ABSTRACT
Physiological waveforms (or cardiovascular variables) recorded in the experimental or clinical cardiovascular laboratory are usually time-varying periodic functions, such as the electrocardiogram, ventricular volume, arterial diameter, blood pressure, and blood flow (mean ascending aortic blood flow is taken as cardiac output). Each variable has its own characteristic waveform, which changes relatively little from one beat to the next in a constant physiologic state and cardiac sinus rhythm. Various transducers are used to convert these physiologic events of force, motion, etc., to electrical signals that are amplified, monitored, recorded, processed, stored, and analyzed. Pressure waves measured in the periphery can be transferred to a central site where the morphology is different. A large amount of information can be obtained from simple inspection and analysis of the wave contour (Wiggers, 1928; Murgo et al., 1980a; O’Rourke, 1982a; O’Rourke, 1982b; Khir et al., 2001; Nichols and Edwards, 2001; Nichols and Singh, 2002; Soderstrom et al., 2002; Denardo et al., 2010) (see Chapters 10 and 30), but more specific quantified variables can be measured and computed. For example, the reduced rate of rise of aortic and left ventricular pressures in aortic stenosis and myocardial dysfunction can usually be recognized at a glance, but measurement of the actual derivative (dP/dt) is more informative than a qualitative description of the wave. Also, the change in shape of the central aortic pressure wave with changes in arterial stiffness and wave reflections is obvious from visual inspection, but the augmentation index is more informative (Nichols et al., 2008). Recording of cardiovascular variables at the time of experimentation or cardiac catheterization is, therefore, only a first step to be followed by quantitative analysis. The goal of the analysis is to put the observations in a numerical form for easy tabulation and understanding.
