Measurement of Pressures in Man by Cardiac Catheters

Relationships between artefacts in recorded intracardiac pulses and the dynamic response and susceptibility of catheter-manometer systems to artefacts caused by motion of the catheter were investigated. Sine-wave motions of the catheter, resembling motion frequently seen when the catheter is in the pulmonary artery, produce sine-wave pressure variations with peak-to-peak amplitudes of 10 mm. Hg. Square-wave motions (impacts) produce high-frequency pressure varia-tions, greatest (10 to 200 mm. Hg) when directed along the axis and much less when perpendicular to the axis of the catheter. High-fidelity records of pressure by conventional cardiac catheter-manometer systems are most unlikely when such catheters are threaded through the beating heart. THE recording of pressures from thechambers and vessels of the right sideof the heart in man usually must be done by means of a cardiac catheter connected to a manometer. For most purposes, the dy-namic response of such a system can quite easily be made adequate for sufficiently ac-curate reproduction of the pressure pulses in question.'- ' However, serious pressure arte-facts caused by impacts on and motion of the catheter imparted by the heart beat practically preclude high-fidelity recording of pressure pulses by this method if conventional catheter-manometer systems are used.2 ' 5 This study was carried out to obtain data concerning the optimal dynamic response characteristics of cardiac catheter-manometer systems for re-cording of pressure pulses by venous cathe-terization in man.* METHODS Pressure pulses and other physiologic variables were recorded during routine diagnostic cardiac eatheterization6 by a photo-oscillographic assembly-described elsewhere.7 In the majority of the studies, pressures were recorded via the catheter by means of a specially adapted strain-gauge manometer.6 Th