Aging is Associated With an Earlier Arrival of Reflected Waves Without a Distal Shift in Reflection Sites

Abstract

Background Despite pronounced increases in central pulse wave velocity ( PWV ) with aging, reflected wave transit time ( RWTT ), traditionally defined as the timing of the inflection point ( T INF ) in the central pressure waveform, does not appreciably decrease, leading to the controversial proposition of a “distal‐shift” of reflection sites. T INF , however, is exceptionally prone to measurement error and is also affected by ejection pattern and not only by wave reflection. We assessed whether RWTT , assessed by advanced pressure‐flow analysis, demonstrates the expected decline with aging. Methods and Results We studied a sample of unselected adults without cardiovascular disease (n=48; median age 48 years) and a clinical population of older adults with suspected/established cardiovascular disease (n=164; 61 years). We measured central pressure and flow with carotid tonometry and phase‐contrast MRI , respectively. We assessed RWTT using wave‐separation analysis ( RWTT WSA ) and partially distributed tube‐load (TL) modeling ( RWTT TL ). Consistent with previous reports, T INF did not appreciably decrease with age despite pronounced increases in PWV in both populations. However, aging was associated with pronounced decreases in RWTT WSA (general population −15.0 ms/decade, P <0.001; clinical population −9.07 ms/decade, P =0.003) and RWTT TL (general −15.8 ms/decade, P <0.001; clinical −11.8 ms/decade, P <0.001). There was no evidence of an increased effective reflecting distance by either method. T INF was shown to reliably represent RWTT only under highly unrealistic assumptions about input impedance. Conclusions RWTT declines with age in parallel with increased PWV , with earlier effects of wave reflections and without a distal shift in reflecting sites. These findings have important implications for our understanding of the role of wave reflections with aging.