ASSOCIATION BETWEEN NON-INVASIVELY ASSESSED MACROVASCULAR REACTIVITY AND CARDIORESPIRATORY FITNESS IN A POPULATION AT RISK FOR CARDIOVASCULAR DISEASE.

Objective: Flow mediated slowing (FMS) enables non-invasive assessment of macrovascular reactivity by measuring the decline in brachial-radial pulse wave velocity (PWV) during reactive hyperaemia in a user-friendly way. However, its relationship with key cardiovascular (CV) risk factors remains underexplored. To further unravel the clinical value of FMS for CV risk stratification we assessed its association with peak oxygen uptake (VO2peak), a measure of cardiorespiratory fitness (CRF) and a key predictor for CV health. Design and method: FMS was measured in 152 subjects with at least one CV risk factor (obesity, diabetes, or hypertension) using the Vicorder® (80 Beats Medical, Berlin, Germany). For this, brachial-radial PWV was monitored at baseline and for 4 minutes during reactive hyperaemia after 5 minutes of cuff occlusion. FMS was analysed as relative PWV changes at 30-second intervals, as abnormal peak FMS based on validated reference cutoffs and as abnormal FMS response based on integrative trajectory analysis. VO2peak metrics were derived from a maximal cardiopulmonary exercise test, including the percentage of predicted VO2peak accounting for age, sex, length and weight. Correlation and multivariable regression analyses were performed. Results: The cohort (45% women) had a mean age of 60.0 ± 11.39 years old. We observed correlations between FMS intervals and VO2peak, with stronger FMS response associated with higher VO2peak (Figure 1). These correlations were significant (p<0.05) for percentage-predicted VO2peak. In multivariable-adjusted models, higher VO2peak was independently associated with the FMS response within the 0-180 seconds post-occlusion interval (p<0.05 for all). Significantly higher percentage-predicted VO2peak (Wasserman: p=0.02, Gläser: p=0.01) was observed in the high FMS response group compared to the low response group, which was supported by multivariable-adjusted regression (Table 1). After full adjustment, a ± 9% lower percentage-predicted VO2peak was observed in those with abnormal FMS peak or low overall FMS response (p<0.05). Conclusions: Worse FMS within the 0-180 seconds interval, an abnormal low FMS peak and an abnormal low FMS response correlated with significantly lower CRF. These findings highlight FMS as a practical tool with potential clinical value in cardiovascular risk stratification.