1. 5
The Electrocardiogram

2. The Electrocardiogram
Objectives
Define the term electrocardiogram
Discuss the basics of EKG monitoring
List the types of EKG leads
Discuss the relevance of Einthoven's triangle
Identify and explain the grids and markings on a representative strip of EKG graph paper

3. The Electrocardiogram
Objectives
Describe the relationship of the following EKG waveforms to the electrical events in the heart
P wave
PR interval
QRS complex
ST segment
T wave

4. The Electrocardiogram
A noninvasive procedure and is a graphic representation of the electrical activity of the heart
Electrocardiograph
Machine used to record the electrocardiogram, or EKG machine

5. The Electrocardiogram
EKG
Graphic tracing of electrical activity of the heart, not mechanical activity

6. The Electrical Basis of the EKG
Electrical activity is sensed by electrodes placed on the skin surface

7. The Electrical Basis of the EKG
Recorded in the form of an electrocardio-gram

8. The Electrical Basis of the EKG
Cardiac monitor depicts electrical impulses on monitor screen or oscilloscope

9. The Electrical Basis of the EKG
Electrical impulses present on the skin surface are very low voltage; impulses are amplified by an EKG machine
The printed record of the electrical activity of the heart is called a rhythm strip or an EKG strip

10. EKG Leads Electrode Leads
An adhesive pad that contains conductive gel and attaches to patient's skin
Leads
How electrodes are connected to the cardiac monitor
Three leads must have a positive, a negative, and a ground

11. EKG Leads Bipolar leads Limb leads Have one positive and one negative
Lead I
Left arm (+) and right arm (-)
Lead II
Left leg (+) and right arm (-)
Lead II is most common due to ability to visualize P wave

12. EKG Leads
Limb leads
Lead III
Left leg (+) and left arm (-)

13. EKG Leads

14. EKG Leads

15. EKG Leads

16. EKG Leads Einthoven's triangle
Imaginary inverted triangle formed around heart by proper placement of bipolar leads

17. EKG Leads Einthoven's triangle
Top formed by lead I, right side formed by lead III, and left side formed by lead II

18. EKG Leads Einthoven's triangle
Each lead represents a different look at, or view, of the heart

19. EKG Graph Paper
Leaves the machine at constant speed of 25 millimeters/seconds (mm/sec)

20. EKG Graph Paper Time Amplitude or voltage Measured on horizontal line
Measured on vertical line on graph paper

21. EKG Graph Paper

22. EKG Graph Paper Electrocardiographic Paper divided into small squares
1 mm in width
Time interval of 0.04 seconds

23. EKG Graph Paper

24. EKG Graph Paper Electrocardiographic paper
Darker lines divide paper every fifth square
Vertically and horizontally
Large squares measure 5 mm in height and width
Represents time interval of 0.20 seconds
Five small squares in each large square

25. EKG Waveforms
Wave or waveform refers to movement away from the baseline or isoelectric line (beginning and ending of all waves)

26. EKG Waveforms Positive deflection Negative deflection
Above isoelectric line
Negative deflection
Below isoelectric line

27. EKG Waveforms
Electrical impulse leaves SA node, produces waveform on graph paper
One complete cardiac cycle = P, Q, R, S, (QRS complex) and T wave

28. P Wave First wave produced by electrical impulse from SA node
Smooth, rounded upward deflection

29. P Wave
Depolarization of left and right atria
0.10 seconds in length

30. PR Interval
Time impulse travels from SA node through internodal pathways in atria toward ventricles

31. PR Interval Time interval from start of P wave to start of QRS
0.12–0.20 seconds in length

32. QRS Complex
Consists of Q, R, and S waves

33. QRS Complex
Represents conduction of impulse from bundle of His through ventricular muscle
Ventricular depolarization

34. QRS Complex
Q wave
First downward (negative) deflection

35. QRS Complex R wave First upward (positive) deflection
Largest deflection seen in Leads I and II

36. QRS Complex S wave Measures less than 0.12 seconds (3 small boxes)
Downward deflection after R wave
Measures less than 0.12 seconds (3 small boxes)

37. ST Segment
Time interval during which ventricles depolarized and repolarization of ventricles begin

38. ST Segment Isoelectric or consistent with baseline
Elevation and/or depression of ST segment indicative of an Acute Myocardial Infarction

39. T Wave
Follows ST segment
Represents ventricular repolarization

40. T Wave Slightly rounded, positive deflection
Resting phase of cardiac cycle

41. Summary of EKG Waveforms
P wave
Atrial depolarization
QRS complex
Ventricular depolarization, atrial repolarization

42. Summary of EKG Waveforms
T wave
Ventricular repolarization