Influence of Aortic Pressure Wave Components Determined Noninvasively on Myocardial Oxygen Demand in Men and Women

Abstract

Myocardial oxygen consumption is increased by arterial stiffening. It is not known precisely how. This study aimed to evaluate the role of the incident and reflected pressure wave in raising myocardial oxygen demand. Central (aortic) pressure waveforms were generated from radial waveforms using a generalized transfer function in 1628 cardiology outpatients (1038 males and 590 females). Aortic waveforms were used to derive measures of incident and reflected waves, as well as to measure mean central systolic pressure (an indicator of systolic ventricular load), left ventricular ejection duration, and tension time index (a surrogate of myocardial oxygen demand) using validated techniques. Incident and reflected waves were measured using the conventional and an alternative method (aortic flow triangulation). Relationships were tested before and after correction for age, height, weight, heart rate, and mean arterial pressure using simple and multivariate linear regression models. Analyses were conducted separately by gender. In both genders (according to conventional or alternative methods of wave measurement), both the incident and reflected wave were strong predictors of tension time index (P<0.001). Both pressure waves raised the mean central systolic pressure (P<0.001). The reflected wave (P<0.001), unlike the incident wave (P>0.05), was also associated with a longer cardiac ejection duration. Tension time index (P<0.0001), mean central systolic pressure (P<0.001), and ejection duration (P<0.0001) were greater in women. Changes in arterial properties alter the nature of pressure wave propagation and predispose to cardiac ischemia (especially in women).