Ambulatory arterial stiffness index: rationale and methodology

OBJECTIVES: Increased arterial stiffness is associated with the development of cardiovascular disease and may even predict its development at an early stage. Increased pulse pressure is seen as a marker of increased arterial stiffness and can be readily measured by ambulatory blood pressure monitoring. We propose another surrogate measure of arterial stiffness derived from ambulatory blood pressure monitoring that may predict cardiovascular mortality over and above pulse pressure, namely, the dynamic relationship between diastolic and systolic blood pressure over 24 h--the ambulatory arterial stiffness index. METHODS: Using all blood pressure readings over the 24-h period from 11 291 (5965 women; mean age 54.6 years) patients referred for ambulatory blood pressure monitoring to a blood pressure clinic, diastolic blood pressure was plotted against systolic blood pressure, and the regression slope was calculated; ambulatory arterial stiffness index was defined as one minus this regression slope. RESULTS: Both ambulatory arterial stiffness index and pulse pressure were higher in women (0.42 vs. 0.40 and 57.0 vs. 55.3 mmHg, respectively). For the entire group, the correlation between ambulatory arterial stiffness index and pulse pressure was 0.5. CONCLUSIONS: Ambulatory arterial stiffness index is a new measure that is readily available from ambulatory blood pressure monitoring and may provide added prognostic information for cardiovascular outcome.