Hemodynamic correlates of blood pressure across the adult age spectrum: noninvasive evaluation in the Framingham Heart Study

Abstract

Background: Systolic blood pressure and pulse pressure are substantially higher in older adults. The relative contributions of increased forward versus reflected pressure wave amplitude or earlier arrival of the reflected wave to elevated pulse pressure remain controversial.

Methods and results: We measured proximal aortic pressure and flow, forward pressure wave amplitude, global wave reflection, reflected wave timing, and pulse wave velocity noninvasively in 6417 (age range, 19 to 90 years; 53 women) Framingham Heart Study Third Generation and Offspring participants. Variation in forward wave amplitude paralleled pulse pressure throughout adulthood. In contrast, wave reflection and pulse pressure were divergent across adulthood: In younger participants, pulse pressure was lower and wave reflection was higher with advancing age, whereas in older participants, pulse pressure was higher and wave reflection was lower with age. Reflected wave timing differed modestly across age groups despite considerable differences in pulse wave velocity. Forward wave amplitude explained 80 (central) and 66 (peripheral) of the variance in pulse pressure in younger participants (<50 years) and 90 and 84 in the older participants (≥ 50 years; all P<0.0001). In a stepwise model that evaluated age-pulse pressure relations in the full sample, the late accelerated increases in central and peripheral pulse pressure were markedly attenuated when variation in forward wave amplitude was considered.

Conclusions: Higher pulse pressure at any age and higher pulse pressure with advancing age is associated predominantly with a larger forward pressure wave. The influence of wave reflection on age-related differences in pulse pressure was minor.

Figure 1

Key hemodynamic variables summarized by decades of age. A. Blood pressure components: brachial systolic (SBP), central systolic (cSBP), diastolic (DBP) and mean arterial (MAP) pressure. B. Peripheral pulse pressure (PP) and central augmentation index (AI). C. Characteristic impedance of the aorta computed in the time domain (ZcTD) and reflected wave transit time (RWTT). D. Carotid-femoral (CFPWV) and carotid-brachial (CBPWV) pulse wave velocities. The sample size per decade was 463 (<30), 1334 (30-39), 1521 (40-49), 1096 (50-59), 1103 (60-69), 689 (70-79) and 213 (≥80).

Figure 2

Pressure amplification and measures of wave reflection by decades of age. A. Brachial (PP) and central (cPP) pulse pressure. B. Systolic ejection period (SEP), reflected wave transit time (RWTT), overlap between reflected wave arrival and the systolic ejection period (RW/SEP) and the global reflection factor (RF). C. True and apparent amplification and augmentation index (AI).