Presence of a high-flow-mediated constriction phenomenon prior to flow-mediated dilation in normal weight, overweight, and obese children and adolescents

Total brachial artery reactivity and first time incident coronary heart disease events in a longitudinal cohort study: The multi-ethnic study of atherosclerosis

Background

Brachial artery reactivity (BAR) is usually determined as the maximum brachial artery diameter (BAD) following release of an occluding pressure cuff compared to a BAD before cuff inflation. BAD early after cuff deflation can also serve as baseline for estimating total brachial artery reactivity (TBAR). We investigate whether TBAR is associated with first time coronary heart disease events.

Methods

Participants of the Multi-Ethnic Study of Atherosclerosis (n = 5499) consisting of whites, African-Americans, Chinese and Hispanics were followed longitudinally for a mean of 12.5 years. Brachial artery ultrasound was performed following five minutes of cuff occlusion at the forearm. TBAR was estimated from BAD following cuff release as the difference between maximum and minimum brachial artery diameters divided by the minimum diameter multiplied by 100%. TBAR was added to multivariable Cox proportional hazards models with Framingham risk factors as predictors and time to first coronary heart disease event as outcome.

Results

Average TBAR was 9.7% (9.7 SD). Mean age was 61.7 years, 50.9% women. Increased TBAR was associated with lower risk of CHD events with a hazard rate of 0.78 per SD increase (95% C.I. 0.67, 0.91; p = 0.001). A TBAR below the median of 7.87% (Inter Quartile Range: 4.16%, 13.0%) was associated with a 31% lower risk of coronary heart disease event (Hazard Ratio: 0.69; 95% C.I.: 0.55, 0.87).

Conclusion

TBAR is an independent predictor of first time coronary heart disease events and is exclusively measured after release of a blood pressure occlusion cuff.

ULTRASONOGRAPHIC MARKERS OF CARDIOVASCULAR DISEASE RISK IN OBESE CHILDREN

Objective:

To evaluate whether the obesity alters ultrasonographical markers of metabolic and cardiovascular disease risk in children.

Methods:

A cross-sectional study evaluated 80 children aged between 6 and 10 years, comparing 40 obese with 40 normal children. The following parameters were assessed: weight; height; body mass index; arterial blood pressure; body fat; basal metabolic rate; HDL-cholesterol, LDL-cholesterol and total cholesterol; fasting insulin and glucose; quantitative insulin sensitivity check index (QUICKI); homeostasis model of assessment - insulin resistance (HOMA-IR); basal diameter of the brachial artery; brachial artery flow mediated dilation (FMD) and of pulsatility index change (PI-C).

Results:

Significant differences were observed between obese vs. non-obese children: systolic blood pressure (97.7±8.4 vs. 89.0±5.8 mmHg; p<0.01), diastolic blood pressure (64.3±7.9 vs. 52.9±5.1 mmHg; p<0.01), proportion of body fat (45.1±5.9 vs. 21.3±6.0%; p<0.01), basal metabolic rate (1216.1±102.1 vs. 1072.9±66.4 Kcal; p<0.01), total cholesterol (164.7±25.2 vs. 153.4±15.8 mg/dL; p=0.03), fasting insulin (7.1±5.2 vs. 2.8±1.8 pIU/mL; p<0.01), HOMA-IR (1.5±1.1 vs. 0.6±0.4; p<0.01), basal diameter of the brachial artery (2.5±0.3 vs. 2.1±0.3 mm; p<0.01); PI-C (-15.5±27.2 vs. -31.9±15.5%; p<0.01), decreased QUICKI (0.4±0.05 vs. 0.4±0.03; p<0.01), and FMD (6.6±3.2 vs. 15.6±7.3%; p<0.01).

Conclusions:

Obesity worsens ultrasonographical and laboratorial markers of metabolic and cardiovascular disease risk in children.

Intra- and inter-day reproducibility of low-flow mediated constriction response in young adults

PURPOSE

When assessing brachial endothelial function by reactive hyperaemia, stopping blood flow creates a period of low-flow-mediated constriction (L-FMC). As little is known about how this parameter influences flow-mediated vasodilation (FMD), the purpose of this study was to better understand this relationship and to determine the intra- and interday reproducibility of brachial L-FMC.

METHODS

Brachial L-FMC and FMD were measured on 26 healthy, young adults (13 males, 13 females; 24·6 ± 2·7 years). Each participant had two assessments conducted on two separate visits, separated by a minimum of seven days. Brachial artery baseline diameter was imaged during rest. Continuous imaging of the artery was performed during the last 20 s of cuff-occlusion to 180 s postcuff release. An L-FMC was considered present if the relative change from pre-occlusion baseline to L-FMC artery diameter was less than -0·1%.

RESULTS

Overall, there was a strong, positive correlation between increased brachial L-FMC and blunted FMD (visit 1 test 1: r = 0·758, P<0·001; visit 1 test 2: r = 0·706, P<0·001; visit 2 test 1: r = 0·836, P<0·001; visit 2 test 2: r = 0·857, P<0·001). The reproducibility of intra- and interday L-FMC diameter was intraclass correlation coefficients (ICC) = 0·627, coefficient of variation (CV) = 54·4% and ICC = 0·734, CV = 43·5%, respectively.

CONCLUSION

Vasoconstriction to low-flow conditions influences the subsequent maximal dilation during reactive hyperaemia. However, L-FMC is variable as evidenced by the weak intra- and interday reproducibility of the measure. Further research should study brachial L-FMC reproducibility among varying populations and the implications L-FMC has on the interpretation of FMD results.

Endothelial Function in Children and Adolescents Is Mainly Influenced by Age, Sex and Physical Activity - An Analysis of Reactive Hyperemic Peripheral Artery Tonometry

BACKGROUND

As adolescents rarely experience cardiovascular events, surrogate markers of atherosclerosis are useful to justify and monitor effects of primary prevention and therapy of risk factors. Endothelial function assessed by reactive hyperemic peripheral arterial tonometry (RH-PAT) resulting in a reactive hyperemic index (RHI) is a noninvasive method with limited data for use in children and adolescents.Methods and Results:We performed a total of 931 RHI measurements in 445 high-school students, aged 10-17 years, over a time period of 5 years. Students were randomized by class to 60 min physical exercise (PE) at school daily (intervention group), or 2 units of 45-min PE weekly (control group). To characterize the factors influencing the RHI, anthropometry, cardiopulmonary exercise testing, blood cholesterol and quality of life were assessed and used to build mixed linear models. Main influential factors were age, with an increase of RHI from 1.53±0.42 in the youngest to 1.96±0.59 in the oldest students, sex, with higher values in girls, and physical activity. This increase adjusted by age and sex was estimated as 0.11 [0.08, 0.14] per year. RHI was higher in the intervention group by 0.09 [-0.05, 0.23] in comparison with the control group.

CONCLUSIONS

If RH-PAT is used in research or as a clinical tool in adolescents, the shown age- and sex-dependence of RHI have to be taken in account.

High-flow-mediated constriction in adults is not influenced by biomarkers of cardiovascular and metabolic risk

PURPOSE

During reactive hyperemia, the brachial artery in some individuals constricts prior to dilation. Our aim was to describe the frequency of high-flow-mediated constriction (H-FMC) in adults, and its relationship to body composition and biomarkers of cardiovascular and metabolic risk.

METHODS

Two hundred forty-six adults (124 male, 122 female; 36 ± 7 years old) were assessed for H-FMC via sonographic imaging of the brachial artery. Blood pressure, glucose, insulin, lipids, and body composition assessed via dual energy X-ray absorptiometry were collected. H-FMC was characterized as a 10-second average of maximal postocclusion constriction. Independent t test was used to compare H-FMC versus non-H-FMC individuals.

RESULTS

H-FMC was observed in approximately 69% of adult participants (54 obese, 57 overweight, and 59 normal weight). Total body mass (82.3 ± 17.5 versus 76.3 ± 16.3 kg, p = 0.012), fat mass (27.7 ± 11.5 versus 23.8 ± 10.5 kg, p = 0.012), body mass index (27.7 ± 4.9 versus 26.1 ± 5.0 kg/m² , p = 0.018), and low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio (2.41 ± 1.03 versus 2.09 ± 0.72, p = 0.007) were higher in H-FMC than in non-H-FMC individuals. Flow-mediated dilatation (FMD) (6.12 ± 3.48 versus 8.09 ± 3.02%, p < 0.001) was lower in H-FMC subjects. However, there was no difference in brachial artery dilation between groups (7.57 ± 3.69 versus 8.09 ± 3.02%, p = 0.250) when H-FMC was added to FMD.

CONCLUSIONS

Increased body mass, fat mass, and body mass index were associated with a greater H-FMC. When H-FMC was present, the FMD response to reactive hyperemia was significantly lower. Because H-FMC has been observed to negatively affect FMD response to reactive hyperemia, we suggest that H-FMC should be noted when analyzing and interpreting FMD data. H-FMC may be an ancillary measure of endothelial health. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:35-42, 2017.