1. Pressure Measurement Grossman’s cardiac catheterization, angiography, and intervention CV R5 許志新醫師 Supervisor: 趙庭興醫師

2. Pressure Wave Complex periodic fluctuation in force per unit area

4. Pressure Measuring Devices

5. Sensitivity The ratio of the amplitude of the recorded signal to the amplitude of the input signal More rigid the sensing membrane,the lower the sensitivity

6. Frequency Response The ratio of output amplitude to input amplitude over a range of frequencies of the input pressure wave The range of good frequency response is improved by stiffening the membrane

8. Natural Frequency and Damping Any means of dissipating the energy of this oscillation, such as friction, is called damping. Optimal damping dissipates the energy gradually, thereby maintaining the frequency response curve nearly flat. Damping helps to prevent over-shoot artifacts resulting from resonance of the system,but diminished frequency response

10. What Frequency Response is Desirable The useful frequency response range of commonly used pressure measurement system is usually less than 20 Hz The natural frequency is directly proportional to the lumen radius of the catheter system and inversely to the length of the catheter

11. The Electrical Gauge Pressure measurement systems today generally use electrical strain gauges and employ the principle of the Wheatstone bridge.

12. Practical Pressure Transducer System for the Catheterization Laboratory

13. Zero Level The zero level should be positional approximately 5 cm below the left sternal border at the fourth left intercostal space. Each case should measure AP diameter at the level of the angle of Louis

15. Physiologic Caracteristics of Pressure Waveforms Reflected waves Wedge pressure

16. Reflected Waves

18. Wedge Pressures A true wedge pressure can be measured only in the absence flow

19. Sources of Error and Artifact Deterioration in frequency response Catheter impact artifact systolic pressure amplification in the periphery Errors in zero level, balancing, or calibration

20. Deterioration in Frequency Response Air bubbles: excessive damping and lower the natural frequency

21. Catheter Whip Artifact Catheter whip artifacts may produce superimposed waves of ± 10mmHg

22. End-pressure Artifact Flowing blood has a kinetic energy Flow suddenly come to a halt, the kinetic energy is converted in part into pressure 2-10 mmHg

23. Catheter Impact Artifact Catheter impact artifact are common with pigtail catheter in the left ventricular chamber, where terminal pigtail may be hit by the mitral valve leaflets as they open in early diastole

24. Systolic Pressure Amplification in the Periphery

25. This phenomenon may mask and distort pressure gradients across the aortic valve or left ventricular outflow tract. Double-lumen pigtail Second catheter Carefully pullback

26. Errors on Zero Level,Balancing, or Calibration Tracking down an unexpected pressure gradient, flushing of the zero line is an important initial step. If the unexpected gradient persists, catheter attachments should be switched between the two involved manifolds