Left ventricular pressure tracings

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INVASIVE & NONINVASIVE PRESSURE TRACING OF LEFT VENTRICLE

PRESSURE TRACING OF LEFT VENTRICLE

ByGopal C Ghosh

History of cardiac catheterisationThe cardiac catheter was......the key in the lock-Andre Cournand (1956)Cardiac catheterization was first performed by Claude Bernard in 1844(horse)Stephen Hales as first to do cardiac catheterisation in animals(1711 on horse)

Mueller RL et al. Am Heart J 1995;129:146.

Cardiac catheterisation in human

Werner Theodor Otto Forssmann(August 1904 June 1979) First to do cardiac catheterisation in human heartRetrograde left heart catheterization was first reported by Zimmerman, Scott & Becker and Limon-Lason and Bouchard in 1950.Zimmerman HA, Scott RW, Becker ND. Catheterization of the left side of the heart in man. Circulation 1950;1:357.

Dynamic pressure monitoringDynamic blood pressure has been of interest to physiologists and physicians1732- Stephen Hales measured the blood pressure of a horse by using a vertical glass tube

Fluid-filled standard catheter system Proper equipments for high quality catheterisation recordingsCoronary angiography: smallest-bore catheters, 5F & even 4FComplex hemodynamic catheterization is optimally performed with larger-bore catheters that yield high-quality hemodynamic data. To obtain proper hemodynamic tracings, 6F or even 7F catheters may be required

Manifold system

Fluid-filled catheter is attached by means of a manifold to a small-volume-displacement strain gauge type pressure transducer

Wheatstone bridge

Pressure MeasurementTerminologyNatural frequencyFrequency at which fluid oscillates in a catheter when it is tappedFrequency of an input pressure wave at which the ratio of output/input amplitude of an undamaged system is maximal

Grossman W. Cardiac Catheterization, Angiography, and Intervention. 5th Edition. Baltimore: Williams and Wilkins, 1996.Shorter catheterLarger catheter lumenLighter fluid

Higher natural frequency

Damping

Dissipation of the energy of oscillation of a pressure management system, due to friction

Greater fluid viscositySmaller catheter radiusLess dense fluid

Greater damping

Damped natural frequencyFrequency oscillations in the catheter when friction losses are taken into account

Natural frequency = Damping System critically dampedNatural frequency < Damping OVERdampedNatural frequency > Damping UNDERdamped

Less damping greater artifactual recorded pressure overshoot above true pressure when pressure changes suddenlyMore damping less responsive to rapid alterations in pressure

Sensitivity

Ratio of amplitude of the recordedsignal to the amplitude of the inputsignal

Optimal damping can maintain frequency response flat (output/input ratio = 1) to 88% of the natural frequency of the system

Frequency responseRatio of output amplitude to input amplitude over a range of frequencies of the input pressure waveFrequency response of a catheter system is dependent on catheters natural frequency and amount of dampingThe higher the natural frequency of the system, the more accurate the pressure measurement at lower physiologic frequencies

Grossman W. Cardiac Catheterization, Angiography, and Intervention. 7th Edition.

What is the optimal frequency response?The essential physiologic information is contained within the first 10 harmonics of the pressure wave's Fourier seriesThe useful frequency response range of commonly used pressure measurement systems is usually