1. The Heart

2. Location of Heart Surrounded by pericardium 1.5cm left from center Size of a fist 250-300g 흉골 ( 胸骨 ) iPad mini: 308g 심낭, 심막

3. Anatomy of the Heart 4 Chambers 4 Valves Aorta –Pulmonary artery Veins –Superior vena cava –Inferior vena cava Septum –Thicker than RV walls

4. Cardiac Muscles Myocardium –Striated like skeletal muscles –Divided into 4 groups Spirally oriented –2 groups outside of RV & LV –3 rd group around RV & LV Inside of 1 st & 2 nd group –4 th group around LV only –Lower resistance in muscle fiber direction

5. Cardiac Muscle Cells Myocytes Same activation like neurons –AP about 100mV –But, longer duration  300ms –Plateau phase

6. Contraction Propagation of AP –From cell to cell In any direction –Rather complex waveform –Contraction within plateau Conduction barrier –Btw atria & ventricles –Conduction only through conduction pathway frog sartorius muscle cell frog cardiac muscle cell rat uterus wall smooth muscle cell

7. Generation of Pulses SinoAtrial node on RA –Special muscle cells –Shape of crescent –15mm long, 5mm wide –Self excitatory –Pacemaker cells 70 pulses/min –Activation start to propagate throughout the atria rather slowly

8. Conduction to Ventricles AtrioVentricular node –Only conducting path –Btw atria and ventricles –Intrinsic frequency 50 pulses/min –Follow higher trigger frequency

9. Propagation from AV Node Bundle of His –Fast conduction –Common bundle –Separate into 2 bundle branches Right bundle branch Left bundle branch –Purkinje fibers Diverge to inner side of ventricles

10. Propagating Ventricle Walls Formation of activation wavefront –Propagation through ventricular mass –Cell to cell activation –From inner to outer side Shorter AP impulse in epicardium(outside) –Earlier repolarization than endocardium(inside)

11. Electric Events in Heart Location in the heart EventTime [ms] ECG- wave Conduction velocity [m/s] Intrinsic frequency [1/min] SA node Atrium, Right Left AV node Bundle of His Bundle branches Purkinje fibers Endocardium Septum Left ventricle Epicardium Left ventricle Right ventricle Endocardium Left ventricle impulse generated depolarization depolarization arrival of impulse departure of impulse activated activated activateddepolarizationdepolarization repolarization repolarization 0 5 85 50 125 130 145 150 175 190 225 250 400 600 P P P-Q interval QRS T 0.05 0.8-1.0 0.8-1.0 0.02-0.05 1.0-1.5 1.0-1.5 3.0-3.5 0.3 (axial) - 0.8 (transverse) 0.5 70-80 50 20-40

12. Electric Potential Waveforms Intracellular recording –Microelectrodes inside cardiac cells

13. Isochronic Ventricle Activation By experiment with human heart –Within 30 min post mortem –870 electrodes Initial phase –Radial propagation From inside to outside In terminal phase –Tangential propagation

14. Electrocardiogram: ECG Recording of electrical activity –Generated by electric activity of the heart –On the surface of thorax –Extracellular electric behavior Properties in cardiac cells –Propagation through low resistance gap junction Current freely into following cells –Very restrictive extracellular space 25% of total volume, r o  r i  0 –Linear core conductor model

15. Linear Core Conductor Model

16. Depolarization

17. Repolarization Different from depolarization –Not propagating activity –Repolarize after certain time after Approximate with propagating wavefront –On equal duration of action pulses –Slow recovery: 100ms Wide recovery interval Negative V ECG potential –Equivalent with potential by dipole pointing reverse direction

18. Dipole Orientation In the example: –Opposite during depolarization and repolarization –Different V ECG polarity during depolarization and repolarization In real situation –AP pulse durations are not same Actually shorter AP in epicardium than endocardium Earlier repolarization in epicardium Same direction of dipole during depolarization and repolarization –Same V ECG polarity during de/repolarization

19. Dipole Orientation In the example: In real situation depolarization repolarization