Influence of Age and Central Hypertension on the Form Factor Needed to Estimate Mean Aortic Pressure, and Its Implications for Pulse Pressure Amplification: A Secondary Data Analysis.

Background: Mean aortic pressure (MAP) plays a pivotal role in both cardiovascular dynamics and the noninvasive estimation of systolic aortic pressure. MAP can be estimated by adding a fraction of the pulse pressure (PP) to the diastolic aortic pressure, known as the form factor (FF=100×[MAP-diastolic aortic pressure]/PP). A 41.2% FF is recommended, yet this single value may not adequately account for age- and pressure-related changes in both pressure waveform and central-to-peripheral pulse pressure amplification (pulse pressure amplification=peripheral PP/central PP=central FF/peripheral FF).

Methods And Results: This secondary analysis included data extracted from 11 high-fidelity invasive pressure studies. Individual data on age, high-fidelity systolic aortic pressure, diastolic aortic pressure, and time-averaged MAP were reanalyzed to calculate FF values and assess the influence of age and central hypertension on FF. The pooled data included 320 adults, comprising our own database (n=139). Among them, 97 subjects were initially categorized as "normal," 82 with hypertension, and 141 with diverse cardiac conditions (median age, 48 years; MAP, 102 mm Hg). The FF value (mean, 44%) decreased with age (=0.29, <0.0001). A value of 50% was most appropriate for the youngest subjects, while FF tended toward 40% in older subjects. FF was lower in subjects with central hypertension (systolic aortic pressure/diastolic aortic pressure ≥130/90 mm Hg; n=169) compared with those without. In both groups, FF decreased with age, showing similar slopes for the FF-age relationship.

Conclusions: Aortic FF decreased with age and was lower in subjects with central hypertension. Unlike applying a fixed FF, this decline aligned with pathophysiological changes in pressure waveform and pulse pressure amplification, with potential implications for improving MAP estimation.