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Medical Applications

Fractional Pulse Pressure (FPP)

Definition and Calculation

Fractional Pulse Pressure, also referred to as the Pulse Stress Ratio (PSR), is calculated as:

FPP = (Systolic − Diastolic) / Mean Arterial Pressure

where Mean Arterial Pressure (MAP) is approximated as:

MAP ≈ Diastolic + (Pulse Pressure * 0.412).

FPP therefore expresses the pulsatile component of arterial pressure as a proportion of the steady-state perfusion pressure, normalising for differences in average blood pressure between individuals.

Physiological Significance

Arterial stiffness is characterised by a disproportionate increase in the pulsatile component of blood pressure relative to mean pressure. In young adults with compliant vasculature, the Windkessel effect of large conduit arteries dampens the pressure wave generated by left ventricular ejection, limiting systolic excursion and maintaining a relatively narrow pulse pressure. With progressive arteriosclerosis, this buffering capacity diminishes: pulse wave velocity increases, reflected waves arrive during systole rather than diastole, and the PP widens relative to MAP. FPP captures this relationship directly.

Studies by Jankowski et al. demonstrated that fractional diastolic and systolic pressure indices derived from ascending aortic waveforms correlate independently with the extent of coronary artery disease, outperforming absolute pressure values in this regard. More accessible brachial measurements have also been shown to carry prognostic information: Li et al. (2020) reported in a cross-sectional study of stable angina patients that brachial PP was independently associated with the number of diseased coronary vessels after adjustment for age, sex, diabetes, and other conventional risk factors.

It is clinically important to contextualise FPP within the expected age-related trajectory: a value of 0.60 in a 72-year-old represents a physiologically normal finding, whereas the same value in a 38-year-old warrants further investigation.

Reference Ranges