Basic Cardiac Electrophysiology and ECG Concepts_20120902_北區

thrs 6,366 views 43 slides Sep 23, 2013

Slide 1 of 43

About This Presentation

No description available for this slideshow.

Size: 8.29 MB

Language: en

Added: Sep 23, 2013

Slides: 43 pages

Slide Content

Basic Cardiac Electrophysiology Basic 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

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

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

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.

I
Na+
rapid
depolarizing
(non-nodal)
I
K+
repolarizing
(all myocytes)
I
Ca+
depolarizing
(nodal AP
and myocyte
contraction)
I
f
“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

Pacemaker Action PotentialPacemaker Action Potential

Cardiac Muscle DepolarizationCardiac Muscle Depolarization

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

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

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

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

Surface EKG MorphologySurface EKG Morphology

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

Atrial depolarization gives Atrial depolarization gives
rise to the P wave rise to the P wave

Conduction through Conduction through
the small AV node is the small AV node is
associated with associated with
virtually no electrical virtually no electrical
signal on the skin.signal on the skin.

Depolarization of Depolarization of
the ventricle causes the ventricle causes
the QRS complex. the QRS complex.
QRS is large QRS is large
because the because the
ventricular ventricular
mass is largemass is large
QRS is short QRS is short
because because
conduction over conduction over
the ventricles is the ventricles is
very fast very fast

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.

Conduction/ Surface EKG MorphologyConduction/ Surface EKG Morphology