1. Chapter 8 Heart and Circulation

2. Figure 8.1 Basic structure of the heart. RA is the right atrium, RV is the right ventricle; LA is the left atrium, and LV is the left ventricle. Basic pacing rates are shown.

3. Figure 8.2 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.

4. Figure 8.3 In the top figure, the electrocardiogram (ECG) initiates the cardiac cycle. The cardiac sounds are also shown. The bottom figure shows that ejection occurs when the pressure in the left ventricle exceeds that in the arteries.

5. Table 8.1 Duration and characteristics of each major event in the cardiac cycle. EventCharacteristics Duration at 75 bpm (0.8 second cycle) Atrial diastole 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

6. Figure 8.4 A disposable surface electrode. A typical surface electrode used for ECG recording is made of Ag/AgCl. The electrodes are attached to the patients’ skin and can be easily removed.

7. Figure 8.5 The electrocardiogram. (a) The normal ECG. (b) 1st degree AV block in which the delay from the P wave to the Q wave is lengthened. (c) acute inferior myocardial infarction (lack of blood flow to heart muscle, which causes tissue to die), in which the S–T sement is depressed. (a) (b) (c)

8. Figure 8.5 The electrocardiogram. (d) right atrial hypertrophy (increase in muscle mass of the atria), in which V4 is large. (e) ventricular tachycardia (faster than normal heart rate) with clear AV dissociation. (f) Wolff–Parkinson–White syndrome with atrial fibrillation. (d) (e) (f)

9. Figure 8.6 Block diagram of an electrocardiograph. The normal locations for surface electrodes are right arm (RA), right leg (RL), left arm (LA), and left leg (LL). Physicians usually attach several electrodes on the chest of the patients as well.

10. Figure 8.7 A circuit of an ECG amplifier. The instrumentation amplifier, located on the left of the circuit provides a high input impedance and has a gain of 25 in the dc-coupled stages. (From Webster, J. G. (ed.) Medical Instrumentation: Application and Design. 3rd ed. Copyright © 1998 by John Wiley & Sons. Reprinted by permission of John Wiley & Sons.)

11. Figure 8.8 Einthoven’s triangle. Lead I is from RA to LA, lead II is from RA to LL, and lead III is from LA to LL.

12. Figure 8.9. A system for cardiac pressure and flow measurement. The pressure is usually measured with a catheter placed in the right side of the heart. An external strain gage pressure sensor is also shown. (Adapted from Orth, J. L. 1995. System for calculating compliance and cardiac hemodynamic parameters, US Patent, 5,423,323.)

13. Table 8.2 Some physiological variables. The data presented in this table are the average values of a group of subjects. Variables Mean (  SD) Weight (kg) 70 Cardiac output (mL/s) 110 Heart rate (min–1) 76 Mean velocity, ascending aorta (mm/s) 16 LV end-diastolic volume (mL) 125 (  31) LV end-systolic volume (mL) 42 (  17) LV stroke volume (mL) 82 (  20) LV ejection fraction 0.67 (  0.11) LV mean wall thickness (mm) 10.9 (  2.0) Cardiac output (CO) = heart rate (HR)  stroke volume (SV)

14. Figure 8.10 The relationship of the temperature gradient and time. Adapted from Baker, P. D., Orr, J., Westenskow, D. R. and Johnson, R. W. Method and apparatus for producing thermodilution cardiac output measurements utilizing a neural network, US Patent, 5,579,778.  T b = temperature gradient function c b = specific heat of the blood in J/(kg  K)  b = density of the blood in kg/m 3 Q = heat injected in joules

15. Figure 8.11 Simultaneous recording of motion mode (M-mode) and two dimensional echocardiograms. The arrows on the right image indicates the position of the ultrasound beam from which the M-mode recording was made. LVW = left ventricular wall, LV = left ventricle, LA = left atrium, RV = right ventricle. (From College of Veterinary Medicine, Univ. of Tennessee. 2003. M-Mode Echocardiography [Online] www.vet.utk.edu/)

16. Figure 8.12 2-D echocardiography of the long axis view of the right ventricle (RV): (a) the ultrasonic beam angle through the heart, (b) the cross-sectional diagram of the image and (c) the actual 2-D image. TV = tricuspid valve, AML = anterior mitral leaflet. (Adapted from Rafferty, T. 1992. Transesophageal two-dimensional echocardiography: www.gasnet.org/echomanual/html/2-d_echo.html). (a) (b) (c)

17. Table 8.2a Relative advantages of echocardiographic examination techniques. (Adapted from Roelandt, 1983) M-mode echocardiography Two-dimensional echocardiography Excellent time resolution Anatomical relationships Accurate dimensional measurements Shape information Timing of events against other parameters Lateral vectors of motion Easy storage and retrieval Easier to understand

18. Table 8.3 The heart sounds. 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

19. Table 8.4 Timing of murmurs. For example, if the physician hears the 1st heart sound, a swishing sound, and then the 2nd heart sound, the patient likely suffers from AV valve insufficiency. Characteristic Type of murmur Valve disorder Systolic murmur 1st HS  murmur  2nd HS 1st HS  murmur  2nd HSWhistlingSwishing Stenotic semilunar valve Insufficient AV valve Diastolic murmur 2nd HS  murmur  1st HS 2nd HS  murmur  1st HSWhistlingSwishing Stenotic AV valve Insufficient semilunar valve

20. Figure 8.13 A stethoscope with bell and diaphragm modes. ( Adapted from Mohrin, C. M., 1995. Stethoscope. US Patent, 5,389,747. )

21. Figure 8.14 The piezoelectric sensor generates charge, which is transferred to the capacitor, C, by the charge amplifier. Feedback resistor R causes the capacitor voltage to decay to zero.

22. xixi Deflection vovo v o max v o max /e Time Figure 8.15 The charge amplifier responds to a step input with an output that decays to zero with a time constant  = RC.

23. Figure 8.16 Principle of an electromagnetic flowmeter. e = Blu

24. Figure 8.17 Ultrasonic flowmeter. The sensor at the scan head transmits the signal from the oscillator and receives the reflected wave from the blood cells. The RF (radio frequency) amplifier amplifies the received signal and the carrier frequency, then AF (audio frequency) signal is produced by a detector. ( Adapted from Picot, P. A. and Fenster, A. 1996. Ultrasonic blood volume flow rate meter. US Patent, 5,505,204. )

25. Figure 8.18 Laser-Doppler flowmetry. Light that intercepts the red blood cells experiences a Doppler frequency shift.

26. Pressure/mmHg Figure 8.19 The sphygmomanometer detects arterial opening and closing that occurs between systolic and diastolic pressures.

27. Figure 8.20 The pressure of the cuff occludes the blood vessel. When the arterial pressure is greater than the pressure applied by the cuff, Korotkoff sounds are created and blood pressure can be measured.

28. Figure 8.21 Top: Cuff pressure with superimposed Korotkoff sounds, which appear between systolic and diastolic pressures. Bottom: the oscillometric method detects when the amplified cuff pressure pulsations exceed about 30% of maximal pulsations. (From Geddes, L. A. 1984. Cardiovascular devices and their applications. Copyright © by John Wiley & Sons. Reprinted by permission of John Wiley & Sons.)

29. Figure 8.22 A catheter is inserted through the blood vessels. A rotating ultrasonic transducer is attached at its tip and illuminates the walls.