Changes of Reactive Hyperemia Index (RHI) in Hypertensive Patients

Abstract

Recent epidemiological evidences indicates a complex association of hypertension with vascular endothelial dysfunction which causes the development and progression of atherosclerosis leading to adverse cardiovascular and cerebrovascular events due to reduction in nitric oxide (NO) bioavailability. The aim of the study was to investigate the value on reactive hyperemia peripheral arterial tonometry (RH-PAT) as a noninvasive tool to assess and compare endothelial function in between hypertensive and normotensives. Although they do not measure vascular function in the coronary circulation directly, they have been shown to correlate reasonably with its more invasive counterparts. A total of 73 hypertensive patients and 48 normotensive patients were consecutively recruited from Cardiology outpatient department of first affiliated hospital of Fujian medical university. Peripheral endothelial function was measured by using EndoPAT device to assess reactive hyperemia induced vasodilation and expressed by the reactive hyperemia index (RHI) with age, sex, BMI, height with the control subjects and further the relationship between RHI and clinical characteristics laboratory cardiovascular risk factors were also investigated. Statistical analysis were performed using SPSS software version 19.0. The normality of the distribution of variables were performed by the Kolmogorov-Smirnov test and homogeneity test of variance. Continuous variables were expressed as mean ± SD and categorical variables were expressed as percentages. Comparison between two normal groups were made by t-test, for abnormal distributed variables Mann-Whitney U test was used and χ2 test was performed for comparison of categorical variables. Pearson’s correlation analysis was used to assess associations between measured parameters and a p-value < 0.05 was considered to be statistically significant. RHI was significantly lower in hypertensive subjects compared to normotensive subjects (1.69 ± 0.46 vs 2.27 ± 0.60, p < 0.001) and when both groups were divided into different subgroups according to (sex, age < or ≥ 55, smoking, high cholesterol, physical activity, BMI, alcohol habit), significantly low RHI was noted in the hypertensive subgroups, p < 0.05. In the both groups there was no significant difference in normal cholesterol category where as in hypertensive group, subjects with regular physical activity had significantly high RHI as compared to those with no physical activity at all. In a univariate analysis age (r = -0.482, P = 0.001), Systolic BP (r = -0.312, P = 0.001), GFR (r = 0.196, P = 0.031), physical activity (r = 0.536, P = 0.001) were found to significantly correlate with RHI. In a multivariate analysis, only age (β = 0.004, P = 0.001) and SBP (β = 0.003, P = 0.010) significantly and independently correlated with RHI. RHI was significantly attenuated in hypertensive subjects and showed significant correlation between age, SBP, GFR, and physical activity indicating endothelial dysfunction, suggesting RH-PAT may be used as a non-invasive test to identify hypertensive patients with an early endothelial dysfunction.