Ecg

1. Electrocardiography
ECG
Dr. Malik Muhammad Ali Awan
Assistant Professor – Physical Therapy
MSc. Cardiopulmonary Physical Therapy, DPT
Intensive Care Physical Therapist

2. ECG
“An ECG is the recording (gram)
of the electrical activity (electro)
generated by the cells of the heart (cardio)
over time.”
Useful in diagnosis of…
▫ Cardiac Arrhythmias (gold standard)
▫ Myocardial ischemia and infarction
▫ Electrolyte disturbances
▫ non-cardiac diseases (e.g. pulmonary embolism)

3. The Normal ECG
Note: * “T” wave is inverted in leads aVR and V1
* “QRS” is inverted in leads aVR, V1 & V2

4. Normal conduction pathway:
• SA node -> atrial muscle -> AV node -> bundle of His -> Left
and Right Bundle Branches -> Ventricular muscle

5. 1. SA node
2. AV node
3. bundle of His
4. bundle branches
5. Purkinje fibers

6. Recording the ECG
12 leads ECG include
• 6 limb leads ( 3 standard leads, 3 unipolar leads)
• 6 chest or precordial leads
• Each lead incorporates two electrodes measuring
the potential or voltage difference between them.
• The positive electrodes detects the electrical impulse
while neutral electrodes completes the circuit.
• The ECG monitor placed in the circuit detects
electrical activity.

7. A P
I

8. Standard limb leads
• LOCATION:
▫ Lead I: the exploring electrode is attached to left arm and neutral
to the right arm
▫ Lead II: exploring electrode to the left leg and the neutral
electrode to the right arm
▫ Lead III: exploring electrode to the left leg and the neutral
electrode to the left arm.
• ASSESSMENT:
▫ Lead I: Lateral surface of the heart
▫ Lead II: Inferior surface of the heart
▫ Lead III: Inferior surface of the heart

9. Unipolar limb leads
LOCATION:
Exploring electrode is on the rt leg and neutral electrode
on all the other limbs
▫ Lead AvR attached to right arm
▫ Lead AvL attached to left arm
▫ Lead AvF attached to left leg
• ASSESSMENT:
▫ AvR - (R) side of the heart
▫ AvL - (L) side of the heart
▫ AvF – Inferior aspect of the heart (Chiefly Lt. Ventricle)

10. Chest leads
• LOCATION:
▫ V1 4th IC space (R)
▫ V2 4th IC space (L)
▫ V3 b/w V2 and V4
▫ V4 5th IC space mid-clavicular line
▫ V5 5th IC space anterior axillary line
▫ V6 5th IC space mid-axillary line
ASSESSMENT:
▫ V1 and V2 assess the right ventricle
▫ V3 and V4 interventricular septum
▫ V5 and V6 anterior and lateral aspect of the heart

12.  3 distinct waves
are produced
during cardiac
cycle:
 P wave caused by
atrial
depolarization
 QRS complex
caused by
ventricular
depolarization
 T wave results
from ventricular
repolarization
ECG
Fig 13.24
13-63

13. COMPONENTS OF THE ECG
P – Wave:
• Represents atrial depolarization
• Duration: b/w 0.08 - 0.12 sec
QRS complex:
• Represents depolarization of ventricles
• Duration: b/w 0.08 - 0.10 sec
T – wave:
• Represents ventricular repolarization
• Duration: 0.10 to 0.25 seconds
U – wave:
• Represents late repolarization after the T – wave
• Of little importance but needs to be recognized so as not to confuse
it with other components

14. COMPONENTS OF THE ECG
P – R interval:
• starts at the beginning of the P wave and ends at the onset of
the QRS
• Represents the time lapse of the impulse travelling from the SA
node through the AV node on its way to the ventricles.
• No m/s contraction during this event.
• Duration: 0.12 and 0.2 sec
S – T segment:
• starts from the end of the QRS and terminates at the onset of
the T wave.
• Following completion of ventricular depolarization, there is a
period of electrical inactivity represented by the S – T segment.

17. HOW TO READ ECG PAPER
• 1 small box represents 0.04 seconds or 1mm
• 1 large box represents 0.2 seconds or 5mm
• 5 large box = 1 second 25mm
• 30 large box = 6sec
• 300 large box = 1 minute
• PR interval (0.20sec) = 1 big box
• QRS complex (0.12 sec*) = 3 small boxes
The normal running speed for recording an ECG is
25mm/sec

18. Evaluating the ECG Strip
 What is the rate and pattern (regularity) of the rhythm? If the R-R interval, that
is, the distance between successive R-waves, is inconsistent, is the pattern
irregular?
 Does a P-wave precede every QRS complex? This indicates appropriate atrial
activity.
 Is there a QRS complex after every P-wave? This indicates appropriate conduction
of impulses from atria to ventricles.
 What is the P-R interval? A P-R interval of greater than 0.20 seconds indicates
delay in conduction from atria to ventricles.
 Is the QRS complex of normal duration and morphology (shape)? A QRS complex
greater than 0.12 seconds indicates either that an impulse arose within a ventricle
or was conducted abnormally through the ventricular conduction system.
 By answering each of these questions, the tendency to "eyeball" the rhythm and
make a quick but inaccurate assessment is avoided.

19. Summary
• SA node atrial depolarization slight delay in the A V node, 
ventricular depolarization normal sinus rhythm (Figure 1 1-8).
• P-wave precedes every QRS complex and every P-wave is, in turn,
succeeded by a QRS complex. This occurs within an interval of 0.20
seconds (one large box), as determined by the P-R interval.
• The QRS complexes occur within a range of 0.08 to 0.10 seconds (3
small boxes), indicating that ventricular impulse conduction and
depolarization is occurring in a normal interval.
• The positively deflected T-wave indicates normal ventricular
repolarization.

20. Determination of Heart Rate
Method 1
• Find an R-wave located on or near a heavy
vertical line. Proceeding to the left of that R
wave, for each subsequent heavy vertical line,
assign the following numbers: 300 for the first
heavy line encountered, 150 for the next
followed by 100, 75, 60, 50, and 42 (Figure 11-5).

21. Determination of Heart Rate

22. Method 2
• Count the number of R-waves within the 6-second recording, and
multiply by 10.
• In Figure The rate of this irregular rhythm is estimated at 60 BPM.

24. Evaluation of Rhythms

25. Junction Rhythm
• Occurs when the AV junction takes over as
pacemaker
• May be considered an escape rhythm
• Absence of P wave before QRS
• Failure of SA node to functioning, sinus node
disease, Increase in vagal tone, infarction and
sever ischemia of the atrial conduction system

26. Sinus bradycardia
• Sinus bradycardia is a sinus rhythm
occurring at a rate of less than 60 BPM
(Figure 11-10).
• This rhythm may significantly reduce
cardiac output, causing hemodynamic
compromise, manifested by hypotension
or symptoms such as dizziness,
lightheadedness, or syncope.

28. Sinus tachycardia
• Sinus tachycardia is a sinus rhythm
occuring at a rate of greater than 100 BPM
(Figure 11- 1 1).
• Sinus tachycardia, increases myocardial
oxygen demand and the workload on the
heart. This may initiate or exacerbate
ischemia in the presence of coronary
artery disease (CAD).

31. Supraventricular tachycardia (SVT)
• Heart rate is rapid exceeding 150 BPM.
• The tachycardia may be sustained, lasting hours or even days, or may be
"paroxysmal" (PSVT), appearing abruptly and spontaneously reconverting
to the previous rhythm within seconds or minutes.
• The P-wave is often not visible and the duration of the QRS complexes
occurs within an appropriate interval. The R-R interval, however, is
markedly shortened.
• Symptoms associated with inadequate cardiac output, such as dizziness,
lightheadedness, and syncope may ensue.

32. SVT
• P – waves not
identifiable.
• Duration of QRS
normal.
Figure 11-13 demonstrates supraventricular
tachycardia at a rate of 190 BPM.

33. SUPRA VENTRICULAR TACHYCARDIA
• AVNRT
▫ An abnormal fast heart
rhythm that originates from a
location within the heart
above the bundle of His.
▫ occurs when a reentrant
circuit forms within or just
next to the atrioventricular
node
• AVRT / WPW syndrome
▫ extra electrical pathway between the
heart's upper and lower chambers.
▫ WPW the accessory pathway is often
referred to as the Bundle of Kent, or
atrioventricular bypass tract, located
below bundle of His or at the end of
conduction system
▫ Tachyarrythmia can be facilitated by
the formation of a reentry circuit
involving the accessory pathway,
atrioventricular reentry tachycardias
(AVRT)

34. AVNRT

35. AVRT

36. Atrial flutter
• P-waves are replaced by F-waves that have a
distinctive morphology often referred to as a
"saw tooth" or "picket fence" appearance.
• Of clinical importance is the ratio of atrial to
ventricular conduction and whether or not the
patient is hemodynamically stable.
• Atrial rate is in between 200 and 310 bpm

37. Atrial Flutter

38. Atrial fibrillation
• Atrial fibrillation is characterized by inconsistent, irregular R-R intervals with an
absence of true P-waves.
• Atrial rate is in between 400 to 600 bpm
• P-waves may be replaced by multiple, fibrillatory F waves of varying
configuration.
• The atria, are not pumping effectively which cause impair ventricular contraction.
• Figure 11-7 illustrates atrial fibrillation with a "controlled," that is, less than 100
BPM, ventricular response.
• Pulse monitoring of an individual in atrial fibrillation reveals an irregularly
irregular pattern.

39. Atrial Fibrillation

40. PRE – MATURE VENTRICULAR COMPLEXES
• A premature beat arising from an ectopic focus within the
ventricles.
• Groups of pacemaker cells throughout the conducting system
are capable of spontaneous depolarization.
• The rate of depolarization decreases from top to bottom: fastest
at the sinoatrial node; slowest within the ventricles.
• Ectopic impulses from subsidiary pacemakers are normally
suppressed by more rapid impulses from above.
• However, if an ectopic focus depolarizes early enough — prior to
the arrival of the next sinus impulse — it may “capture” the
ventricles, producing a premature contraction.

41. PATTERNS
▫ Bigeminy — every other beat is a PVC.
▫ Trigeminy — every third beat is a PVC.
▫ Quadrigeminy — every fourth beat is a PVC.
▫ Couplet — two consecutive PVCs.
▫ Triplet — three consecutive PVCs.
• PVCs are a normal electrophysiological phenomenon not
usually requiring investigation or treatment.
• Frequent PVCs may cause palpitations and a sense of the
heart “skipping a beat”.

42. PVCs

44. Ventricular tachycardia
• This is a serious and potentially lethal arrhythmia that may
require emergency measures be undertaken.
• During v-tach all complexes are ventricular in origin.
• V –tach sometimes occurs in "runs" of three or more ectopic
complexes followed by reversion to the baseline rhythm, or it
may be sustained. Effective circulation may be preserved, or it
may be seriously compromised or absent in sustained v-tach.
• QRS duration greater then 0.12 s
• P and T waves are difficult to distinguish.
• PR interval is not measureable

45. VT - Polymorphic

46. VT - Monomorphic

47. Ventricular fibrillation
• It is characterized by disorganized, simultaneous firing of multiple, ectopic
ventricular foci; there is no organized rhythm (Figure 11-21).
• Effective ventricular contraction ceases and cardiopulmonary resuscitation is
indicated until defibrillation is available.
• If not successfully treated, v-fib may further degenerate into asystole, which
indicates complete absence of ventricular electrical activity (Figure 11-21).
• Asystole may also occur as a primary event. This is known as "flat line" rhythm. Like
ventricular fibrillation, asystole requires that cardiopulmonary resuscitation begin
immediately to save the patient's life.
• are must be taken to distinguish an apparent lethal arrhythmia from lead
disconnection or movement artifact.
• during activity or exercise, movement artifact may easily be mistaken for v-tach.

48. VF

49. Conduction Blocks
• The propagation of a cardiac impulse may be inhibited or
terminated along the conduction pathway.
• Blockage can occur at the sinus node, between the atria
and ventricles, Or within the ventricular conduction
system.
• Sinus block occurs if the impulse cannot propagate beyond
the sinus node. In this case, the AV junction usually takes
over as the pacemaker, and a junctional rhythm is seen
with the absence of P-waves.
• More common are the AV blocks. They are ranked as first-
, second, or third-degree, depending on the extent of delay
or obstruction of the cardiac impulse between the atria
and ventricles.

50. First-degree A V block
• First-degree A V block is characterized by a
prolongation of the P-R interval beyond its normal
0.2 seconds.
• Remember that the P-R interval is measured from
the beginning of the P-wave to the beginning of the
QRS complex.
• Each impulse is delayed between the atria and
ventricles but each eventually reaches the
ventricular conduction system resulting in a normal
QRS complex.

51. 1st degree heart block
• Husband comes home late every night at the
same time, but he
ALWAYS comes home!!!

52. First-degree A V block

53. 2nd Degree (Mobitz type 1)
• PR Interval gets longer & longer till QRS is
dropped

54. 2nd Degree (Mobitz type 1)
• Husband comes home later and later and later
until one night he doesn’t come home at all, then
the pattern starts all over again!!!

56. 2nd Degree (Mobitz Type 2)
• P wave is on time but randomly drops QRS

57. 2nd degree mobitz 2
• Husband comes at the same time every night,
but there are some nights that he just doesn’t
come home!!!

59. Third degree A V block
• Third degree A V block or complete heart block is also known as AV
dissociation.
• Two independent functioning pacemakers within a single heart,
impulses originating from purkinje system
• In this rhythm (Figure 11-25), P-waves are present, but there is no
relationship between P-waves or QRS complexes.
• P-waves may be superimposed on QRS complexes, but none of the sinus
impulses are conducted to the ventricles
• the atria and ventricles are contracting independently of each other.
• In most cases of third degree block, treatment now includes
implantation of an artificial pacemaker.

60. 3rd Degree block
• Husband and wife are finally seprated but can’t
afford to move out of their house because of the
bad economy.
• As a result, they are stillliving under the same
roof, but leading two separate lives!!! It
appears as if they’re still married, but they’re
not! There is no communication between them

62. MYOCARDIAL ISCHEMIA OR INFARCTION
• During myocardial ischemia, blood flow to a portion
of myocardium is compromised, resulting in
alteration of myocardial metabolism. ST
Depression and or T - Inversion
• If full thickness of heart wall commonly of left
ventricle is depleted of its perfusion this is
transmural infarction,
• S-T segment shift has significant diagnostic value.
For example S-T segment elevation (Figure 11-
26) is associated with transmural Ml.

63. MYOCARDIAL ISCHEMIA OR INFARCTION

64. MYOCARDIAL ISCHEMIA OR INFARCTION
• whereas S-T segment depression is
associated with non transmural or
subendocardial MI where percentage of
wall is effected (NOT FULL THICKNESS)
• Onset of S-T segment depression during
activity is often considered diagnostic for
myocardial ischemia. Figure 11-27 is an
example of exercise-induced S-T segment
depression observed in one lead during
exercise.

65. ST DEPRESSION

66. MI - ECG changes with time
The change that occur on the ECG depict the changing state of
myocardium:
• Within minutes or hours, the ST segment becomes elevated in the
leads facing the infarction.
• Within hours or days, there is development of broad and deep
Q –waves with R wave reduction and an inverting T wave.
• Abnormal Q wave is the definitive diagnosis for
transmural infarction. (Greater than 25% depth of QRS
and having width of 1 large box)
• Within a week or more, there is return of S-T segment to baseline
but the other signs remain same.
• Months later, there is a possible gradual return of the T wave but
persistent abnormal Q waves.

69. BUNDLE BRANCH BLOCK
• There is disturbance in the intraventricular
conduction.
• QRS complex wide
• 2 peaks on R – wave
• P – wave, P-R intervals and heart rate normal.
Depending on which leads demonstrates the changes,
it can be established if the block is a left or right
bundle branch block

70. Ventricular Hypertrophy
• In left ventricular hypertrophy there are
abnormally large R waves (1.37inch / 34.7mm)
in V4 and V6
• In right ventricular hypertrophy large R waves in
V1 and V2
• This may be accompanied by signs of heart
muscle strain such as ST depression and T wave
inversion.

71. Ventricular Hypertrophy