Arterial Stiffness as a Cause of Resistant Hypertension?

Assessment of Arterial Stiffness in Patients With Resistant Hypertension: Additional Insights Into the Pathophysiology of This Condition?

BACKGROUND

Good understanding of the pathophysiological mechanism(s) of resistant hypertension (RH) and the relationship to vascular dysfunction is important for optimal blood pressure control.

METHODS AND RESULTS

The aim of this review article is to summarize the available data on the methods of arterial stiffness assessment, and their usefulness in RH. Several studies that provide information on the noninvasive methods of evaluation of arterial stiffness have been discussed; specifically, pulse wave velocity (PWV) and augmentation index (AIx) tests. Increased arterial stiffness, elevated AIx, and impaired endothelial function all act as indicators and predictors of cardiovascular events in patients with hypertension (HTN).

CONCLUSION

Our review suggests that PWV and AIx are impaired in patients with severe HTN. Early assessment of these characteristics can potentially be of value in patients with RH.

Neurohumoral and Endothelial Responses to Heated Water-Based Exercise in Resistant Hypertensive Patients

BACKGROUND

The neurohumoral and endothelial responses to the blood pressure (BP) lowering effects of heated water-based exercise (HEx) in resistant hypertension (HT) patients remain undefined.Methods and Results:We investigated these in 44 true resistant HT patients (age 53.3±0.9 years, mean±SEM). They were randomized and allocated to 2 groups, 28 to a HEx training protocol, which consisted of callisthenic exercises and walking in a heated pool for 1 h, three times weekly for 12 weeks and 16 patients to a control group maintaining their habitual activities. Measurements made before and after 12 weeks of HEx included clinic and 24-h BP, plasma levels of nitric oxide, endothelin-1, aldosterone, renin, norepinephrine and epinephrine, as well as peak V̇O₂, and endothelial function (reactive hyperemia). After 12 weeks of HEx patients showed a significant decrease in clinic and 24-h systolic and diastolic BPs. Concomitantly, nitric oxide increased significantly (from 25±8 to 75±24 μmol/L, P<0.01), while endothelin-1 (from 41±5 to 26±3 pg/mL), renin (from 35±4 to 3.4±1 ng/mL/h), and norepinephrine (from 720±54 to 306±35 pg/mL) decreased significantly (P<0.01). Plasma aldosterone also tended to decrease, although not significantly (from 101±9 to 76±4 pg/mL, P=NS). Peak V̇O₂increased significantly after HEx (P<0.01), while endothelial function was unchanged. No significant change was detected in the control group.

CONCLUSIONS

The BP-lowering effects of HEx in resistant HT patients were accompanied by a significant reduction in the marked neurohumoral activation characterizing this clinical condition.

Obstructive Sleep Apnea and Vascular Diseases

Obstructive sleep apnea (OSA) affects a large proportion of adults, and is as an independent risk factor for cerebrovascular and cardiovascular disease. The repetitive airway obstruction that characterizes OSA results in intermittent hypoxia, intrathoracic pressure swings, and sleep fragmentation, which in turn lead to sympathetic activation, oxidative stress, inflammation, and endothelial dysfunction. This review outlines the associations between OSA and vascular diseases and describes basic mechanisms that may be responsible for this association, in both the micro- and macrocirculation. It also reports on interventional studies that aim to ameliorate OSA and thereby reduce vascular disease burden. © 2016 American Physiological Society. Compr Physiol 6:1519-1528, 2016.

Central iliac arteriovenous anastomosis for hypertension: targeting mechanical aspects of the circulation

Raised blood pressure is the leading attributable risk factor for global morbidity and mortality. Real world data demonstrates that half of treated patients are at elevated cardiovascular risk because of inadequately controlled BP. In addition to pharmacotherapy, certain interventional strategies to reduce blood pressure and cardiovascular risk in hypertension can be considered according to international guidelines. One of the newer technologies entering this field is a proprietary arteriovenous coupler device that forms a fixed flow arteriovenous conduit in the central vasculature. In this review, we examine the development of and rationale for the creation of a central arteriovenous anastomosis in patients with hypertension and review the proposed mechanisms by which it may ameliorate hypertension. We critically review the clinical trial evidence base to date and postulate on future therapeutic directions.

Pathogenesis of drug-resistant hypertension

More is known about the epidemiology of drug-resistant hypertension than particular pathogenic factors and pathways. Several recurring themes, however, seem evident on using insight from epidemiology and general knowledge of the pathophysiology of hypertension. Specifically, 4 main pathways converge on drug resistance including sodium handling, sympathetic nervous system activation, endothelial dysfunction, and arterial stiffness. These factors, and the various pathways and elements contributing to them, are reviewed. In addition to describing how these factors exert their individual influences on resistant hypertension, several examples of how interactions between these factors, particularly in the case of chronic kidney disease, are included. At the conclusion of this review some thoughts are offered on additional mechanisms and areas for potential research.

Relationship between resistant hypertension and arterial stiffness assessed by brachial-ankle pulse wave velocity in the older patient

Background

Resistant hypertension (RH) is a common clinical condition associated with increased cardiovascular mortality and morbidity in older patients. Several factors and conditions interfering with blood pressure (BP) control, such as excess sodium intake, obesity, diabetes, older age, kidney disease, and certain identifiable causes of hypertension are common in patients resistant to antihypertensive treatment. Arterial stiffness, measured by brachial-ankle pulse wave velocity (baPWV), is increasingly recognized as an important prognostic index and potential therapeutic target in hypertensive patients. The aim of this study was to determine whether there is an association between RH and arterial stiffness.

Methods

This study included 1,620 patients aged ≥65 years who were referred or self-referred to the outpatient hypertension unit located at a single cardiovascular center. They were separated into normotensive, controlled BP, and resistant hypertension groups. Home BP, blood laboratory parameters, echocardiographic studies and baPWV all were measured.

Results

The likelihood of diabetes mellitus was significantly greater in the RH group than in the group with controlled BP (odds ratio 2.114, 95% confidence interval [CI] 1.194–3.744, P=0.010). Systolic BP was correlated in the RH group significantly more than in the group with controlled BP (odds ratio 1.032, 95% CI 1.012–1.053, P=0.001). baPWV (odds ratio 1.084, 95% CI 1.016–1.156, P=0.015) was significantly correlated with the presence of RH. The other factors were negatively correlated with the existence of RH.

Conclusion

In patients aged ≥65 years, the patients with RH have elevated vascular stiffness more than the well controlled hypertension group. baPWV increased with arterial stiffness and was correlated with BP levels. Strict BP control is necessary to prevent severe functional and structural vascular changes in the course of hypertensive disease.

[Resistant arterial hypertension in Primary Care patients in Spain. PRESCAP Study 2010]

OBJECTIVE

To determine the prevalence and clinical and epidemiological characteristics of Primary Care patients with resistant hypertension (RHT) in Spain.

PATIENTS AND METHODS

A cross-sectional multicenter study was conducted on hypertensive patients aged 18 or over and seen in a Primary Care clinic. RHT was considered as the presence of uncontrolled blood pressure in patients treated with at least 3 drugs, one of which is a diuretic.

RESULTS

Of the 12,961 hypertensive patients in the PRESCAP 2010 study, 962 (7.4%) fulfilled criteria for RHT, of whom 51% were women, and with a mean age (SD) 68.8 [11.4] years. Patients with RHT were older (68.80 [10.69] years vs. 66.06 [11.44] years, P<.001), had a higher prevalence of obesity (55.2 vs. 38.6%, P<.001), a higher waist circumference (103.90 [13.89] vs. 99.32 [13.69] cm, P<.001), and a higher prevalence of DM (48.3 vs. 29.5%, P<.001). The prevalence of target organ damage (73.0 vs. 61.4%, P<.001) and cardiovascular disease (46.7 vs. 26.8%, P<.001) were higher in patients with resistant hypertension. The multivariate analysis showed that the variables associated with resistant hypertension were the presence of cardiovascular disease, diabetes mellitus, sedentary life style, microalbuminuria, body mass index, duration of AHT, and triglycerides.

CONCLUSIONS

The prevalence of RHT in Primary Care patients is related to inappropriate lifestyles, the presence of target organ damage, and cardiovascular disease.

Definition, identification and treatment of resistant hypertension in chronic kidney disease patients

Resistant hypertension, the inability to achieve goal blood pressure despite the use of three or more appropriately dosed antihypertensive drugs (including a diuretic), remains a common clinical problem, especially in patients with chronic kidney disease (CKD). While the exact prevalence and prognosis of resistant hypertension in CKD patients remain unknown, resistant hypertension likely contributes significantly to increased cardiovascular risk and progression of kidney disease in this population. We review the identification and evaluation of patients with resistant hypertension, including the importance of 24-h ambulatory blood pressure monitoring in the identification of 'white-coat', 'masked' and 'non-dipper' hypertension, the latter of which has particular clinical and therapeutic importance in patients with resistant hypertension and CKD. We then discuss treatment strategies for resistant hypertension that target the pathophysiologic mechanisms underlying resistance to treatment, including persistent volume excess, incomplete renin-angiotensin-aldosterone system blockade and inadequate nocturnal blood pressure control. Finally, we propose a treatment algorithm for evaluation and treatment of resistant hypertension in patients with CKD.

Resistant hypertension and target organ damage

Cardiovascular (CV) complications such as myocardial infarction, heart failure, stroke and renal failure are related to both the degree and the duration of blood pressure (BP) increase. Resistant hypertension (RH) is associated with a higher risk of CV complications and a higher prevalence of target organ damage (TOD). The relationship between CV disease and TOD can be bidirectional. Elevated BP in RH may cause CV structural and functional alterations, and the development or persistence of left ventricular hypertrophy, aortic stiffness, atherosclerotic plaques, microvascular disease and renal dysfunction, may render hypertension more difficult to control. Specifically, RH is related to several conditions, including obesity, sleep apnea, diabetes, metabolic syndrome and hyperaldosteronism, characterized by an overexpression of humoral and hormonal factors that are involved in the development and maintenance of TOD. Optimal therapeutic strategies, including pharmacological treatment and innovative invasive methodologies, have been shown to achieve adequate BP control and induce the regression of TOD, thereby potentially improving patient prognosis.

Aerobic exercise reduces blood pressure in resistant hypertension

Regular physical exercise is broadly recommended by current European and American hypertension guidelines. It remains elusive, however, whether exercise leads to a reduction of blood pressure in resistant hypertension as well. The present randomized controlled trial examines the cardiovascular effects of aerobic exercise on resistant hypertension. Resistant hypertension was defined as a blood pressure ≥140/90 mm Hg in spite of 3 antihypertensive agents or a blood pressure controlled by ≥4 antihypertensive agents. Fifty subjects with resistant hypertension were randomly assigned to participate or not to participate in an 8- to 12-week treadmill exercise program (target lactate, 2.0±0.5 mmol/L). Blood pressure was assessed by 24-hour monitoring. Arterial compliance and cardiac index were measured by pulse wave analysis. The training program was well tolerated by all of the patients. Exercise significantly decreased systolic and diastolic daytime ambulatory blood pressure by 6±12 and 3±7 mm Hg, respectively (P=0.03 each). Regular exercise reduced blood pressure on exertion and increased physical performance as assessed by maximal oxygen uptake and lactate curves. Arterial compliance and cardiac index remained unchanged. Physical exercise is able to decrease blood pressure even in subjects with low responsiveness to medical treatment. It should be included in the therapeutic approach to resistant hypertension.

The relationship between resistant hypertension and arterial stiffness

OBJECTIVES

With growing awareness of arterial stiffness (AS) in the past 10 years, it was realized that resistant hypertension (RH) and AS share the same associated conditions such as older age, isolated systolic hypertension (HT), obesity, chronic kidney disease (CKD), and so on. Until now, there is no study investigating the role of AS in RH. In our study we aimed to determine whether there is an association between RH and AS.

METHODS

Among 87 patients enrolled in this study, 30 were resistant hypertensives (Group 1), 29 were controlled hypertensives (Group 2), and 28 were normotensives (Group 3). Arterial stiffness was measured by both applanation tonometry and echocardiography; augmentation index, pulse wave velocity (PWV), aortic strain, and aortic distensibility were recorded in each patient. Diastolic function parameters were also assessed.

RESULTS

In resistant hypertensive group, augmentation index and PWV were significantly higher than Group 2 and Group 3 (P = .03 and P < .01). Aortic strain and aortic distensibility parameters were significantly lower in RH group (P < .01 and P < .01). Arterial stiffness parameters were similar among Group 2 and Group 3. Among diastolic function parameters, left atrial volume index and left ventricular mass index significantly differ between groups. These two parameters were significantly lower in control group (P < .01 and P = .02) whereas similar in Group 1 and Group 2. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels were significantly different between groups as expected. When the correlation between two methods of AS was analyzed, a significant strong inverse correlation was found between echocardiographic and tonometric parameters.

CONCLUSION

Arterial stiffness was found to be associated with RH. The inconsistency of this association in controlled hypertensives suggests a possible role of AS in RH pathogenesis. This study also showed that aortic strain and distensibility correlate well with the PWV which is the gold standard in the assessment of AS. This finding is important for the evaluation of AS more commonly in daily practice as echocardiography is a more feasible device than applanation tonometry.

Resistant hypertension workup and approach to treatment

Resistant hypertension is defined as blood pressure above the patient's goal despite the use of 3 or more antihypertensive agents from different classes at optimal doses, one of which should ideally be a diuretic. Evaluation of patients with resistive hypertension should first confirm that they have true resistant hypertension by ruling out or correcting factors associated with pseudoresistance such as white coat hypertension, suboptimal blood pressure measurement technique, poor adherence to prescribed medication, suboptimal dosing of antihypertensive agents or inappropriate combinations, the white coat effect, and clinical inertia. Management includes lifestyle and dietary modification, elimination of medications contributing to resistance, and evaluation of potential secondary causes of hypertension. Pharmacological treatment should be tailored to the patient's profile and focus on the causative pathway of resistance. Patients with uncontrolled hypertension despite receiving an optimal therapy are candidates for newer interventional therapies such as carotid baroreceptor stimulation and renal denervation.

Efficacy of spironolactone therapy in patients with true resistant hypertension

The role of spironolactone in resistant hypertension management is unclear. The aim of this prospective trial was to evaluate the antihypertensive effect of spironolactone in patients with true resistant hypertension diagnosed by ambulatory blood pressure monitoring. A total of 175 patients had clinical and complementary exams obtained at baseline and received spironolactone in doses of 25 to 100 mg/d. A second ambulatory blood pressure monitoring was performed after a median interval of 7 months. Paired Student t test was used to assess differences in blood pressure before and during spironolactone administration, and multivariate analysis adjusted for age, sex, and number of antihypertensive drugs to assess the predictors of blood pressure fall. There were mean reductions of 16 and 9 mm Hg, respectively, in 24-hour systolic and diastolic blood pressures (95% CIs: 13 to 18 and 7 to 10 mm Hg; P<0.001). Office systolic blood pressure and diastolic blood pressure also decreased (14 and 7 mm Hg). Controlled ambulatory blood pressure was reached in 48% of patients. Factors associated with better response were higher waist circumference, lower aortic pulse wave velocity, and lower serum potassium. No association with plasma aldosterone or aldosterone:renin ratio was found. Adverse effects were observed in 13 patients (7.4%). A third ambulatory blood pressure monitoring performed in 78 patients after a median of 15 months confirmed the persistence of the spironolactone effect. In conclusion, spironolactone administration to true resistant hypertensive patients is safe and effective in decreasing blood pressure, especially in those with abdominal obesity and lower arterial stiffness. Its addition to an antihypertensive regimen as the fourth or fifth drug is recommended.

Clinical approach in treatment of resistant hypertension

Resistant hypertension, defined as failure to achieve target blood pressure despite the use of optimal or maximum doses of at least 3 agents, one of which is a diuretic, or requiring 4 or more medications to achieve blood pressure goal, is likely to affect up to 20% of all patients with hypertension. Apparent resistant hypertension may be caused by medication nonadherence, substances that either interfere with antihypertensive mediations or cause blood pressure elevation, and under- or inappropriate medication treatment. Certain patient characteristics are associated with the presence of resistant hypertension and include chronic kidney disease, diabetes, obesity, and presence of end-organ damage (microalbuminuria, retinopathy, left-ventricular hypertrophy). Secondary causes of resistant hypertension are not uncommon and include obstructive sleep apnea, chronic kidney disease, primary aldosteronism, renal artery stenosis, pheochromocytoma, and Cushing's disease. Initial medication management usually includes adding or increasing the dose of a diuretic, which is effective in lowering the blood pressure of a large number of patients with resistant hypertension. Additional management options include maximizing lifestyle modification, combination therapy of antihypertensive agents depending on individual patient characteristics, adding less-commonly used fourth- or fifth-line antihypertensive agents, and referral to a hypertension specialist.

Resistant hypertension

Resistant hypertension is most often due to insufficient medical therapy. With a patient history, physical examination and focused laboratory tests, sufficient information can be gathered to lead to further directed medical therapy, which most often includes a diuretic as part of the drug regimen. Patients may require four or more classes of antihypertensives, some at high doses to achieve control. The clinician must be prepared to use sufficient medications at sufficient doses to achieve blood pressure targets. Referral to a hypertension specialist is appropriate if blood pressure remains uncontrolled despite therapy with three antihypertensive medications.

Vascular compliance and arterial calcification: impact on blood pressure reduction

PURPOSE OF REVIEW

The aim of this article is to review the relationship between vascular calcification and difficult to control hypertension. This does not address antihypertensive treatment of drug resistant hypertension per se.

RECENT FINDINGS

Vascular calcification occurs in a variety of common hypertension scenarios. Basic mechanisms of how and why vessels calcify are reviewed including new genetic insights. The potential for contributing to or improving calcification through drug therapies for nonhypertensive disorders is reviewed.

SUMMARY

Vascular calcification is common and easily recognized. Studies that target its clinical consequences (arterial stiffness) as primary treatment goals are needed.