Lesson 1, 2ELECTROCARDIOGRAPHY

2010. 05. 27 Ji-Won Kim

Main function of the heart

Pulmonary circuit To oxygenate the blood To remove carbon dioxide

Systemic circuit To deliver oxygen to tissues To deliver nutrients to tissues

동영상

Three types of cells for heart beat

Rhythm generators (SA node: pacemaker)

Conductors

Contractile cells (myo-cardium)

심장세포의 전기적 활동

심장세포내에는 많은 이온 (Na+, K+, Ca+, Cl-) 이 세포내외를 이동하면서 전기적 활동

분극 (Polarization) : 흥분하지 않은 휴식상태 . 안정기 탈분극 (Depolarization) : 세포의 흥분 후 일어나는 변화 재분극 (Repolarization) : 다시 안정기 . 전기배열과 이온배열이 원

상태로 되돌아 옴

심장 탈분극의 전도 (Electro-conduction)

Modulation of Heart rate and strength of contraction

Sympathetic ( 교감 ) system Acts as an accelerator, speeding up and

increasing the contractile force of the heart

Para-sympathetic ( 부교감 ) system Acts as a brake, slowing down the heart

Electrocardiogram

P wave Result from atrial depolarization

QRS wave Result of ventricular depolarization

T wave Result from ventricular repolarization

Electrocardiogram

PR interval The time it takes for the impulse sent from the SA node

to travel to the ventricles

PR segment The time of AV nodal delay and transmission to the

ventricles

Experimental objectives

To become familiar with the electrocardiograph

Electrical events vs. mechanical events

To observe rate and rhythm changes Associated with body position and breathing

Lead

Spatial arrangement of two electrodes on the body

Electrode placement Positive and negative electrodes Defines recording direction of the lead

Lead axis (vector) Determined by the direction going from the

negative to positive electrode

ECG recorder Computes the voltage difference between the

positive and negative electrodes

표준사지유도 (Standard bipolar limb lead)

두 전극 사이의 전압의 차를 절대치로 기록하는 양극 유도방식 심장을 전방에서 종축 ( 종단면 ) 으로 바라보는 방향

Einthoven’s Triangle

Chest(Precordial) lead( 흉부유도 ) : Horzontal plane V1, V2, V3, V4, V5, V6

V1: right 4th intercostal spaceV2: left 4th intercostal spaceV3: halfway between V2 and V4V4: left 5th intercostal space, mid-clavicular lineV5: horizontal to V4, anterior axillary lineV6: horizontal to V5, mid-axillary line

Mean electrical axis (mean cardiac vector)

Experimental objectives

Record ECG from lead 1 and 3 Lying down, sitting up and breathing deeply

while sitting

Review the ECGs for lead 2

Direction of QRS complex vs. the direction of the lead axis

Estimate the mean electrical axis of the QRS complex