

36

• The QRS complex in the chest leads shows a
  progression from V1, where it is predominantly
  downward, to V6, where it is predominantly
  upward. The transition point, where the R S
  waves are equal, indicates the position of the
  interventricular septum. If the right ventricle
  is enlarged, occupies more of the precordium
  than is normal, the transition point will move
  from its normal position of leads V3/V4 to V4/V5
  or sometimes V5/V6.

37
QRS is narrownormal
38
Wide QRS
39
Factors affecting the quality of ECG

• Poor electrode contact.
• Electrical interference.
• Over-calibration under-calibration
• Altered paper speed.
• An unrelaxed uncomfortable subject.

40
A Normal ECG Report

• Rate
• Rhythm
• Conduction intervals
• Cardiac axis
• A description of the QRS complexes
• A description of the ST segments T waves
• Presence of U waves, if any.

41
Normal ECG
42
Abnormalities of P waves

• P waves are best read in lead II V1. Normally P
  waves have duration of 0.12 sec (3 small squares)
  a height of 2 mm.

43
Abnormalities of P waves

• Peaked P waves They have an amplitude greater
  than 2.5 mm usually indicate right atrial
  hypertrophy. Its reflected by tall peaked P
  waves in II, III aVF is also called P
  pulmonale.
• Broad notched P waves Here the P waves have
  duration greater than 0.12 sec appears notched
  (camel humped). They usually indicate left atrial
  enlargement is also called P mitrale.

44

• Absent P waves P waves are usually absent in the
  following conditions
• Junctional extrasystole
• Ventricular extrasystole
• Junctional tachycardia
• Supraventricular tachycardia
• Ventricular tachycardia
• Atrial fibrillation

45
Ventricular Hypertrophy
46
Left Ventricular Hypertrophy (LVH)

• General criteria to assess LVH are
• If the sum of the amplitude of S wave in V1
  that of R wave in V6 exceeds 35 mm.
• If R wave in V6 is taller than R wave in V5.
• Left axis deviation.

47
LVH
48
Right Ventricular Hypertrophy (RVH)

• General criteria to assess RVH are
• Right axis deviation
• Dominant R waves in right oriented leads namely,
  aVR, V1 V2.
• RS or rS complexes in left oriented leads namely,
  I, aVL, V5 V6.
• T wave inversion in the right oriented precordial
  leads namely V1 to V4 is most marked in V1 V2
  diminishes progressively in amplitude to right,
  with associated minimal ST segment depression
  with slightly upward convexity.

49
RVH
50
Conduction Problems
51
First Degree Block

• One P wave per QRS complex.
• PR interval greater than 200 ms or 0.2 sec (1
  large square)

52
(No Transcript)
53
Second Degree Block

• Mobitz type 2 PR interval of the conducted beats
  is constant. One P wave is not followed by a QRS
  complex.

54
Mobitz type II
55
Second Degree Block

• Wenckebach type Progressive lengthening of PR
  interval. One non conducted P wave. Next
  conducted beat has a shorter PR interval than the
  preceding conducted beat.

56
Wenckebach type
57
Wenckebach
58
Second Degree Block

• 21 (or 31) block 2 (or 3) P waves per QRS
  complex, with normal P wave rate.

59
(No Transcript)
60
Third Degree (Complete) Block

• No relationship between P waves QRS complexes.
• Usually, wide QRS complexes.
• Usual QRS complex rate less than 50/min.
• Sometimes narrow QRS complexes, rate 50-60/min.

61
Third Degree (Complete) Block
62
Right Bundle Branch Block

• QRS duration gt 120 ms (3 small squares).
• RSR1 pattern.
• Usually dominant R1 wave in V1.
• Inverted T waves in V1, sometimes in V2-V3.
• Deep wide S waves in V6.

63
RBBB
64
Left Anterior Hemiblock

• Marked left axis deviation- deep S waves in II
  III, usually with a slightly wide QRS complex.

65
(No Transcript)
66
Left Bundle Branch Block

• QRS complex duration gt 120 ms.
• M pattern in V6, sometimes in V4-V5.
• No septal Q waves.
• Inverted T waves in I, VL, V5-V6 sometimes, V4.

67
LBBB
68
Bifascicular Block

• Left anterior hemiblock RBBB

69
Bifascicular block
70
Abnormalities of T wave

• T wave inversion
• Ischaemia
• Ventricular hypertrophy
• Bundle Branch Block
• Digoxin treatment
• Normally in aVR V1.

71
Abnormalities of T wave

• T wave flattening A low potassium level causes T
  wave flattening the appearance of a hump on the
  end of the T wave called a U wave.
• Peaked T waves A high potassium levels causes
  peaked T waves with the disappearance of ST
  segment. QRS complex may be widened.

72
Abnormalities of QT interval

• Normal QT interval is 450 ms

73
Abnormalities of QT interval

• Prolonged QT interval It is due to,
• Sleep
• Hypocalcemia
• a/c Myocarditis
• a/c MI
• Hypothermia
• Hypertrophic cardiomyopathy
• Complete AV block
• Cerebral injury
• Drugs- quinidine, Tricyclc antidepressants

74
Abnormalities of QT interval

• Shortened QT interval
• Digitalis
• Hypercalcemia
• Hyperthermia
• Vagal stimulation

75
Infarction

• Accurate ECG interpretation in a patient with
  chest pain is critical. Basically, there can be
  three types of problems - ischemia is a relative
  lack of blood supply (not yet an infarct), injury
  is acute damage occurring right now, and finally,
  infarct is an area of dead myocardium. It is
  important to realize that certain leads represent
  certain areas of the left ventricle by noting
  which leads are involved, you can localize the
  process. The prognosis often varies depending on
  which area of the left ventricle is involved
  (i.e. anterior wall myocardial infarct generally
  has a worse prognosis than an inferior wall
  infarct).

76
(No Transcript)
77
(No Transcript)
78
(No Transcript)
79
(No Transcript)
80
ST depression
81
Inferior wall MI
82
Anterolateral wall MI
83
THANKYOU