1. Understanding EKGs

2. Vectors A vector has direction A vector has magnitude
Vectors can be added or summated

3. Vector A
Vector B
Resultant Vector
A + B

26. EKG 2

27. EKG 3

30. Normal Waves of the EKG P wave – atrial depolarization
Ta wave – atrial repolarization
Q wave – initial negative deflection from ventricular depolarization
R wave – first positive deflection from ventricular depolarization
S wave – first negative deflection following the R

31. Normal Waves Con’td R’ wave – second positive deflection
S’ wave – second negative deflection following R
T wave – ventricular repolarization

32. P Wave Characteristics
Duration is < 0.12 seconds
Amplitude is < 4 mm
Contour is normally gently rounded, not notched or peaked
Normally upright in I, II, aVF
Inverted in aVR

33. QRS Characteristics Normal duration is < 0.11 seconds
Amplitude (R or S wave) is > 5 mm and < 30 mm
Dominantly positive in I, II, aVF
Dominantly negative in aVR

34. T Wave Characteristics
Same polarity as dominant wave of QRS
Positive in I, II, aVF
Inverted in aVR
Asymmetrical, ascending more slowly than descending

35. Segments and Intervals of the EKG
P-R Interval
From beginning of P to beginning of QRS
Measures time taken by impulse to travel from SA node to ventricular fibers
Normal duration seconds
ST Segment
From end of QRS to beginning of T
Should be isoelectric (on baseline)