1. Basic Cardiac ElectrophysiologyBasic Cardiac Electrophysiology
and ECG Conceptsand ECG Concepts
胡瑜峰醫師胡瑜峰醫師
台北榮總心臟 科內台北榮總心臟 科內

2. OutlineOutline
• Ion current, action potential and cardiac
conduction
• Surface EKG
• Intracardiac mapping
• Mechanism and catheter ablation

3. Electrical System of the HeartElectrical System of the Heart
Purkinje fibers
Bundle of His
Sinoatrial node
Atrioventricular node
Pacemakers – Sinoatrial node, Atrioventricular node, Purkinje fibers

4. Pacemaker ActivityPacemaker Activity
• Spontaneous time-dependent depolarization
leading to action potentials
• Pacemaker with highest frequency sets the
heart rate.
– SA node – 60 beats/min – smallest electrical region in the
heart, sum of 3 ion channels produces pacemaker (ca, k, f)
– AV node – 40 beats/min – can take over for SA node,
pacemaker determined by same three channels as SA
node.
– Purkinje fibers –20 beats/min – unreliable pacemaker, but
great conducting system, pacemaker determined by ‘f’
channels only.

5. INa+
rapid
depolarizing
(non-nodal)
IK+
repolarizing
(all myocytes)
ICa+
depolarizing
(nodal AP
and myocyte
contraction)
If
“funny channel” or HCN
Pacemaker current
(activated during hyperpolarization)
Hyperpolarization activated Cyclic
Nucleotide gated channel
Na+
/K+
(activated during
depolarization)
MAJOR
MYOCYTE
ION CHANNELS
Which channel
is absent in SA and AV node?
Absent in ventricular myocytes?
Read-
Table 20-1

6. Pacemaker Action PotentialPacemaker Action Potential

7. Cardiac Muscle DepolarizationCardiac Muscle Depolarization

8. Ventricular Action PotentialVentricular Action Potential
5 Phases
0 – upstroke of AP
ICa+ – slow
ICa+/INa+ - fast
1 – rapid repolarization
Ik+ – activation
ICa+/INa+ - inactivation
2 – plateau phase
ICa+/INa+ - activated
3 – repolarization
Ik+
4 – diastolic potential
Ik+, ICa+, If
Produce pacemaker activity
SA/AV node, purkinje use If
Phase 1 and 2 not present in SA/AV nodePhase 1 and 2 not present in SA/AV node

9. Comparison of Slow Nodal andComparison of Slow Nodal and
Fast Non-nodal Cardiac Action PotentialsFast Non-nodal Cardiac Action Potentials

11. Velocity of Electrical ConductionVelocity of Electrical Conduction
Purkinje fibersPurkinje fibers
Bundle of HisBundle of His
(0.05 m/s)(0.05 m/s)
(0.05 m/s)(0.05 m/s)
(1.0-2.0 m/s)(1.0-2.0 m/s)
(1 m/s)(1 m/s)
(2.0-4.0 m/s)(2.0-4.0 m/s)
Functionally, how might the speeds be important?
(0.3-1.0 m/s)(0.3-1.0 m/s)
Ventricdular myocardiumVentricdular myocardium

12. Fletcher G F et al. Circulation 2001;104:1694-1740Copyright © American Heart Association
12 Lead ECG Electrode Placement12 Lead ECG Electrode Placement

13. Surface EKG MorphologySurface EKG Morphology

14. As the heart beats action
potentials on the heart cause an
electrical signal on the body
surface.
The larger the structure the
greater the voltage it induces.
This voltage pattern is called the
electrocardiogram

15. Atrial depolarization givesAtrial depolarization gives
rise to the P waverise to the P wave

16. Conduction throughConduction through
the small AV node isthe small AV node is
associated withassociated with
virtually no electricalvirtually no electrical
signal on the skin.signal on the skin.

17. Depolarization ofDepolarization of
the ventricle causesthe ventricle causes
the QRS complex.the QRS complex.
QRS is largeQRS is large
because thebecause the
ventricularventricular
mass is largemass is large
QRS is shortQRS is short
becausebecause
conduction overconduction over
the ventricles isthe ventricles is
very fastvery fast

18. Repolarization of the
ventricle causes the T
wave
Dispersion causes it to be
smaller and last longer than
the QRS complex.
Repolarization is not a
conducted wave.

19. Conduction/ Surface EKG MorphologyConduction/ Surface EKG Morphology

20. 12 Lead-12 Directions12 Lead-12 Directions
Help to Analyze Gross Heart conductionHelp to Analyze Gross Heart conduction

21. Normal atrial depolarization

22. 12 Lead-12 Directions12 Lead-12 Directions
Help to Analyze Gross Heart conductionHelp to Analyze Gross Heart conduction

23. 12 Lead-12 Directions12 Lead-12 Directions
Transition of Precordial LeadsTransition of Precordial Leads

25. 12 Lead-12 Directions12 Lead-12 Directions
Help to Analyze Gross Heart conductionHelp to Analyze Gross Heart conduction

27. Accessory PathwaysAccessory Pathways

28. Different Morpholgy indicatesDifferent Morpholgy indicates
different location-Atrial Tachycardiadifferent location-Atrial Tachycardia

29. 12 Lead-12 Directions12 Lead-12 Directions
Help to Analyze Gross Heart conductionHelp to Analyze Gross Heart conduction

31. Limb Leads
• 1. R1 + SIII > 25 mm
• 2. R wave in aVL > 11 mm
• 3. R wave in aVF > 20 mm
• 4. S wave in aVR > 14 mm
Precordial Leads
• 5. R wave in V5 or V6 > 26 mm
• 6. R wave in V5 or V6 + S wave in V1 > 35 mm
• 7. Largest R wave + largest S wave in the
precodial leads > 45 min
Voltage Indicates Ventricular MassVoltage Indicates Ventricular Mass
-Left Ventricular Hypertrophy-Left Ventricular Hypertrophy

32. 12 Lead-12 Directions12 Lead-12 Directions
Help to Analyze Gross Heart conductionHelp to Analyze Gross Heart conduction

33. Left Ventricular HypertrophyLeft Ventricular Hypertrophy

34. Intracardiac MappingIntracardiac Mapping

35. HRAHRA
HisHis
RVRV
CSCS

36. Example-Atrial TachycardiaExample-Atrial Tachycardia

37. Intracardiac MappingIntracardiac Mapping
Voltage imply the tissue electricalVoltage imply the tissue electrical
function or viabilityfunction or viability

38. Aging Changes of Typical AFL
Huang JL, Heart rhythm 2008

39. Intracardiac MappingIntracardiac Mapping
The timing of signal indicate the activation timeThe timing of signal indicate the activation time

40. Isochronal Map (Activation map)Isochronal Map (Activation map)

41. Distribution of AF triggerDistribution of AF trigger
Haissagurre et al. NEJM 1998Haissagurre et al. NEJM 1998 Chen et al. Circulation 1999Chen et al. Circulation 1999

42. Circumferential PV Isolation and SegmentalCircumferential PV Isolation and Segmental
AblationAblation

43. Thank you for your attention!Thank you for your attention!