2. 2
Willem Einthoven (21 May
1860 – 29 September 1927) was
a D u t c h d o c t o r a n d
physiologist. He invented the
first practical electrocardiogram
(ECG or EKG) in 1903 and
received the Nobel Prize in
Medicine in 1924 for it ("for the
discovery of the mechanism of
the electrocardiogram")
Who invented ?
3. 3
Definition of ECG
Electrocardiogram: A recording of the electrical
activity of the heart. Abbreviated ECG and EKG. An
ECG is a simple, noninvasive procedure. Electrodes
are placed on the skin of the chest and connected in a
specific order to a machine that, when turned on,
measures electrical activity all over the heart.
4. 4
Course Objectives
• Cardiac arrhythmias
• Conduction defects
• Ischemia or MI
• Chamber enlargement
• Hypertrophy of the heart
8. CARDIAC ACTION POTENTIAL
Phase 2
• Plateau phase
• Calcium continues to move in
to the cell
• Potassium start to move out
of the cell
8
9. CARDIAC ACTION POTENTIAL
Phase 3
• Calcium channel close
• Potassium moves quickly out of the cell
• Until middle of phase 3 absolute
refractory period
• At the end of Phase 3, a strong impulse
could initiate a beat as the cell is now in
its relative refractory period.
9
29. Mechanical events
29
U wave
• Repolarization Of purkinje fibre
• The electrical physiology behind a U wave is not clearly under- stood.
• Although U waves have been seen in normal individuals, the presence
of a U wave is more commonly associated with hypokalemia or the
administration of medications such as amiodarone or digoxin
36. 36
Pacemakers of the Heart
○ SA Node - Dominant pacemaker with an
intrinsic rate of 60 - 100 beats/ minute.
○ AV Node - Back-up pacemaker with an
intrinsic rate of 40 - 60 beats/minute.
○ Ventricular cells - Back-up pacemaker
with an intrinsic rate of 20 - 45 bpm.
39. 39
Step 1: Calculate Rate
○ Option 1
● Count the # of R waves in a 6
second rhythm strip, then multiply
by 10.
● Reminder: all rhythm strips in the
Modules are 6 seconds in length.
Interpretation? 9 x 10 = 90 bpm
3 sec 3 sec
40. 40
Step 1: Calculate Rate
○ Option 2
● Find a R wave that lands on a bold line.
● Count the number of large boxes to the
next R wave. If the second R wave is 1
large box away the rate is 300, 2 boxes -
150, 3 boxes - 100, 4 boxes - 75, etc.
(cont)
R wave
42. Step 1: Calculate Rate
○ Option 3
Count the number of small boxes
within an RR interval and divide 1500 by
that number.
Eg: if there are 20 small boxes, the heart
rate is 1500/20= 75
42
43. 43
Step 2: Determine regularity
○ Look at the R-R distances (using a caliper
or markings on a pen or paper).
○ Regular (are they equidistant apart)?
Occasionally irregular? Regularly irregular?
Irregularly irregular?
Interpretation? Regular
R R
44. 44
Step 3: Assess the P waves
○ Are there P waves?
○ Do the P waves all look alike?
○ Do the P waves occur at a regular rate?
○ Is there one P wave before each QRS?
Interpretation? Normal P waves with 1 P
wave for every QRS
47. 47
NSR Parameters
○ Rate
60 - 100 bpm
○ Regularity
regular
○ P waves
normal
○ PR interval
0.12 - 0.20 s
○ QRS duration
0.04 - 0.12 s
Any deviation from above is sinus
tachycardia, sinus bradycardia or an
arrhythmia
