Quantitative assessment of peripheral arterial obstruction in Raynaud's phenomenon: development of a predictive model of obstructive arterial cross-sectional area and validation with a Doppler blood flow study.

The objective of this study was to develop a method for the analytical assessment of arterial obstruction in conditions of Raynaud's phenomenon capable of providing diagnostic criteria. Numerous attempts have been made to determine and quantify arterial obstruction in terms of Doppler ultrasound measurements of arterial blood velocity. Absent from these methods is a formulation that allows an assessment of arterial obstruction based on the obstructed area as derived from direct measurement. The authors used spectral analysis of velocity signals from a pulsed, range-gated Doppler ultrasonic instrument to make quantitative measurements of arterial blood flow velocity in hands of normal subjects and persons with Raynaud's phenomenon. They measured the peak and mean velocity during the cardiac cycle and the time integral of the velocity signal over the cardiac cycle. These measurements for two distinct hemodynamic states induced by temperature changes allowed them to calculate the fractional change in arterial cross-sectional area produced by the change in temperature through the application of a hydraulic model of digital arterial circulation. They found an equation expressing fractional obstructed area expressed as: dA/A = 2 (dD - taudv - vtau)/(D + vdtau), where D is the time integral of the velocity signal; tau is the blood flow interval, v is the blood velocity; and dD, dtau and dv are the differences in D, tau, and v at two different hemodynamic states produced by two different temperature states. Their findings suggest that over a temperature range of 35 degrees-25 degrees C, normal subjects experience 0.05/ degrees C reduction in cross-sectional area while Raynaud subjects experience a reduction of 5.8%/degrees C. The results, based on findings in 13 subjects, suggest that Doppler ultrasound can differentiate persons with Raynaud's phenomenon from normal subjects. Additionally, the hydraulic model appears to offer the potential of assessing relative stenotic area in other arterial obstructive diseases.