Electrocardiogram ( Cardiovascular Physiology )

1. ECG
Dr. Mohammed AL-Mojtaba A. Awad

2. Objectives :
• Introduction
• Basic ECG
+Definition , Leads , ECG paper
+Waves & Intervals
• Advanced ECG
+Steps for Interpretation
+Abnormalities

3. Introduction
• Conduction System of the heart
• Electrophysiology of the heart

5. Electrophysiology of the heart
• Electrical impulses generated SA Node .
• Transmitted to nearby muscle cells & then
through internodal pathway it passes from
atria to AV Node .
• Internodal delay occurs in the AV node before
Conducting impulses into the Bundle of His
• From bundle of His Electrical potential passes
through interventricular septum to Right
Bundle branch & Left Bundle branch .

6. • Then it passes to Purkinji system ( fast
Conducting pathway) to the rest of the
Ventricular System .

7. Basic ECG
• Definition
• ECG Electrodes
• ECG Leads
• ECG Paper
• Waves & intervals
• Axis

8. Basic ECG
• Definition :
It is an instrument that is used for recording of
the electrical Activity in the Heart that occurs
during Cardiac Cycle by ELECTRODES places
on the Surface of the Body .
It is first discovered by Dutch physiologist,
Einthoven Willem, who is considered the
father of electrocardiogram (ECG).

9. Electrodes :
• There two types of electrodes ( Limb
Electrodes & Chest Electrodes )

10. Leads Recorded by this Electrodes :
• They are :
limb leads
+Unipolar (augmented) >
aVR,aVL,aVF
+Bipolar >> I , II , III
Chest leads
V1 , V2 , V3 , V4 , V5 , V6

13. ECG Paper

14. Leads arrangement

16. Squares of the ECG paper
• The paper contains a number of Large Squares
• Each large square contains 25 small squares (
5 x 5 ) .
• Each large square = 0.2 seconds Duration &
0.5mV Amplitude >>>>>
• So each Small Square = 0.04 seconds Duration
& 0.1mV Amplitude
• Cardiac Cycle Duration is 0.8 Seconds >> 4
large Squares .

17. Waves & Intervals
• Waves :
P wave = Atrial Depolarization
QRS Complex = Ventricular Deploarization
T wave = Ventricular Repolarization
U wave (sometimes) = papillary muscles
repolarization

18. • Intervals
PR Interval = Atrial Activity
ST segment = Plateau of Ventricular
Depolarization
QT Interval = Ventricular activity

23. Normal ECG

25. Cardiac Axis

26. • In healthy individuals axis lies between -30 &
+90
• The overall direction of electrical activity is
towards Lead I , II & III
• As a result you see +ve deflection in all these
leads
• Also the most –ve deflection can be seen in
aVR, due to aVR, looking at heart in opposite
direction to overall electrical activity .

27. So when you would determine the axis
look at Lead I & aVR

31. Advanced ECG
• Interpretation of ECG Paper
:
Interpretation of ECG
Paper
Name , Date ,
Calliberation , paper speed
+ Rate
+ Rhythm
+Axis
+P wave
+PR interval
+QRS Complex
+ST Segment
+T wave
+QT Interval

32. Rate

35. Rhythm

37. Axis

40. Abnormalities
• Abnormality of Rate
• Abnormality of Rhythm
• Axis Deviation
• Conduction Defects
• Ischemic Changes

41. THANQ