Intravascular and Intracardiac Pressure Measurement

Abstract

Intravascular pressure measurement is one of the oldest techniques employed in clinical medicine. By 1733, long before accurate external blood pressure measurement had been developed by Korotkoff, Stephen Hales had performed direct measurement of arterial blood pressure by inserting a brass tube into a horse’s artery and observing the height of the resulting blood column. By 1828, Poiseuille had improved on intraarterial blood pressure measurement by using a fluid-filled catheter connected to a mercury manometer. In 1848 Ludwig invented the kymograph, a smoke-covered rotating cylinder that provided the means for graphical recording of dynamic signals for many years to come. By connecting the kymograph to a fluid-filled intraarterial catheter, the first graphical representation of the arterial pulse waveform was obtained.¹ Today, intravascular pressure measurement is performed so routinely in intensive care units, operating rooms and catheterization laboratories, that it is easy to forget that numbers and graphical representations of pressure are strongly affected by the measurement system, and indeed, can misrepresent reality. The signal processing techniques commonly used in intravascular and intraventricular pressure measurement are generally quite rudimentary and limited to simple filtering (see Chap. 4), averaging, and peak and trough detection. Less well-appreciated, but equally important, are the alterations in the raw signal introduced by the measurement system itself. In some cases, these artifacts can lead to serious errors in diagnosis. This chapter will provide an overview of how both intended and unintended signal processing affect the appearance and interpretation of data obtained using this nearly universal technique.