Evaluation of gender differences in endothelium-independent dilation using peripheral arterial tonometry

Background: A change in peripheral arterial tonometry (PAT) in response to reactive hyperaemia is often used to provide a non-invasive measure of endothelium-dependent dilation (EDD). Reactive hyperaemia does not allow one to quantify endothelium-independent dilation (EID), which is part of overall vascular function. Although most research examining vascular function and cardiovascular disease has focused on EDD, there is evidence that cardiovascular risk factors may impair EID. Purpose: To examine the microvascular vasodilation response to nitroglycerin (NTG) in healthy adults using PAT. Methods: Microvascular responses to reactive hyperaemia and NTG were evaluated in 86 (41 female and 45 male) healthy subjects (age 37±5years). Beat-to-beat plethysmographic measurements of finger arterial pulse waves were recorded for 5min following reactive hyperaemia. After a 10-min rest period, sublingual NTG (0·4mg) was administered and PAT signal changes were measured for 10min. Peak reactive hyperaemic index (RHI) and peak NTG-mediated index (NMI) were determined in all subjects. Results: There were no significant gender differences in peak RHI (females: 2·07±0·56 versus males: 1·91±0·58, P=0·20). Mean peak NMI for all subjects was 2·78 (±1·49). Peak NMI was significantly greater in females than in males (3·11±1·59 versus 2·50±1·34, P=0·05). Time to peak NMI was not significantly different between genders (7min, 28s [±1min, 47s], versus 7min, 14s [±1min, 49s], P=0·58). Conclusion: In this population of healthy adults, peak NMI was significantly greater in females than in males. These findings suggest that gender differences exist in the microvascular vasodilation responses to NTG using PAT.