2.6 THE NONLINEAR COMPONENTS OF PULSE PRESSURE: NOVEL MARKERS FOR ARTERIAL STIFFENING WITH PROGNOSTIC SIGNIFICANCE

Abstract

Mean ambulatory pulse pressure (PP) is a potent predictor of cardiovascular and all-cause mortality. Objectives. Investigating prognostic significance of elastic and non-elastic PP components Methods. Using a generalized nonlinear pressure–volume relationship in arteries (Fig. 1), PP can be split into an elastic component (PPel) with constant (diastolic) arterial stiffness and a non-elastic component (PPnel) that reflects arterial stiffening during the systole. We determined PPnel, PPel and the ratio WIF=PPnel/PPel (‘Widening Factor’) from 24-hour ambulatory BP measurements (ABPM) using a model. Standardized hazard ratios (HR) were estimated with Cox proportional hazards regression adjusted to age, gender, body mass index, mean arterial pressure, heart period (HP), systolic- and heart rate-dipping and diabetes and medication status. Assuming an exponential P-V relationship, the model provides the expression WIF=[(K-1)/ln(K)]-1, where K=SD(SBP)/SD(DBP) (SD=standard deviation) and PPel=PP/(1+WIF) Results. ABPM records of 2,105 individuals followed for 5 years for all-cause mortality were analyzed (age 56 ± 16, 55% women, 60% on medication and 9% diabetes, 115 died). Predictive power was demonstrated for patients with slower-than-median pulse rate (HP>0.87 s, n = 78): Mean(95%CI) HR of PPnel and WIF were 1.46(1.13–1.90) and 1.64(1.16–2.33) (P ≤ 0.005), respectively, and 1.59(1.21–2.1) and 1.83(1.27–2.63) (P = 0.001) for its subpopulation of older-than-median-age (>58 y, n = 73). The corresponding HR for PP was 1.34(1.03–1.75) (P = 0.03) and 1.53(1.15–2.03) (P = 0.004), respectively. PPel did not display predictive power. Fig. 2 shows that WIF varied strongly with age Conclusion. The 24-hour non-elastic PP component and the Widening Factor, which reflects arterial stiffening during the systole, are novel predictors for mortality, especially in elderly patients with slower pulse.