Steve Selig 1

1
ECG electrophysiological origins

• SAN reaches threshold before all other pacemakers
• 0.1 sec delay in internodal pathways to enable
  full atrial activation before any ventricular
  systole
• Bachmann bundle and His-Purkinje fibres
  accelerate and co-ordinate the spread of
  excitation through the left atrium and both
  ventricles, respectively

2
ECG electrophysiological origins

• Depol wave in direction of an electrode ? UPWARD
• P wave average vector for atrial depol
• Q wave depol of ventricular septum (L ? R and
  upwards)
• R wave depol of main septal wall (R ? L and
  downwards)
• S wave depol of L and R free walls (upwards)
• SAN, AVN. Bachmann Bundle and His-Purkinje waves
  not visible

3
Cardiac Cycle
4
Cardiac contraction ? cardiac cycle
5
Tourniquet effect of systole on coronary flow

• ?? coronary flow during isovolumetric systole
• ? coronary flow during ejectile phase of systole

6
10 electrodes 12 leads!!
avR
avL
V1
V6
10 electrodes
avF
RL (earth)
7
10 electrodes 12 leads!!
I
avR
avL
ve
-ve
-ve
-ve
V1
V6
II
III
ve
ve
12 leads
avF
RL (earth)
8
Determining the ECG vector
I
7-25
ve
-ve
0
25
-25
-25
-ve
-ve
II
III
0
0
ve
ve
12-210
15-213
25
9
ECG Interpretations

• Look at the ECG according to the following
  criteria (in order)
• 1. atrial rhythm regular/irregular?
• 2. atrial rate count P waves, eg 80 bpm
• 3. sinus rhythm are the ventricles driven by the
  atria? Yes/No
• 4. ventricular rhythm regular/irregular?
• 5. ventricular rate count QRS, eg 60 bpm

10
ECG Interpretations

• Look at the ECG according to the following
  criteria (in order)
• 6. P waves are they visible? Are they upright in
  I,II, aVF and down in aVR? Are they normal sized,
  too big (eg mitral stenosis, MS), biphasic (eg
  premature atrial contraction, PAC), notched (eg
  MS) or multiform (eg wandering pacemaker)?
• 7. PR interval should be 0.12-0.20 secs (3-5
  little squares) too short pre-excitation, too
  long heart block.

11
ECG Interpretations

• Look at the ECG according to the following
  criteria (in order)
• 8. QRS width should be 0.04-0.12 sec too wide
  bundle branch block.
• 9. Q wave is it 25 of R wave? If so this
  indicates old infarct.
• 10. QRS complex first ? is Q, first ? is R,
  first ? after R is S. Then R', S', etc. (these
  indicate problems, eg. bundle branch block). QRS
  voltage should be at least 0.5 volt (cm) in limb
  leads not more than 2.5-3.0 volt (cm) in V1-V6.

12
ECG Interpretations

• Look at the ECG according to the following
  criteria (in order)
• 11. ST segment should be isoelectric. ST
  depression indicates angina (common) or
  endocardial infarction (occasionally). ST
  elevation indicates possible infarction.
• 12. T wave should be up in I, II, aVF, V1-6 and
  down in aVR.
• 13. U wave not always seen.

13
ECG rhythms

• Sinus (SAN) rhythms (eg sinus tachycardia sinus
  block)
• Atrial rhythms (eg paroxysmal atrial tachycardia
  atrial fibrillation)
• Junctional (AVN) rhythms (eg junctional beats
  heart block)
• Ventricular rhythms (eg ventricular tachycardia
  ventricular ectopic)

14
ECG what to do about some rhythms
15
ECG what to do about some rhythms
Green
Green
16
ECG what to do about some rhythms
Ventricular bigeminy the VPB collides with the
normal SAN-atrial AP
17
ECG what to do about some rhythms
Green
18
ECG what to do about some rhythms
Sinus rhythm with sinus block green
19
ECG what to do about some rhythms
Sinus rhythm with sinus arrest green
20
ECG what to do about some rhythms
Sinus rhythm with premature atrial contraction
(PAC) green
taller T wave premature P embedded
Sinus rhythm with non-conducted PAC green
P wave without a following QRS
21
ECG what to do about some rhythms
22
ECG what to do about some rhythms
10 Heart Block prolonged PR no dropped beats
20 Heart Block (Mobitz Type I) gradual
lengthening of PR ? dropped R
23
ECG what to do about some rhythms
20 Heart Block (Mobitz Type II) normal or
prolonged PR ? with dropped Rs
30 Heart Block total dissociation of P and R
waves
24
ECG what to do about some rhythms
no Ps irregular vent rate normal QRS
morphology
Atrial flutter IHD, CHF Red sawtooth atrial
waves with a 41 or 21 protective AV block
(typically ? atrial rate 300 ventricular rate
75 or 150)
25
Atrial Fibrillation

• Factors that predispose to aF
• shortened atrial refractory period
• slow atrial conduction
• increased atrial size (eg heart failure, mitral
  stenosis)

26
ECG what to do about some rhythms
pacemaker spikes
delta waves
27
Pre-excitation syndrome (eg Wolf-Parkinson-White)
Exercise
Rest
X
Re-entrant tachycardia
Delta waves
28
ECG what to do about some rhythms
mean RSR/ vector
left bundle blocked here
29
ECG what to do about some rhythms
left bundle blocked here
30
ECG what to do about some rhythms
Acute myocardial infarction ST? IHD Red
31
Acute myocardial infarction
normal
injury
necrosis ?Q injury ?ST ischaemia ?T
ischaemia
necrosis
Electrode
32
Coronary Arteries
Posterior View
Anterior View
33
Acute Myocardial Infarction (AMI)
34
ST? and ST?
ST? Ischaemia (angina) injury is endocardial
ST? Acute myocardial infarction (heart
attack) necrosis is epicardial
35
ECG what to do about some rhythms
R
R
S
S
Normal QRS
Q
Acute myocardial infarction ST? IHD Red
36
ECG what to do about some rhythms
37
ECG what to do about some rhythms
38
Interpreting exercise ECGs
Normal rest
Normal exercise pseudo ST ? due to early atrial
repol ? P and ? QRS voltages ? PQ, ? QT and ? TQ
intervals
Ischaemic heart disease exercise ST
? susceptibility to dysrhythmias
39
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
40
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
41
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
42
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
43
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
44
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
45
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
46
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
47
What is this rhythm?
atrial rhythm atrial rate ventricular
rhythm ventricular rate sinus rhythm P
waves QRS waves PR interval ST segment T
waves Interpretation
48
Drugs and effects on HR, BP, ECG and exercise
response
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Drugs and effects on HR, BP, ECG and exercise
response
50
Drugs and effects on HR, BP, ECG and exercise
response
51
Drugs and effects on HR, BP, ECG and exercise
response
52
Drugs and effects on HR, BP, ECG and exercise
response
53
Drugs and effects on HR, BP, ECG and exercise
response
54
Drugs and effects on HR, BP, ECG and exercise
response