Discovery of neurovascular reactivity in contralateral arm during a standard 5-minute arm-cuff reactive hyperemia - data from 7105 patient registry

Background Endothelial function testing using a 5-minute arm-cuff occlusion has always focused on hemodynamic measures from the occluded arm. We report the discovery of cutaneous vasodilatory and vasoconstrictive signals in the non-occluded arm. Methods Endothelial function tests were performed on 7105 patients using an FDA-approved automated VENDYS device during a 5-minute arm-cuff reactive hyperemia. Fingertip temperature in the occluded arm falls during occlusion and rebounds after release. Maximum temperature rebound in the occluded arm was reported as Vascular Reactivity Index (VRI). Temperature changes in the non-occluded arm were reported as the Neurovascular Reactivity Index (NVRI). Temperature oscillations in the non-occluded arm were reported as the Neurovascular Oscillation Index (NVOI). See infrared image as an example (Figure. 2). Results VRI was 1.54±0.47 in men and 1.62±0.56 in women (P<0.0001). NVRI was 0.71±1.65 in men and 0.50±1.83 in women (P<0.0001). Both VRI and NVRI showed a normal distribution. NVOI was 0.28±0.21 in men and 0.32±0.28 in women (P<0.0001). NVRI and NVOI showed positive and negative correlations with age respectively (P<0.0001). The top and bottom tertials of NVRI were classified as pro-parasympathetic and pro-sympathetic responders respectively. The top and bottom tertials of NVOI were classified as hyper and hypo-oscillators. Pro-sympathetic responders were younger, and hypo-oscillators were older than others. Conclusions We discovered significant and consistent contralateral neurovascular reactivity signals during ipsilateral arm-cuff endothelial function tests. The clinical utility of such vasodilatory or vasoconstrictive reactivity is unknown. Further basic and clinical investigations are warranted particularly in regard to neuronal vs. vascular nitric oxide-mediated response in the skin.