Renal vasodilating capacity and endothelial function are impaired in patients with obstructive sleep apnea syndrome and no traditional cardiovascular risk factors

Adjunctive benefits of low-frequency transcutaneous electrical nerve stimulation for obesity frequent chronic conditions: a systematic review

Background

Obesity is widely recognized for its role in predisposing individuals to a spectrum of chronic health conditions. Emerging preliminary evidence points to the potential benefits of low-frequency transcutaneous electrical nerve stimulation (Lo-TENS) in enhancing various health outcomes among those with obesity and associated disorders.

Objective

This systematic review was designed to assess the effectiveness of Lo-TENS for managing obesity and its related chronic diseases.

Methods

For this systematic review, we included randomized controlled trials that evaluated the impact of Lo-TENS on individuals with obesity and its associated chronic diseases.

Results

Eight trials encompassing 671 participants and spanning three unique populations: essential hypertension (EH), type 2 diabetes mellitus (T2DM), and obesity were deemed eligible for inclusion in this review. Compared to baseline measurements, Lo-TENS demonstrated a tendency to positively affect blood pressure in individuals with EH and metabolic parameters in those with T2DM. Nonetheless, the efficacy of Lo-TENS in treating obesity is not yet clear when contrasted with a no-intervention control group. When compared with other intervention modalities, three of the trials reported less favorable results.

Conclusions

Although Lo-TENS did not consistently surpass other treatments or yield substantial improvements, it generally provided greater benefits than the majority of placebo controls. This suggests that Lo-TENS could potentially serve as a beneficial adjunctive therapy in the management of obesity and its associated conditions. However, given the limited number of trials assessed, the elevated risk of bias within these studies, and the scarce evidence currently available, it is too early to reach definitive conclusions. Caution should be exercised when interpreting the current findings. There is an imperative for further high-quality research to thoroughly investigate and substantiate the efficacy of Lo-TENS in relation to obesity and its related disorders.

Association between sleep duration and sleep quality with arterial stiffness: A systematic review and meta-analysis

BACKGROUND

Altered sleep parameters, such as duration and quality, play an important role in the pathogenesis and progression of cardiovascular diseases, as well as in all-cause morbidity and mortality. It has been suggested that the specific mechanisms underlying this association could be through the influence of sleep parameters on vascular markers, such as arterial stiffness (AS), although this remains unclear. Thus, in this meta-analysis, we aimed to assess the association between sleep duration and sleep quality with AS in adults.

METHODS

PubMed, Scopus, Web of Science and Cochrane Library databases were searched from inception to July 30, 2021. The DerSimonian and Laird method was used to compute pooled effect size estimates and their respective 95% confidence intervals (95% CIs) of the association of sleep duration and sleep quality with AS. The Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies from the United States National Institute of Health National Heart, Lung, and Blood Institute was used to assess the risk of bias.

RESULTS

Finally, 14 studies (8 cross-sectional studies and baseline data from 6 prospective longitudinal studies) involving 97,837 individuals between 18 and 92 years of age were included. Our results showed that increased sleep duration, as continuous values, does not influence AS (effect size [ES]: 0.00; 95% CIs: -0.15, 0.15) in the general population. However, when sleep duration was longer than 8 hours (ES: 0.21; 95% CIs: 0.06, 0.36), according to sleep categories, a significant increase in pulse wave velocity was shown. Poor sleep quality was associated with increased AS (ES: 0.13; 95% CIs: 0.04, 0.21) in the general population. The overall risk of bias for studies examining sleep duration was fair in 77.8% of the included studies and the overall risk of bias for studies examining sleep quality was fair in 55.6%.

CONCLUSIONS

Our findings showed that both long sleep duration and poor sleep quality were associated with AS in adults. These findings underscore the influence of sleep on vascular health markers, specifically AS, as a possible pathway to explain the increased cardiovascular morbidity and mortality associated with sleep disorders.

Assessment of Stiffness of Large to Small Arteries in Multistage Renal Disease Model: A Numerical Study

Arterial stiffness (AS), as assessed via pulse wave velocity (PWV), is a major biomarker for cardiovascular risk assessment in patients with chronic kidney disease (CKD). However, the mechanisms responsible for the changes in PWV in the presence of kidney disease are not yet fully elucidated. In the present study, we aimed to investigate the direct effects attributable to biomechanical changes in the arterial tree caused by staged renal removal, independent of any biochemical or compensatory effects. Particularly, we simulated arterial pressure and flow using a previously validated one-dimensional (1-D) model of the cardiovascular system with different kidney configurations: two kidneys (2KDN), one single kidney (1KDN), no kidneys (0KDN), and a transplanted kidney (TX) attached to the external iliac artery. We evaluated the respective variations in blood pressure (BP), as well as AS of large-, medium-, and small-sized arteries via carotid-femoral PWV (cfPWV), carotid-radial PWV (crPWV), and radial-digital PWV (rdPWV), respectively. Our results showed that BP was increased in 1KDN and 0KDN, and that systolic BP values were restored in the TX configuration. Furthermore, a rise was reported in all PWVs for all tested configurations. The relative difference in stiffness from 2KDN to 0KDN was higher in the case of crPWV (15%) in comparison with the increase observed for cfPWV (11%). In TX, we observed a restoration of the PWVs to values close to 1KDN. Globally, it was demonstrated that alterations of the outflow boundaries to the renal arteries with staged kidney removal led to changes in BP and central and peripheral PWV in line with previously reported clinical data. Our findings suggest that the PWV variations observed in clinical practice with different stages of kidney disease may be partially attributed to biomechanical alterations of the arterial tree and their effect on BP.

Is kidney a new organ target in patients with obstructive sleep apnea? Research priorities in a rapidly evolving field

The bidirectional relationship between sleep disordered breathing and chronic kidney disease (CKD) has recently gained a lot of interest. Several lines of evidence suggest the high prevalence of coexistent obstructive sleep apnea (OSA) in patients with CKD and end-stage renal disease (ESRD). In addition, OSA seems to result in loss of kidney function in some patients, especially in those with cardio-metabolic comorbidities. Treatment of CKD/ESRD and OSA can alter the natural history of each other; still better phenotyping with selection of appropriate treatment approaches is urgently needed. The aim of this narrative review is to provide an update of recent studies on epidemiological associations, pathophysiological interactions, and management of patients with OSA and CKD or ESRD.

Effects of obstructive sleep apnea on the thoracic aorta and the main pulmonary artery: assessment by CT

STUDY OBJECTIVES

The influence of obstructive sleep apnea (OSA) on thoracic aortic size is debated. We aimed to identify possible relations between sleep parameters and the sizes of the ascending aorta (AA), the descending thoracic aorta (DTA), and the main pulmonary artery (MPA) in patients with untreated OSA and in a subgroup of participants without comorbidities capable of affecting the size of great thoracic vessels.

METHODS

We retrospectively measured AA, DTA, and MPA sizes on the chest computed tomography scans of 60 patients with OSA who underwent sleep studies within 1 year before or after the computed tomography. Univariate and multivariate analyses were performed on all patient findings, while an additional univariate analysis was conducted on the data for 22 participants without comorbidities. The latter had been divided into subgroups depending on the sleep parameters, and comparisons were made between them.

RESULTS

The logarithm of the time of oxygen saturation below 90% (CT90) significantly predicted AA and MPA sizes in all patients with OSA (P < .05). Oxygen desaturation index and minimum oxygen saturation were moderately correlated with AA and DTA sizes in patients without comorbidities (P < .01). In this group, subjects with oxygen desaturation index > 30 or minimum oxygen saturation < 81% had greater AA and DTA dimensions (P < .05).

CONCLUSIONS

In patients with OSA, time of oxygen saturation < 90% influenced AA and MPA sizes. In those patients without comorbidities, oxygen desaturation index and minimum oxygen saturation were moderately correlated with both AA and DTA sizes. Participants without comorbidities with oxygen desaturation index > 30 or minimum oxygen saturation < 81% had greater AA and DTA dimensions.

The Effects of Dapagliflozin on Systemic and Renal Vascular Function Display an Epigenetic Signature

CONTEXT

Mechanisms mediating the cardiovascular and renal protection exerted by SGLT2 inhibitors are still partially unknown. We investigated whether dapagliflozin modulates systemic and renal vascular function and structure, and induces epigenetic modifications.

SUBJECTS AND METHODS

Forty hypertensive patients with type 2 diabetes were randomly assigned to 4-week treatment with dapagliflozin 10 mg or hydrochlorothiazide (HCT) 12.5 mg. Routine analyses; plasma renin activity; aldosterone, catecholamine, and 24-hour urinary electrolyte levels; flow-mediated dilation (FMD) of the brachial artery; carotid-femoral pulse-wave velocity (PWV); augmentation index; and resistive index and dynamic renal resistive index (DRIN) were measured at baseline and after treatment. Circulating miRNAs (miRs) related to heart failure (miR30e-5p, miR199a-3p), endothelial dysfunction (miR27b and miR200b), and renal function (miR130b-3p, miR21-5p) were assessed and related to the effects of treatments.

RESULTS

Dapagliflozin and HCT marginally lowered blood pressure. Fasting glucose was lowered, whereas 24-hour diuresis, glycosuria, and osmolar clearance were increased by dapagliflozin (P < 0.001 for all), without affecting sodium excretion and glomerular filtration rate. Magnesium levels significantly increased after dapagliflozin treatment (P = 0.02). Neither dapagliflozin nor HCT modified FMD or PWV. DRIN did not vary in the dapagliflozin group, whereas it increased in the HCT group (P = 0.047 for time by treatment interaction). Both treatments induced variations in the expression of some miRs; dapagliflozin, but not HCT, significantly up-regulated miR30e-5p and downregulated miR199a-3p.

CONCLUSION

A putative epigenetic regulation of the protecting cardiovascular effect exerted by SGLT2 inhibitors was found. Dapagliflozin might exert nephroprotection by preserving renal vasodilating capacity.

Chronic kidney disease in patients with obstructive sleep apnea. A narrative review

Prevalence of both chronic kidney disease (CKD) and obstructive sleep apnea (OSA) is continuously increasing. Moreover, the prevalence of OSA increases as kidney function declines and is higher among patients with end-stage renal disease (ESRD). In addition, OSA is recognized as a potential nontraditional risk factor for development and progression of CKD. Continuous positive airway pressure (CPAP) plays a pivotal role in the management of OSA, eliminating patients' symptoms and improving their quality of life. Recent studies suggested that CPAP treatment may have beneficial effects on kidney function among patients with OSA. This narrative review summarizes the existing knowledge on the association between CKD and OSA, with emphasis on the epidemiology, the pathophysiology of the development of CKD in OSA and vice versa, as well as the effect of CPAP on renal function.

Hemodynamic and autonomic effects of low-dose glyceryl trinitrate used to test endothelium-independent vasodilation of the brachial artery

Smooth muscle function is explored by sublingual glyceryl trinitrate (GTN) administration to compare with endothelium-dependent vasodilation of the brachial artery by flow-mediated-dilation (FMD). This study compared the hemodynamic and autonomic effects of the two most often used GTN dosages. In 80 essential hypertensive patients (HT) and 60 normotensive subjects (NT), FMD of the brachial artery and endothelium-independent response to sublingual GTN (25 μg and 400 μg) were evaluated by high-resolution ultrasound and automated image analysis. In 10 HT, muscle sympathetic nerve activity (MSNA) was also assessed by microneurography. HT showed significantly (p < .01) lower FMD (5.5 ± 3.3%) compared to NT (6.9 ± 2.2%). The response to GTN 25 μg tended to be lower (HT:7.2 ± 3.3%; NT:7.9 ± 2.9%; p = .06), whereas response to GTN 400 μg was similar (HT:14.3 ± 4.8%, NT:14.5 ± 4.7%, p = ns). Blood pressure (BP) reduction induced by GTN 400 μg (systolic-BP:-3.2 ± 7.7 mm Hg, diastolic-BP:-4.7 ± 5.0 mm Hg) was greater (p < .001) compared to GTN 25 μg (systolic-BP:-0.7 ± 5.8 mm Hg, diastolic-BP:-0.7 ± 4.4 mm Hg). Changes in heart rate were also greater (+5.6 ± 6.4 bpm versus -0.2 ± 5.4 bpm, p < .001). This behaviour was similar in either NT or HT. MSNA was significantly increased by GTN 400 μg (31 ± 7bursts/min to 41 ± 6bursts/min, p < .001) but not by 25 μg (33 ± 9bursts/min to 37 ± 11bursts/min, p = .19). In conclusion, the administration of low-dose GTN allows exploring endothelium-independent vasodilation in FMD protocols, inducing only modest hemodynamic and sympathetic responses.

Arterial stiffness alteration and obstructive sleep apnea in an elderly cohort free of cardiovascular event history: the PROOF cohort study

INTRODUCTION

Several studies suggest in middle-aged subjects a relationship between arterial stiffness, a cardiovascular risk marker, and moderate to severe obstructive sleep apnea (OSA). No extensive data are present in older subjects. This study explores this association in a sample of healthy older subjects suffering OSA.

METHODS

A total of 101 volunteers aged 75.3 ± 0.7 years were examined at the hospital sleep center. Each subject was assessed for medical history, body mass index and 24-h blood pressure measures, biological blood samples, and home polygraphy in 2002-2003 (P2) as well as in 2009-2010 (P4). Arterial stiffness was also assessed using carotid-femoral and carotid-radial pulse wave velocity (cfPWV and crPWV) during P4 examination.

RESULTS

The total group consisted of 59 women and 42 men with a mean apnea-hypopnea index (AHI) of 17.8 ± 12.1 and a mean oxygen desaturation index (ODI) of 9.8 ± 8.9. No-OSA (AHI < 15) represented 50% of the sample, and severe cases (AHI > 30) 17%. No significant differences had been founded between men and women for blood pressure, cfPWV, and crPWV. Considering the severity of the AHI, no significant differences between groups were present for PWV and blood pressure values. No difference for PWV was present for subjects with and without hypertension. No correlation was found between PWV value and AHI and ODI values at P2 or between P2 and P4 visits. cfPWV was higher in patients demonstrating incident hypertension during the follow-up.

CONCLUSIONS

In this sample of older subjects, PWV is not affected by AHI and ODI but was associated with incident hypertension. These results may suggest potential protective and adaptive mechanisms in older sleep apnea patients.

CLINICAL TRIAL REGISTRATIONS

NCT 00759304 and NCT 00766584 .

The acute effect of continuous positive airway pressure titration on blood pressure in awake overweight/obese patients with obstructive sleep apnoea

OBJECTIVES

Continuous positive airway pressure (CPAP) improves upper airway obstruction in patients with obstructive sleep apnoea (OSA), who often are overweight-obese. Although it is thought that CPAP improves long-term blood pressure control (BP), the impact of acute and short-term CPAP use on the cardiovascular system in obese patients has not been described in detail.

METHODS

Obese patients (body mass index, BMI > 25 kg/m²) with OSA were studied awake, supine during incremental CPAP titration (4-20 cmH₂O, +2 cmH₂O/3 mins). BP was measured continuously with a beat-to-beat BP monitor (Ohmeda 2300, Finapres Medical Systems, Amsterdam/NL), BP variability (BPV) was calculated as the standard deviation of BP at each CPAP level, the 95% confidence interval (95%CI) was calculated and changes in BP and BPV were reported.

RESULTS

15 patients (12 male, 48 ± 10) years, BMI 38.9 ± 5.8 kg/m²) were studied; the baseline BP was 131.0 ± 10.2/85.1 ± 9.1 mmHg. BP and BPV increased linearly with CPAP titration (systolic BP r = 0.960, p < .001; diastolic BP r = 0.961, p < .001; systolic BPV r = 0.662, p = .026; diastolic BPV r = 0.886, p < .001). The systolic BP increased by +17% (+23.15 (7.9, 38.4) mmHg; p = .011) and the diastolic BP by +23% (+18.27 (2.33, 34.21) mmHg; p = .009), when titrating CPAP to 20 cmH₂O. Systolic BPV increased by +96% (+5.10 (0.67, 9.53) mmHg; p < .001) and was maximal at 14 cmH₂O, and diastolic BPV by +97% (+3.02 (0.26, 5.78) mmHg; p < .001) at 16 cmH₂O.

CONCLUSION

Short-term incremental CPAP leads to significant increases in BP and BPV in obese patients with OSA while awake. Careful titration of pressures is required to minimise the risk of nocturnal awakenings while improving BP control.

Dapagliflozin acutely improves endothelial dysfunction, reduces aortic stiffness and renal resistive index in type 2 diabetic patients: a pilot study

Background

Sodium-glucose cotransporter-2 inhibitors reduce blood pressure (BP) and renal and cardiovascular events in patients with type 2 diabetes through not fully elucidated mechanisms. Aim of this study was to investigate whether dapagliflozin is able to acutely modify systemic and renal vascular function, as well as putative mechanisms.

Methods

Neuro-hormonal and vascular variables, together with 24 h diuresis, urinary sodium, glucose, isoprostanes and free-water clearance were assessed before and after a 2-day treatment with dapagliflozin 10 mg QD in sixteen type 2 diabetic patients; data were compared with those obtained in ten patients treated with hydrochlorothiazide 12.5 mg QD. Brachial artery endothelium-dependent and independent vasodilation (by flow-mediated dilation) and pulse wave velocity were assessed. Renal resistive index was obtained at rest and after glyceryl trinitrate administration. Differences were analysed by repeated measures ANOVA, considering treatment as between factor and time as within factor; Bonferroni post hoc comparison test was also used.

Results

Dapagliflozin decreased systolic BP and induced an increase in 24 h diuresis to a similar extent of hydrochlorothiazide; 24 h urinary glucose and serum magnesium were also increased. 24 h urinary sodium and fasting blood glucose were unchanged. Oxidative stress was reduced, as by a decline in urinary isoprostanes. Flow-mediated dilation was significantly increased (2.8 ± 2.2 to 4.0 ± 2.1%, p < 0.05), and pulse-wave-velocity was reduced (10.1 ± 1.6 to 8.9 ± 1.6 m/s, p < 0.05), even after correction for mean BP. Renal resistive index was reduced (0.62 ± 0.04 to 0.59 ± 0.05, p < 0.05). These vascular modifications were not observed in hydrochlorothiazide-treated individuals.

Conclusions

An acute treatment with dapagliflozin significantly improves systemic endothelial function, arterial stiffness and renal resistive index; this effect is independent of changes in BP and occurs in the presence of stable natriuresis, suggesting a fast, direct beneficial effect on the vasculature, possibly mediated by oxidative stress reduction.

The Role of the Autonomic Nervous System in the Pathophysiology of Obesity

Obesity is reaching epidemic proportions globally and represents a major cause of comorbidities, mostly related to cardiovascular disease. The autonomic nervous system (ANS) dysfunction has a two-way relationship with obesity. Indeed, alterations of the ANS might be involved in the pathogenesis of obesity, acting on different pathways. On the other hand, the excess weight induces ANS dysfunction, which may be involved in the haemodynamic and metabolic alterations that increase the cardiovascular risk of obese individuals, i.e., hypertension, insulin resistance and dyslipidemia. This article will review current evidence about the role of the ANS in short-term and long-term regulation of energy homeostasis. Furthermore, an increased sympathetic activity has been demonstrated in obese patients, particularly in the muscle vasculature and in the kidneys, possibily contributing to increased cardiovascular risk. Selective leptin resistance, obstructive sleep apnea syndrome, hyperinsulinemia and low ghrelin levels are possible mechanisms underlying sympathetic activation in obesity. Weight loss is able to reverse metabolic and autonomic alterations associated with obesity. Given the crucial role of autonomic dysfunction in the pathophysiology of obesity and its cardiovascular complications, vagal nerve modulation and sympathetic inhibition may serve as therapeutic targets in this condition.

Genome-wide gene expression array identifies novel genes related to disease severity and excessive daytime sleepiness in patients with obstructive sleep apnea

We aimed to identify novel molecular associations between chronic intermittent hypoxia with re-oxygenation and adverse consequences in obstructive sleep apnea (OSA). We analyzed gene expression profiles of peripheral blood mononuclear cells from 48 patients with sleep-disordered breathing stratified into four groups: primary snoring (PS), moderate to severe OSA (MSO), very severe OSA (VSO), and very severe OSA patients on long-term continuous positive airway pressure treatment (VSOC). Comparisons of the microarray gene expression data identified eight genes up-regulated with OSA and down-regulated with CPAP treatment, and five genes down-regulated with OSA and up-regulated with CPAP treatment. Protein expression levels of two genes related to endothelial tight junction (AMOT P130, and PLEKHH3), and three genes related to anti-or pro-apoptosis (BIRC3, ADAR1 P150, and LGALS3) were all increased in the VSO group, while AMOT P130 was further increased, and PLEKHH3, BIRC3, and ADAR1 P150 were all decreased in the VSOC group. Subgroup analyses revealed that AMOT P130 protein expression was increased in OSA patients with excessive daytime sleepiness, BIRC3 protein expression was decreased in OSA patients with hypertension, and LGALS3 protein expression was increased in OSA patients with chronic kidney disease. In vitro short-term intermittent hypoxia with re-oxygenation experiment showed immediate over-expression of ADAR1 P150. In conclusion, we identified a novel association between AMOT/PLEKHH3/BIRC3/ADAR1/LGALS3 over-expressions and high severity index in OSA patients. AMOT and GALIG may constitute an important determinant for the development of hypersomnia and kidney injury, respectively, while BIRC3 may play a protective role in the development of hypertension.

Olfactory evaluation in Mild Cognitive Impairment: correlation with neurocognitive performance and endothelial function

Mild Cognitive Impairment (MCI) is an intermediate condition between normal aging and dementia, associated with an increased risk of progression into the latter within months or years. Olfactory impairment, a well-known biomarker for neurodegeneration, might be present in the condition early, possibly representing a signal for future pathological onset. Our study aimed at evaluating olfactory function in MCI and healthy controls in relation to neurocognitive performance and endothelial function. A total of 85 individuals with MCI and 41 healthy controls, matched for age and gender, were recruited. Olfactory function was assessed by Sniffin' Sticks Extended Test (Burghart, Medizintechnik, GmbH, Wedel, Germany). A comprehensive neurocognitive assessment was performed. Endothelial function was assessed by flow-mediated dilation (FMD) of the brachial artery by ultrasound. MCI individuals showed an impaired olfactory function compared to controls. The overall olfactory score is able to predict MCI with a good sensitivity and specificity (70.3 and 77.4% respectively). In MCI, olfactory identification score is correlated with a number of neurocognitive abilities, including overall cognitive status, dementia rating, immediate and delayed memory, visuospatial ability and verbal fluency. FMD was reduced in MCI (2.90 ± 2.15 vs. 3.66 ± 1.96%, P = 0.016) and was positively associated with olfactory identification score (ρ_s =0.219, P = 0.025). The association remained significant after controlling for age, gender, and smoking. In conclusion, olfactory evaluation is able to discriminate between MCI and healthy individuals. Systemic vascular dysfunction might be involved, at least indirectly, in olfactory dysfunction in MCI.

Patients with Obstructive Sleep Apnea Display Decreased Flow-Mediated Dilatation: Evidence from a Meta-Analysis

Background

Endothelial dysfunction, which can be measured by flow-mediated dilatation (FMD), is an early clinical marker of atherosclerosis, which is considered to be the main cause of the observed cardiovascular complications in obstructive sleep apnea (OSA) patients. The association between OSA and endothelial dysfunction has been reported in a number of studies; however, the findings are not entirely consistent. Our aim was to meta-analytically synthesize the existing evidence to explore the association between OSA and endothelial dysfunction.

Material/Methods

Data from PubMed, EMBASE, the Cochrane library, and Google Scholar for all trials that investigated the relationship between endothelial dysfunction and OSA were systematically reviewed. The minimum inclusion criteria for the studies were reporting of the Apnea-Hypopnea Index (AHI) and FMD measurements (as an indicator of endothelial dysfunction) for both OSA and control groups. Data from case-control studies that met the inclusion criteria were extracted.

Results

Twenty-eight studies comprising a total of 1496 OSA patients and 1135 controls were included in the meta-analysis. A random-effects model was used. The weighted mean difference in the FMD measurements was −3.07 and the 95% confidence interval was −3.71 to −2.43 (P<0.01). Meta-regression analysis showed that age, sex, body mass index (BMI), blood pressure, glucose, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol did not explain the heterogeneity.

Conclusions

This meta-analysis showed that patients with OSA have decreased FMD, which may contribute to the development of atherosclerosis.

Impact of seasonality and air pollutants on carotid-femoral pulse wave velocity and wave reflection in hypertensive patients

Objective

The effects of seasonality on blood pressure (BP) and cardiovascular (CV) events are well established, while the influence of seasonality and other environmental factors on arterial stiffness and wave reflection has never been analyzed. This study evaluated whether seasonality (daily number of hours of light) and acute variations in outdoor temperature and air pollutants may affect carotid-femoral pulse wave velocity (PWV) and pressure augmentation.

Design and method

731 hypertensive patients (30–88 years, 417 treated) were enrolled in a cross-sectional study during a 5-year period. PWV, central BP, Augmentation Index (AIx) and Augmentation Pressure (AP) were measured in a temperature-controlled (22–24°C) room. Data of the local office of the National Climatic Data Observatory were used to estimate meteorological conditions and air pollutants (PM₁₀, O₃, CO, N₂O) exposure on the same day.

Results

PWV (mean value 8.5±1.8 m/s) was related to age (r = 0.467, p<0.001), body mass index (r = 0.132, p<0.001), central systolic (r = 0.414, p<0.001) and diastolic BP (r = 0.093, p = 0.013), daylight hours (r = -0.176, p<0.001), mean outdoor temperature (r = -0.082, p = 0.027), O₃ (r = -0.135, p<0.001), CO (r = 0.096, p = 0.012), N₂O (r = 0.087, p = 0.022). In multiple linear regression analysis, adjusted for confounders, PWV remained independently associated only with daylight hours (β = -0.170; 95% CI: -0.273 to -0.067, p = 0.001). No significant correlation was found between pressure augmentation and daylight hours, mean temperature or air pollutants. The relationship was stronger in untreated patients and women. Furthermore, a positive, independent association between O₃ levels and PWV emerged in untreated patients (β: 0.018; p = 0.029; CI: 0.002 to 0.034) and in women (β: 0.027; p = 0.004; CI: 0.009 to 0.045).

Conclusions

PWV showed a marked seasonality in hypertensive patients. Environmental O₃ levels may acutely reduce arterial stiffness in hypertensive women and in untreated patients.

Advances in the non-invasive assessment of vascular dysfunction in metabolic syndrome and diabetes: Focus on endothelium, carotid mechanics and renal vessels

AIM

The present paper is a selective review on the methodology and clinical significance of techniques to assess specifically endothelial function, carotid mechanics and renal vascular function, particularly in the light of vascular dysfunction in metabolic syndrome and type 2 diabetes.

DATA SYNTHESIS

Endothelial dysfunction appears to be earlier detectable in the microcirculation of patients with altered glucose metabolism, while it attains significance in the macrocirculation at more advanced disease stages. Smooth muscle cell dysfunction is now increasingly recognized to play a role both in the development of endothelial dysfunction and abnormal arterial distensibility. Furthermore, impaired glucose metabolism affects carotid mechanics through medial calcification, structural changes in extracellular matrix due to advanced glycation and modification of the collagen/elastin material stiffness. The assessment of renal vascular function by dynamic ultrasound or magnetic resonance imaging has recently emerged as an appealing target for identifying subtle vascular alterations responsible for the development of diabetic nephropathy.

CONCLUSIONS

Vascular dysfunction represents a major mechanism for the development of cardiovascular disease in patients with abnormal glucose metabolism. Hence, the currently available non-invasive techniques to assess early structural and vascular abnormalities merit recommendation in this population, although their predictive value and sensitivity to monitor treatment-induced changes have not yet been established and are still under investigation.

Serum of obstructive sleep apnea patients impairs human coronary endothelial cell migration

INTRODUCTION

Endothelial cell migration and proliferation play an important role in the growth and development of new blood vessels and endothelium healing. This process occurs in response to injury, inflammation and immune reactions. Dysfunction of the endothelium may play a significant role in development and progression of cardiovascular disease related to sleep-disordered breathing. The aim of our study was to evaluate the chemo-attractant activity of serum from obstructive sleep apnea (OSA) and normal subjects on coronary artery endothelial cell migration.

MATERIAL AND METHODS

We studied 12 severe OSA patients, free of other co-morbidities and on no treatment, along with 12 age-, body mass index, and gender matched healthy controls. Blood was collected at three time points: at 21:00 before sleep, at 6:00 after waking from sleep, and at 11:00 (after 5 h of normal daytime activity). Serum chemo-attractant activity for human coronary endothelial cells was assessed using a colorimetric cell migration assay kit.

RESULTS

In healthy subjects, serum chemo-attractant activity peaked in the morning after waking from sleep (p = 0.02). This early morning increase was blunted in severe OSA subjects, in whom chemo-attractant activity was weaker than in normal controls (p = 0.02), and did not change significantly at the different time-points (p < 0.001 vs. controls).

CONCLUSIONS

Chemo-attractant activity of the serum from OSA patients is lower compared to serum from healthy subjects, especially in the morning. Altered chemo-attractant serum activity may conceivably contribute to the impairment of endothelial function in obstructive sleep apnea patients.

Emerging co-morbidities of obstructive sleep apnea: cognition, kidney disease, and cancer

Obstructive sleep apnea (OSA) causes daytime fatigue and sleepiness, and has an established relationship with cardiovascular and metabolic disease. Recent years have seen the emergence of an evidence base linking OSA with an increased risk of degenerative neurological disease and associated cognitive impairment, an accelerated rate of decline in kidney function with an increased risk of clinically significant chronic kidney disease (CKD), and with a significantly higher rate of cancer incidence and death. This review evaluates the evidence base linking OSA with these seemingly unrelated co-morbidities, and explores potential mechanistic links underpinning their development in patients with OSA, including intermittent hypoxia (IH), sleep fragmentation, sympathetic excitation, and immune dysregulation.

An update on cardiovascular effects of obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome is an important health problem which may cause or worsen systemic diseases. Chronic intermittent hypoxia during repetitive airflow cessations may cause endothelial dysfunction. Sleep apnoea is also shown to be associated with hypercoagulability which may be due to decreased nitric oxide levels and impaired vasodilatation. Endothelial dysfunction, increased systemic inflammation, sympathetic nervous system activation, increased oxidative stress and dysglycaemia may all contribute to cardiovascular processes such as hypertension, arrhythmia, stroke, heart failure and coronary artery disease in patients with obstructive sleep apnoea. Treatment approaches in patients with obstructive sleep apnoea mainly focus on maintaining upper airway patency either with positive airway pressure devices or upper airway appliances. Strategies involving positive airway pressure therapy are associated with decreased morbidity and mortality. Obstructive sleep apnoea should be suspected as an underlying mechanism in patients with cardiovascular disease and warrants appropriate treatment.

Urinary Neutrophil Gelatinase-Associated Lipocalin (NGAL) in Patients with Obstructive Sleep Apnea

Background

Obstructive sleep apnea (OSA) is a well-established risk factor for hypertension and cardiovascular morbidity and mortality. More recently, OSA has been implicated as an independent risk factor for chronic kidney disease. Urinary neutrophil gelatinase-associated lipocalin (NGAL) is a well-accepted early biomarker of subclinical kidney tubular injury, preceding an increase in serum creatinine. The goal of this study was to determine if an association exists between OSA and increased urinary NGAL levels.

Methods

We prospectively enrolled adult patients from the sleep clinic of an academic medical center. Each underwent polysomnography and submitted a urine specimen upon enrollment. We measured NGAL and creatinine levels on all urine samples before participants received treatment with continuous positive airway pressure (CPAP), and, in a subset of OSA patients, after CPAP therapy. We compared the urinary NGAL/creatinine ratio between untreated participants with and without OSA, and within a subset of 11 OSA patients also after CPAP therapy.

Results

A total of 49 subjects were enrolled: 16 controls based on an apnea-hypopnea index (events with at least 4% oxygen desaturation; AHI-4%) <5 events/hour (mean AHI-4% = 0.59 +/- 0.60); 33 OSA patients based on an AHI-4% >5 events/hour (mean AHI-4% = 43.3 +/- 28.1). OSA patients had a higher mean body-mass index than the control group (36.58 +/- 11.02 kg/m² vs. 26.81 +/- 6.55 kg/m², respectively; p = 0.0005) and were more likely to be treated for hypertension (54.5% vs. 6.25% of group members, respectively; p = 0.0014). The groups were otherwise similar in demographics, and there was no difference in the number of diabetic subjects or in the mean serum creatinine concentration (control = 0.86 +/- 0.15 mg/dl, OSA = 0.87 +/- 0.19 mg/dl; p = 0.7956). We found no difference between the urinary NGAL-to-creatinine ratios among untreated OSA patients versus control subjects (median NGAL/creatinine = 6.34 ng/mg vs. 6.41 ng/mg, respectively; p = 0.4148). Furthermore, CPAP therapy did not affect the urinary NGAL-to-creatinine ratio (p = 0.7758 for two-tailed, paired t-test).

Conclusions

In this prospective case-control study comparing patients with severe, hypoxic OSA to control subjects, all with normal serum creatinine, we found no difference between urinary levels of NGAL. Furthermore, CPAP therapy did not change these levels pre- and post-treatment.

Cumulative Hypoxemia During Sleep Predicts Vascular Endothelial Dysfunction in Patients With Sleep-Disordered Breathing

BACKGROUND

Sleep-disordered breathing (SDB) is associated with repeated intermittent hypoxemia, and it is known as one of the risk factors for cardiovascular diseases. Previous studies assessing the effects of frequency and depth of hypoxemia on cardiovascular diseases have shown conflicting results. The aim of the current study was to clarify what SDB-related parameters most predict endothelial dysfunction to better understand the pathogenesis of endothelial dysfunction in patients with SDB.

METHODS

We conducted polysomnography (PSG) and measured flow-mediated vasodilation response (%FMD) in 50 outpatients suspected of SDB. Evaluated indices included: apnea-hypopnea index (AHI), 3% oxygen desaturation index (3%ODI), averaged arterial oxygen saturation (averaged SpO2), lowest arterial oxygen saturation (lowest SpO2), ratio of arterial oxygen saturation <90% (

RESULTS

Significant differences were observed only in the TDS between the first and third (P = 0.03) and between the first and forth (P = 0.04) quartile groups, stratified by %FMD. The %FMD showed a significant relationship with TDS (β = -0.47, P = 0.001), even after adjusting for confounding factors (β = -0.33, P = 0.02). In contrast, AHI, 3%ODI, averaged SpO2, lowest SpO2, and

CONCLUSIONS

This study shows the validity of TDS in predicting endothelial damage in patients with SDB. Cumulative hypoxemia, rather than the frequency of hypoxemic events presented as AHI, may be a greater contributing factor in causing endothelial dysfunction. A simple index like TDS may be a useful and novel indicator of the influence of SDB on the vasculature.

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Key Words

• blood pressure
• cardiovascular diseases
• endothelial function
• hypertension
• hypoxemia
• sleep-disordered breathing.

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MESH Headings

• Adult
• Aged
• Biomarkers/blood
• Endothelium, Vascular/physiopathology
• Female
• Humans
• Hyperemia/physiopathology
• Hypoxia/blood
• Hypoxia/diagnosis
• Hypoxia/etiology
• Hypoxia/physiopathology
• Male
• Middle Aged
• Oximetry
• Oxygen/blood
• Polysomnography
• Predictive Value of Tests
• Respiration
• Risk Factors
• Sleep
• Sleep Apnea Syndromes/complications
• Sleep Apnea Syndromes/diagnosis
• Sleep Apnea Syndromes/physiopathology
• Vascular Diseases/diagnosis
• Vascular Diseases/etiology
• Vascular Diseases/physiopathology
• Vasodilation

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Grants Collapse

Affiliation(s)

Hiroyuki Sawatari Department of Health Sciences, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
Akiko Chishaki Department of Health Sciences, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
Mari Nishizaka Sleep Apnea Center, Kyushu University Hospital, Fukuoka, Japan; Department of Cardiovascular Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
Tomotake Tokunou Department of Cardiovascular Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
Sonomi Adachi Sleep Apnea Center, Kyushu University Hospital, Fukuoka, Japan; Center for Clinical and Translational Research, Kyushu University Hospital, Fukuoka, Japan
Chikara Yoshimura Sleep Apnea Center, Kyushu University Hospital, Fukuoka, Japan
Tomoko Ohkusa Kirameki Projects Career Support Center, Kyushu University Hospital, Fukuoka, Japan
Shin-ichi Ando Sleep Apnea Center, Kyushu University Hospital, Fukuoka, Japan;

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Impact of Obstructive Sleep Apnea Syndrome on Endothelial Function, Arterial Stiffening, and Serum Inflammatory Markers: An Updated Meta-analysis and Metaregression of 18 Studies

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) has been indicated to contribute to the development of cardiovascular disease; however, the underlying mechanism remains unclear. This study aimed to test the hypothesis that OSAS may be associated with cardiovascular disease by elevating serum levels of inflammatory markers and causing arterial stiffening and endothelial dysfunction.

METHODS AND RESULTS

Related scientific reports published from January 1, 2006, to June 30, 2015, were searched in the following electronic literature databases: PubMed, Excerpta Medica Database, ISI Web of Science, Directory of Open Access Journals, and the Cochrane Library. The association of OSAS with serum levels of inflammatory markers, endothelial dysfunction, and arterial stiffening were investigated. Overall, 18 eligible articles containing 736 patients with OSAS and 424 healthy persons were included in this meta-analysis. Flow-mediated dilation in patients with moderate-severe OSAS was significantly lower than that in controls (standardized mean difference -1.02, 95% CI -1.31 to -0.73, P<0.0001). Carotid-femoral pulse wave velocity (standardized mean difference 0.45, 95% CI 0.21-0.69, P<0.0001), augmentation index (standardized mean difference 0.57, 95% CI 0.25-0.90, P<0.0001), and serum levels of high-sensitivity C-reactive protein and C-reactive protein (standardized mean difference 0.58, 95% CI 0.42-0.73, P<0.0001) were significantly higher in patients with OSAS than in controls.

CONCLUSION

OSAS, particularly moderate-severe OSAS, appeared to reduce endothelial function, increase arterial stiffness, and cause chronic inflammation, leading to the development of cardiovascular disease.

Patent Foramen Ovale Closure in Obstructive Sleep Apnea Improves Blood Pressure and Cardiovascular Function

Obstructive sleep apnea (OSA) is a frequent syndrome characterized by intermittent hypoxemia and increased prevalence of arterial hypertension and cardiovascular morbidity. In OSA, the presence of patent foramen ovale (PFO) is associated with increased number of apneas and more severe oxygen desaturation. We hypothesized that PFO closure improves sleep-disordered breathing and, in turn, has favorable effects on vascular function and arterial blood pressure. In 40 consecutive patients with newly diagnosed OSA, we searched for PFO. After initial cardiovascular assessment, the 14 patients with PFO underwent initial device closure and the 26 without PFO served as control group. Conventional treatment for OSA was postponed for 3 months in both groups, and polysomnographic and cardiovascular examinations were repeated at the end of the follow-up period. PFO closure significantly improved the apnea-hypopnea index (ΔAHI -7.9±10.4 versus +4.7±13.1 events/h, P=0.0009, PFO closure versus control), the oxygen desaturation index (ΔODI -7.6±16.6 versus +7.6±17.0 events/h, P=0.01), and the number of patients with severe OSA decreased significantly after PFO closure (79% versus 21%, P=0.007). The following cardiovascular parameters improved significantly in the PFO closure group, although remained unchanged in controls: brachial artery flow-mediated vasodilation, carotid artery stiffness, nocturnal systolic and diastolic blood pressure (-7 mm Hg, P=0.009 and -3 mm Hg, P=0.04, respectively), blood pressure dipping, and left ventricular diastolic function. In conclusion, PFO closure in OSA patients improves sleep-disordered breathing and nocturnal oxygenation. This translates into an improvement of endothelial function and vascular stiffening, a decrease of nighttime blood pressure, restoration of the dipping pattern, and improvement of left ventricular diastolic function.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01780207.

Predictive value of dynamic renal resistive index (DRIN) for renal outcome in type 2 diabetes and essential hypertension: a prospective study

BACKGROUND

Hypertension (EH) and type 2 diabetes (T2DM) are major causes of chronic kidney disease (CKD) and identification of predictors of CKD onset is advisable. We aimed to assess whether dynamic renal resistive index (DRIN), as well as other markers of systemic vascular damage, are able to predict albuminuria onset and estimated glomerular filtration rate (eGFR) decline in patients with T2DM or EH.

METHODS

In this prospective observational cohort study, 27 T2DM and 43 EH patients, free of CKD at baseline, were followed-up for 4.1 ± 0.6 years. Resistive Index (RI), endothelium-dependent (FMD) and independent vasodilation in the brachial artery (after glyceryl trinitrate - GTN - 25 μg s.l.), carotid-femoral Pulse Wave Velocity (PWV), Augmentation Index (AIx), DRIN (%RI change after GTN 25 μg s.l.) were evaluated.

RESULTS

Patients developing microalbuminuria were older, more frequently T2DM, with higher UACR at baseline, and showed higher DRIN (-2.8 ± 6.7 vs -10.6 ± 6.4 %, p = 0.01) and PWV (9.9 ± 1.3 vs 7.9 ± 1.5 m/s, p = 0.004) at baseline. The best predictors of microalbuminuria onset were DRIN > -5.16 % in T2DM (sensitivity 0.83, specificity 0.80) and PWV > 8.6 m/s in EH (sensitivity 0.96, specificity 1.00). Individuals whose eGFR declined (n = 27) had higher eGFR at baseline, but similar vascular characteristics; however in EH showing eGFR decline, baseline DRIN and PWV were higher. PWV showed a steeper progression during follow-up in patients developing albuminuria (Visit-outcome interaction: p = 0.01), while DRIN was early compromised but no further impaired (Visit-outcome interaction: p = 0.04).

CONCLUSIONS

PWV and DRIN are able to predict microalbuminuria onset in newly diagnosed EH and T2DM. DRIN is early compromised in T2DM patients developing microalbuminuria.

Intrarenal hemodynamic and oxidative stress in patients with obstructive sleep apnea syndrome

BACKGROUND

Oxygen desaturation and reoxygenation, related to intermittent hypoxia cycles due to upper airway obstruction, are major pathophysiologic features of obstructive sleep apnea syndrome (OSAS) and are thought to be responsible for an increased risk of cardiovascular diseases. Continuous positive airway pressure (CPAP) is therefore considered the gold standard in the management of OSAS. Further data demonstrated a high prevalence of OSAS in patients with altered renal function despite the underlying pathophysiological mechanisms that have not been clarified. This study aims to provide evidence on the reported high prevalence of endothelial dysfunction and alterations of the intrarenal hemodynamic in patients affected by OSAS. Furthermore, we evaluated the effect of a CPAP therapy on these endpoints.

METHODS

Twenty patients were enrolled in a prospective study and underwent ultrasound examination to assess endothelial dysfunction, by collecting brachial flow-mediated dilation (FMD) and intrarenal artery stiffness, pre- and post a 30-day treatment with CPAP.

RESULTS

Endothelial dysfunction and intrarenal artery stiffness significantly improved in all patients after a month of CPAP. In particular, we observed a significant reduction in the renal resistance index (RI) (p < 0.001) and systolic/diastolic ratio (S/D) ratio (p < 0.001) and a significant increase of FMD (p < 0.001). The apnea-hypopnea index (AHI) showed a negative correlation with Δ FMD (p < 0.05, r = -0.46). Conversely, a positive correlation exists between Δ RI and the oxygen desaturation index (ODI) (specificare la sigla) (p < 0.05, r = 0.46).

CONCLUSIONS

Our study firstly showed a significant effect of CPAP on renal perfusion and endothelial function in OSAS patients without concomitant cardiovascular comorbidities.

Nocturnal pulse rate and symptomatic response in patients with obstructive sleep apnoea treated with continuous positive airway pressure for one year

BACKGROUND

Obstructive sleep apnoea (OSA) is the most common form of sleep-disordered breathing and a known risk factor for cardiovascular disease. We hypothesised that in patients with OSA the characteristics of nocturnal pulse rate (PR) are associated with changes in blood pressure and daytime sleepiness, following commencement of continuous positive airway pressure (CPAP) therapy.

METHODS

Pulse oximetry data, demographics, daytime sleepiness and blood pressure were recorded at baseline and at one year follow up. Patients with OSA were grouped according to positive and negative changes in the PR (ΔPR) response during the first night of pulse oximetry before commencement of CPAP.

RESULTS

A total of 115 patients (58 with OSA and 57 matched subjects without OSA) were identified and included in the analysis. The scale of improvement in daytime sleepiness could be predicted by a negative or positive ΔPR, as recorded in the initial screening pulse oximetry [ΔESS -5.8 (5.1) vs. -0.8 (7.2) points, P<0.05]. A negative correlation was observed between mean nocturnal PR and changes in systolic blood pressure (SBP) after one year of CPAP treatment (r=-0.42, P<0.05).

CONCLUSIONS

Mean nocturnal PR prior to CPAP initiation was associated with changes in SBP at one year follow up. A descending nocturnal PR in patients with OSA, prior to CPAP initiation, might help to identify a symptomatic response from long term CPAP treatment.

Cardiovascular function in healthy Himalayan high-altitude dwellers

BACKGROUND

Residents of the Himalayan valleys uniquely adapted to their hypoxic environment in terms of pulmonary vasculature, but their systemic vascular function is still largely unexplored. The aim of the study was to investigate vascular function and structure in rural Sherpa population, permanently living at high altitude in Nepal (HA), in comparison with control Caucasian subjects (C) living at sea level.

METHODS AND RESULTS

95 HA and 64 C were enrolled. Cardiac ultrasound, flow-mediated dilation (FMD) of the brachial artery, carotid geometry and stiffness, and aortic pulse wave velocity (PWV) were performed. The same protocol was repeated in 11 HA with reduced FMD, after 1-h 100% O2 administration. HA presented lower FMD (5.18 ± 3.10 vs. 6.44  ±  2.91%, p = 0.02) and hyperemic velocity than C (0.61 ± 0.24 vs. 0.75 ± 0.28 m/s, p = 0.008), while systolic pulmonary pressure was higher (29.4 ± 5.5 vs. 23.6 ± 4.8 mmHg, p < 0.0001). In multiple regression analysis performed in HA, hyperemic velocity remained an independent predictor of FMD, after adjustment for baseline brachial artery diameter, room temperature and pulse pressure, explaining 8.7% of its variance. On the contrary, in C brachial artery diameter remained the only independent predictor of FMD, after adjustment for confounders. HA presented also lower carotid IMT than C (0.509 ± 0.121 vs. 0.576 ± 0.122 mm, p < 0.0001), higher diameter (6.98 ± 1.07 vs. 6.81 ± 0.85 mm, p = 0.004 adjusted for body surface area) and circumferential wall stress (67.6 ± 13.1 vs. 56.4 ± 16.0 kPa, p < 0.0001), while PWV was similar. O2 administration did not modify vascular variables.

CONCLUSIONS

HA exhibit reduced NO-mediated dilation in the brachial artery, which is associated to reduced hyperemic response, indicating microcirculatory dysfunction. A peculiar carotid phenotype, characterized by reduced IMT and enlarged diameter, was also found.

Secondary arterial hypertension: when, who, and how to screen?

Secondary hypertension refers to arterial hypertension due to an identifiable cause and affects ∼5-10% of the general hypertensive population. Because secondary forms are rare and work up is time-consuming and expensive, only patients with clinical suspicion should be screened. In recent years, some new aspects gained importance regarding this screening. In particular, increasing evidence suggests that 24 h ambulatory blood pressure (BP) monitoring plays a central role in the work up of patients with suspected secondary hypertension. Moreover, obstructive sleep apnoea has been identified as one of the most frequent causes. Finally, the introduction of catheter-based renal denervation for the treatment of patients with resistant hypertension has dramatically increased the interest and the number of patients evaluated for renal artery stenosis. We review the clinical clues of the most common causes of secondary hypertension. Specific recommendations are given as to evaluation and treatment of various forms of secondary hypertension. Despite appropriate therapy or even removal of the secondary cause, BP rarely ever returns to normal with long-term follow-up. Such residue hypertension indicates either that some patients with secondary hypertension also have concomitant essential hypertension or that irreversible vascular remodelling has taken place. Thus, in patients with potentially reversible causes of hypertension, early detection and treatment are important to minimize/prevent irreversible changes in the vasculature and target organs.