The Heart: ECG Signal The Heart: ECG Signal

Basic structure of the heart

The simplified circulatory system. The blood is delivered from the right ventricle to the lung. The oxygenated blood from the lung is then returned to the left atrium before being sent throughout the body from the left ventricle. Deoxygenated blood from the body flows back to the right atrium and the cycle repeats.

The ECG initiates the cardiac cycle and cardiac sounds. The ejection occurs when the pressure in the left ventricle exceeds that in the arteries. Cardiac Cycle

Duration and characteristics of each major event in the cardiac cycle. EventCharacteristics Duration at 75 bpm (0.8 second cycle) Atrial systole Ventricular diastole AV valves opened. Semilunar valves close. Ventricular filling. 0.4 seconds Atrial systole Ventricular diastole AV valves open. Semilunar valves closed. Ventricular filling. 0.1 seconds Atrial diastole Ventricular systole AV valves closed. Semilunar valves open. Blood pumped into aorta and pulmonary artery. 0.3 seconds

A disposable surface electrode. A typical surface electrode used for ECG recording is made of Ag/AgCl.

Block diagram of an electrocardiograph.

VAVA VBVB VBVB A circuit of an ECG amplifier

Lead I is from RA to LA, lead II is from RA to LL, and lead III is from LA to LL. Einthoven’s triangle

(a)The normal ECG. (b)1st degree AV block in which the delay from the P wave to the Q wave is lengthened. (c)myocardial infarction (lack of blood flow to heart muscle, which causes tissue to die), in which the S–T segment is depressed. (a) (b) (c)

(d) right atrial hypertrophy (increase in muscle mass of the atria), in which V4 is large. (e) ventricular tachycardia with clear AV dissociation. (f) Wolff–Parkinson–White syndrome with atrial fibrillation. (d) (e) (f)

ECG Systems 12-lead ECG 12-lead ECG ECG Monitoring ECG Monitoring Ambulatory (Holter) Monitor Ambulatory (Holter) Monitor ECG Telemetry System ECG Telemetry System Exercise Stress Testing Exercise Stress Testing

The 1st and 2nd heart sounds are most prominent. SoundOrigin 1st sound Closure of mitral and tricuspid valves 2nd sound Closure of aortic and pulmonary valves 3rd sound Rapid ventricular filling in early diastole 4th sound Ventricular filling due to atrial contraction The heart sounds

Heart Sound Measurement Stethoscope Stethoscope Microphone Microphone

A stethoscope with bell and diaphragm modes.

R C vovo Electrode Microphone