1. Cardiovascular Monitoring Electrocardiogram
Dr.noha elsayed

2. Electrocardiography
Electrical activity is recorded by electrocardiogram (ECG)
P wave corresponds to depolarization of SA node
QRS complex corresponds to ventricular depolarization
T wave corresponds to ventricular repolarization
Atrial repolarization record is masked by the larger QRS complex
Cardiovascular System: Intrinsic Conduction System
, Cardiovascular System

3. Electrocardiography
Figure 18.16
Chapter 18, Cardiovascular System

4. Isoelectric line
No electrical activity baseline

5. EKG Records 1. Amount of voltage generated by ht – vertical scale
2. Time required for voltage to travel thru ht – horizontal scale

6. ECG Interpretation What is your approach to reading an ECG? Rate
Rhythm
Axis
P wave
PR interval
QRS complex
QT interval
ST segment – T wave
SLIDE STARTS WITH QUESTION ONLY
Ask interns about their method for interpreting an ECG.
Emphasize the importance of interpreting an ECG always in the same order so that nothing is missed.
Question will appear first in presentation, then answers.

7. EKG Interpretation: 8 criteria
1. What is the rate?
Quick estimate:
Count # R waves in a 6 second strip x 10
6 second strip = 3 “tic” marks
Square Counting: A

8. Role of 300
Take the number of “big boxes”between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the rate
Although fast, this method only works for regular rhythms.

9. 10 Second Rule
As 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.

10. Rythm 2. Is rhythm regular or irregular?
Measure distance between RR interval
Measure throughout full 6 second strip

11. Axis 3.Left or right axis deviation? Look at limb leads I and aVF.
Normal: I +, aVF +
LAD: I +, aVF –
RAD: I -, aVF +
Left Axis Deviation (LAD)
Right Axis Deviation (RAD)

12. Axis Deviation

13. QRS-axis

14. 4-P Wave First component of a normal ECG
Represents the spread of electrical activity over the atrium, atrial depolarization. The normal depolarization begins at the sinoatrial (SA) node near the top of the atrium. Because of the top-to-bottom, right-to-left path, the P wave is normally largest in Lead II
Configuration: usually rounded and upright in all leads except R
Amplitude is usually 2-3 mv in any lead

15. Are P waves present?
Should be 1:1

17. Abnormal rhythms with P waves

18. 5. What is the PR Interval? PRI

19. PR Interval
Measured from the beginning of the P wave (atrial depolarization) to the beginning of the QRS complex (ventricular depolarization)
Represents the time it takes for an impulse to travel from the SA node through the atria and the AV node
Normally between 0.12 to 0.20 seconds in duration
If prolonged, > 0.20 seconds
indicates conduction delay through the AV node
and is called a 1st degree AV block

20. 6. What is the width of QRS complex?
Normal QRS duration is 0.06 to 0.12 seconds

21. QRS Complex
Represents activation of the ventricles, ventricular depolarization
Special conducting bundles spread the wave of depolarization rapidly over the bundles
May have one, two or all three components : Q R S
Q wave is the first negative wave after the P wave and before the R wave. The Q wave represents activation of the ventricular septum
R wave is the first positive wave after the P wave.
Most of the ventricle is depolarized during the R wave.
S wave is the negative wave after the R wave.
Lengthening of the QRS indicates some blockage of the electrical conduction system either due to ischemia, necrosis of the conducting tissue, electrolyte imbalance or hypothermia

22. Sinus Rhythm Impulse originates in SA node (normal pacemaker site)
Normal Sinus Rhythm - NSR
Regularity – regular
Rate - 60 – 100 / minute
P waves = 1:1
PRI =
QRS = .12 or <

23. 7-Q-T Interval
QT interval represents total ventricular activity. It is the summation of ventricular depolarization to repolarization
Can vary with heart rate
Measured from the beginning of the Q wave to the end of the T wave
Corrected QT interval (QTc) takes heart rate into account and provides various normal values based on the rates
Rule of thumb – QT interval should be less than half the preceeding R-R interval
The U wave represents repolarization of the Purkinje fibers but isn’t always seen on paper. A prominent U wave may be caused by hypercalcemia or hypokalemia

24. 8.ST segment & T wave
ST segment – Elevation or depression indicates ischemia. Figure on right: Concave– Normal  smile. Convex – MI  frown.
T wave - can diagnosis ischemia, hyperkalemia
Now we are ready to start an ECG.
a case day is workable.

25. Normal Values - HR dependent, cave: long QT syndrome!
PR interval: s
QRS complex: s
QT interval: < 0.44 s
- HR dependent, cave: long QT syndrome!
ST segment changes:
- significant if > 1mm in limb leads, > 2mm in precordial leads
Q waves:
significant if > 1/3 of total QRS complex