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Heart as a pump
• 250 - 300 g
• 70 - 75 beat/min, 5 l/min
• Automaticity (not driven by
motor nerve)
• Regulated by:
- autonomic nervous system
- metabolic demand
• (right) atrium:
- volume receptor
- endocrine organ (ANP)
Cardiac muscles
Cardiac tissues
dissociation
ultrastructure
Each cell has its own
electrical properties,
producing characteristic AP.
Multicellular tissue, but forms functional syncytium by
“ intercalated disk” (gap jt.-electrical synapse;
adherens jt and desmosome-mechanical coupling)
정상 상태: cytoplasmic resistance와 intercellular resistance가 비슷
하여 intercellular conduction (shaded)과 intracellular conduction
time이 비슷한 빠른 전도
Cardiac Function
Spontaneous Rhythm generation
Conduction
Contraction
Initiated and Regulated by Action Potentials
Electrical Activity에 관한 공부
1)
Generation and Conduction of Action Potential
2)
Generation of ECG:
- conduction of depolarization wave
- electrical heterogeneity of AP
3)
Ionic Basis of Action Potentials: How to understand the
generation of electrical signal (V) from the characteristics of ion
channels and currents (I): I vs V
4)
Abnormal electrical activity: Abnormal AP//Abnormal
conduction --- Arrhythmias
심장근 활동전압의 특징
Long Duration
Long Refractory Period
활동전압과 수축과의 관계 특징
골격근
심장근
tetanus
Long Refractory Period
No Tetanus
심장근과 골격근의 비교
Action Potential Duration
APD
Related with 1. Refractory period
2. Contractile force
Pacemaker and Specialized conduction system
Sino-Atrial Node
Atrial Track
AM
Atrio-Ventricular Node
His Bundle
Purkinje fibre
VM
AV conduction time
Regional difference of
cardiac action potentials and shape of myocytes
Phase of cardiac action potential
Depolarization
Phase 0
(upstroke)
Phase 1
Phase 2
Repolarization
Phase 3
Phase 4
(resting or diastolic)
Phase 4 0
1
2
3
Important Factors of Action Potential
1. Resting Membrane Potential
or Spontaneous Depolarization
2. Upstroke velocity (dV/dt)
3. Duration of AP (APD)
Phase 4
Resting Membrane Potential : VM, AM
Spontaneous Depolarization : SA, AV, PF
Dominent pacemaker/Latent pacemaker
Phase 0:
- Upstroke velocity is determined by the negativity of RMP
- Upstroke velocity determines the conduction velocity
Fast Action Potential : VM, AM, PF
Slow Action Potential : SA, AV
Electrocardiography (ECG, EKG)
A typical electrocardiogram:
important deflections and intervals
Cardiac Action Potential과 ECG와의 관계
ECG: 각 파의 의미:
Cardiac Action Potential과의 관계
QRS complex:
ventricular depol.
P wave:
atrial depolarization
PR interval:
AV conduction time
T wave:
ventricular repol.
QT interval:
AP duration
세포내 기록과 세포외 기록과의 관계
기록전극으로 다가오는
depolarization
positive deflection
기록전극으로 다가오는
repolarization
negative deflection
V2
(reference electrode
위치의 AP)
V1
(active electrode
위치의 AP)
Vextra=
−(V1-V2)
기록전극으로 다가오는
depolarization
기록전극으로 다가오는
repolarization
기록전극에서 멀어지는
repolarization
positive deflection
negative deflection
positive deflection
ECG is an
electrical “view” of three
dimensional structure
Use multiple leads
- Limb lead : standard
augmented
- Precordial lead : V1 - V6
Standard Limb Lead
Einthoven’s triangle
Limb Lead :
- bipolar: standard limb lead - I, II, III
- unipolar: augmented limb lead - aVR, aVL, aVF
심장을 frontal plane에서 봄
저분극과 재분극이
일어나는 순서
각 시점에서의
vector 방향
각 시점에서의
EKG
T-wave의 해석
(Bayliss & Starling, 1892)
개구리 심장의
기저부 가온
a: 정상
b: 기저부 가온
(Burdon-Sanderson & Page, 1883)
개구리 심장의
심첨부 가온
a: 정상
b,c: 심첨부 가온
d: 회복
(Mines, 1913)
Precordial Lead (unipolar)
심장을 transverse plane에서 봄
Electrical heterogeneity within the ventricular wall
APD
Epicardial
cell
shortest in Epi
M cell
longest in M cell
Endocardial
cell
J-wave
M-Epi
corresponds to ECG
Prominent notch in Epi
corresponds to J-wave
ECG reading
기록조건: y-axis: 10 mm /1 mV
x-axis: 25 mm /1 s
Reading:
1. Rate: normal/tachycardia/bradycardia
2. Rhythm: normal/arrhythmia
3. P wave <0.1 s, <2.5 mm
4. P-R interval <0.2 s
5. QRS complex <0.09 s, <35 mm
6. ST segment: isoelectric/elevation/
depression
7. T-wave: normal/ inversion
8. QT interval
9. Mean electrical axis, Transitional zone
Prolongation of APD produces Long QT
Mean Electrical Axis
Normal axis:
Right axis deviation
Left axis deviation
V5, V6로 이동
Clockwise rotation
Transitional zone:
정상에서 V3, V4
V1, V2로 이동:
Counterclockwise rotation
ECG
Einthoven, 1903, Human ECG
ECG Imaging
Nature Medicine, 2004
ECGI: ElectroCardioGraphic Imaging
to study normal activation and repolarization in unanesthetized
healthy adults under complete physiological conditions.
Epicardial Potentials
Isochrones
Activation sequence: earliest right ventricular (RV) epicardial breakthrough in the anterior
paraseptal region, subsequent RV and left ventricular (LV) breakthroughs, apex-to-base
activation of posterior LV, and late activation of LV base or RV outflow tract.
Repolarization sequence: determined by local repolarization properties (APD) rather than
by the activation sequence, significant dispersion of repolarization observed between RV
and LV and from apex to base.
Mean activation recovery interval (ARI): reflecting local APD, in the typical human APD
range (235 ms). Mean LV apex-to-base ARI dispersion was 42 ms. Average LV ARI
exceeded RV ARI by 32 ms.
PNAS, 103:6309–6314, 2006