Blood Pressure Variability in Clinical Practice: Past, Present and the Future

Recent advances in wearable technology through convenient and cuffless systems will enable continuous, noninvasive monitoring of blood pressure (BP), heart rate, and heart rhythm on both longitudinal 24-hour measurement scales and high-frequency beat-to-beat BP variability and synchronous heart rate variability and changes in underlying heart rhythm. Clinically, BP variability is classified into 4 main types on the basis of the duration of monitoring time: very-short-term (beat to beat), short-term (within 24 hours), medium-term (within days), and long-term (over months and years). BP variability is a strong risk factor for cardiovascular diseases, chronic kidney disease, cognitive decline, and mental illness. The diagnostic and therapeutic value of measuring and controlling BP variability may offer critical targets in addition to lowering mean BP in hypertensive populations.

Rationale and Design of Sympathetic Mapping/Ablation of Renal Nerves Trial (SMART) for the Treatment of Hypertension: a Prospective, Multicenter, Single-Blind, Randomized and Sham Procedure-Controlled Study

Renal denervation (RDN) is proposed as a durable and patient compliance independent treatment for hypertension. However, 20-30% non-responder after RDN treatment weakened the therapeutic effect, which may be due to blind ablation. The renal nerve mapping/selective ablation system developed by SyMap Medical Ltd (Suzhou), China, has the function of mapping renal sympathetic/parasympathetic nerve sites and selectively removing renal sympathetic nerves and is expected to meet the urgent unmet clinical need of targeted RDN. The "Sympathetic Mapping/Ablation of Renal Nerves Trial" (SMART) is a prospective, multicenter, randomized, single-blinded, sham procedure-controlled trial, to evaluate the safety and efficacy of targeted renal sympathetic denervation in patients with essential and uncontrolled hypertension. The study is the first clinical registry trial using a targeted RDN for the treatment of uncontrolled hypertension; the dual-endpoint design can answer the question of how many antihypertensive drugs can be reduced in patients after RDN. The trial is registered on clinicaltrials.gov NCT02761811.

The Clinical Problem of Pelvic Venous Disorders

Pelvic venous disorders are inter-related pathologic conditions caused by reflux and obstruction in the pelvic veins. It can present a spectrum of clinical features based on the route of transmission of venous hypertension to either distal or caudal venous reservoirs. Imaging can help to visualize pelvic vascular and visceral structures to rule out other gynecologic, gastrointestinal, and urologic diseases. Endovascular treatment, owing to its low invasive nature and high success rate, has become the mainstay in the management of pelvic venous disorders. This article reviews the pathophysiology, clinical presentations, and diagnostic and therapeutic approaches to pelvic venous disorders.

Splanchnic nerve modulation in heart failure: mechanistic overview, initial clinical experience, and safety considerations

Volume recruitment from the splanchnic compartment is an important physiological response to stressors such as physical activity and blood loss. In the setting of heart failure (HF), excess fluid redistribution from this compartment leads to increased cardiac filling pressures with limitation in exercise capacity. Recent evidence suggests that blocking neural activity of the greater splanchnic nerve (GSN) could have significant benefits in some patients with HF by reducing cardiac filling pressures and improving exercise capacity. However, to date the long-term safety of splanchnic nerve modulation (SNM) in the setting of HF is unknown. SNM is currently used in clinical practice to alleviate some forms of chronic abdominal pain. A systematic review of the series where permanent SNM was used as a treatment for chronic abdominal pain indicates that permanent SNM is well tolerated, with side-effects limited to transient diarrhoea or abdominal colic and transient hypotension. The pathophysiological role of the GSN in volume redistribution, the encouraging findings of acute and chronic pilot SNM studies and the safety profile from permanent SNM for pain provides a strong basis for continued efforts to study this therapeutic target in HF.

Extracardiac Abnormalities of Preload Reserve: Mechanisms Underlying Exercise Limitation in Heart Failure with Preserved Ejection Fraction, Autonomic Dysfunction, and Liver Disease

While many of the cardiac limitations to exercise performance are now well-characterized, extracardiac limitations to exercise performance have been less well recognized but are nevertheless important. We propose that abnormalities of cardiac preload reserve represents an under-recognized but common cause of exercise limitations. We further propose that mechanistic links exist between conditions as seemingly disparate as heart failure with preserved ejection fraction, nonalcoholic fatty liver disease, and pelvic venous compression/obstruction syndromes (eg, May-Thurner). We conclude that extracardiac abnormalities of preload reserve serve as a major pathophysiologic mechanism underlying these and other disease states.

Iliocaval Venous Obstruction, Cardiac Preload Reserve and Exercise Limitation

Cardiac output during exercise increases by as much as fivefold in the untrained man, and by as much as eightfold in the elite athlete. Increasing venous return is a critical but much overlooked component of the physiological response to exercise. Cardiac disorders such as constrictive pericarditis, restrictive cardiomyopathy and pulmonary hypertension are recognised to impair preload and cause exercise limitation; however, the effects of peripheral venous obstruction on cardiac function have not been well described. This manuscript will discuss how obstruction of the iliocaval venous outflow can lead to impairment in exercise tolerance, how such obstructions may be diagnosed, the potential implications of chronic obstructions on sympathetic nervous system activation, and relevance of venous compression syndromes in heart failure with preserved ejection fraction.

Correlation of Quantitated Intravascular Volume with Blood Pressure in Patients with Systemic Hypertension

Volume management is an essential component of anti-hypertensive therapy. Different volume phenotypes have been proposed. We sought to study the total blood volume (TBV), plasma volume (PV), and red blood cell volume (RBV) in hypertensive patients. We included patients followed in an outpatient cardiology clinic from 1998 to 2003. Blood volume (BV) parameters were measured using radioisotope iodine-131-labeled albumin dilution technique. Values were expressed as percentage (%) deviation from ideal volumes. A total of 95 patients were included. The intravascular volume distribution as percent deviation from normal volume ranged from - 23 to + 28% for TBV, - 22 to + 36% for PV and - 29 to + 37% for RBV. There was no significant correlation between systolic BP and any of the BV parameters (TBV and SBP, r = - 0.03; PV and SBP, r = - 0.12; RBV and SBP, r = - 0.08). Patients with hypertension have a wide variation in BV parameters. BV does not correlate with SBP.

Prediction of readmissions and mortality in patients with heart failure: lessons from the IMPEDANCE-HF extended trial

Aims

Readmissions for heart failure (HF) are a major burden. We aimed to assess whether the extent of improvement in pulmonary fluid content (ΔPC) during HF hospitalization evaluated by lung impedance (LI), or indirectly by other clinical and laboratory parameters, predicts readmissions.

Methods and results

The present study is based on pre‐defined secondary analysis of the IMPEDANCE‐HF extended trial comprising 266 HF patients at New York Heart Association Class II–IV and left ventricular ejection fraction ≤ 35% randomized to LI‐guided or conventional therapy during long‐term follow‐up. Lung impedance‐guided patients were followed for 58 ± 36 months and the control patients for 46 ± 34 months (P < 0.01) accounting for 253 and 478 HF hospitalizations, respectively (P < 0.01). Lung impedance, N‐terminal pro‐brain natriuretic peptide, weight, radiological score, New York Heart Association class, lung rales, leg oedema, or jugular venous pressure were measured at admission and discharge on each hospitalization in both groups with the difference defined as ΔPC. Average LI‐assessed ΔPC was 12.1% vs. 9.2%, and time to HF readmission was 659 vs. 306 days in the LI‐guided and control groups, respectively (P < 0.01). Lung impedance‐based ΔPC predicted 30 and 90 day HF readmission better than ΔPC assessed by the other variables (P < 0.01). The readmission rate for HF was lower if ΔPC > median compared with ΔPC ≤ median for all parameters evaluated in both study groups with the most pronounced difference predicted by LI (P < 0.01). Net reclassification improvement analysis showed that adding LI to the traditional clinical and laboratory parameters improved the predictive power significantly.

Conclusions

The extent of ΔPC improvement, primarily the LI based, during HF‐hospitalization, and study group allocation strongly predicted readmission and event‐free survival time.

Selective vs. Global Renal Denervation: a Case for Less Is More

PURPOSE OF REVIEW

Review the renal nerve anatomy and physiology basics and explore the concept of global vs. selective renal denervation (RDN) to uncover some of the fundamental limitations of non-targeted renal nerve ablation and the potential superiority of selective RDN.

RECENT FINDINGS

Recent trials testing the efficacy of RDN showed mixed results. Initial investigations targeted global RDN as a therapeutic goal. The repeat observation of heterogeneous response to RDN including non-responders with lack of a BP reduction, or even more unsettling, BP elevations after RDN has raised concern for the detrimental effects of unselective global RDN. Subsequent studies have suggested the presence of a heterogeneous fiber population and the potential utility of renal nerve stimulation to identify sympatho-stimulatory fibers or "hot spots." The recognition that RDN can produce heterogeneous afferent sympathetic effects both change therapeutic goals and revitalize the potential of therapeutic RDN to provide significant clinical benefits. Renal nerve stimulation has emerged as potential tool to identify sympatho-stimulatory fibers, avoid sympatho-inhibitory fibers, and thus guide selective RDN.

Central Iliac Arteriovenous Anastomosis for Uncontrolled Hypertension: One-Year Results From the ROX CONTROL HTN Trial

Creation of a central iliac arteriovenous anastomosis using a novel nitinol coupler device results in an immediate, significant reduction of blood pressure (BP). We present efficacy and safety findings at 12 months post-coupler insertion. This open-label, multicenter, prospective, randomized trial enrolled patients with a baseline office systolic BP ≥140 mm Hg and average daytime ambulatory BP ≥135/85 mm Hg. Subjects were randomly allocated to coupler implantation and continuing previous pharmacotherapy or to maintain previous treatment alone. At 12 months, 39 patients who had coupler therapy were included in the intention-to-treat analysis. Office-based systolic BP reduced by 25.1±23.3 mm Hg (baseline, 174±18 mm Hg; P<0.0001) post-coupler placement, and office diastolic BP reduced by 20.8±13.3 mm Hg (baseline, 100±13 mm Hg; P<0.0001). Mean 24-hour ambulatory BP reduced by 12.6±17.4/15.3±9.7 mm Hg (P<0.0001 for both). In a prespecified subset of patients who failed to respond adequately to prior renal denervation, coupler therapy led to highly significant reduction in office systolic/diastolic BP (30.7/24.1 mm Hg) and significant reduction in 24-hour ambulatory systolic/diastolic BP (12.4/14.4 mm Hg) at 12 months (n=9). After coupler therapy, 14 patients (33%) developed ipsilateral venous stenosis; all were treated successfully with venous stenting. These findings confirm the importance of arterial mechanics in the pathophysiology of hypertension and support the clinical use of a central iliac arteriovenous anastomosis.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01642498.

Interventional procedures and future drug therapy for hypertension

Hypertension management poses a major challenge to clinicians globally once non-drug (lifestyle) measures have failed to control blood pressure (BP). Although drug treatment strategies to lower BP are well described, poor control rates of hypertension, even in the first world, suggest that more needs to be done to surmount the problem. A major issue is non-adherence to antihypertensive drugs, which is caused in part by drug intolerance due to side effects. More effective antihypertensive drugs are therefore required which have excellent tolerability and safety profiles in addition to being efficacious. For those patients who either do not tolerate or wish to take medication for hypertension or in whom BP control is not attained despite multiple antihypertensives, a novel class of interventional procedures to manage hypertension has emerged. While most of these target various aspects of the sympathetic nervous system regulation of BP, an additional procedure is now available, which addresses mechanical aspects of the circulation. Most of these new devices are supported by early and encouraging evidence for both safety and efficacy, although it is clear that more rigorous randomized controlled trial data will be essential before any of the technologies can be adopted as a standard of care.

Effect of Arteriovenous Anastomosis on Blood Pressure Reduction in Patients With Isolated Systolic Hypertension Compared With Combined Hypertension

Background

Options for interventional therapy to lower blood pressure (BP) in patients with treatment‐resistant hypertension include renal denervation and the creation of an arteriovenous anastomosis using the ROX coupler. It has been shown that BP response after renal denervation is greater in patients with combined hypertension (CH) than in patients with isolated systolic hypertension (ISH). We analyzed the effect of ROX coupler implantation in patients with CH as compared with ISH.

Methods and Results

The randomized, controlled, prospective ROX Control Hypertension Study included patients with true treatment‐resistant hypertension (office systolic BP ≥140 mm Hg, average daytime ambulatory BP ≥135/85 mm Hg, and treatment with ≥3 antihypertensive drugs including a diuretic). In a post hoc analysis, we stratified patients with CH (n=31) and ISH (n=11). Baseline office systolic BP (177±18 mm Hg versus 169±17 mm Hg, P=0.163) and 24‐hour ambulatory systolic BP (159±16 mm Hg versus 154±11 mm Hg, P=0.463) did not differ between patients with CH and those with ISH. ROX coupler implementation resulted in a significant reduction in office systolic BP (CH: −29±21 mm Hg versus ISH: −22±31 mm Hg, P=0.445) and 24‐hour ambulatory systolic BP (CH: −14±20 mm Hg versus ISH: −13±15 mm Hg, P=0.672), without significant differences between the two groups. The responder rate (office systolic BP reduction ≥10 mm Hg) after 6 months was not different (CH: 81% versus ISH: 82%, P=0.932).

Conclusions

Our data suggest that creation of an arteriovenous anastomosis using the ROX coupler system leads to a similar reduction of office and 24‐hour ambulatory systolic BP in patients with combined and isolated systolic hypertension.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01642498.

Unilateral Carotid Body Resection in Resistant Hypertension: A Safety and Feasibility Trial

Animal and human data indicate pathological afferent signaling emanating from the carotid body that drives sympathetically mediated elevations in blood pressure in conditions of hypertension. This first-in-man, proof-of-principle study tested the safety and feasibility of unilateral carotid body resection in 15 patients with drug-resistant hypertension. The procedure proved to be safe and feasible. Overall, no change in blood pressure was found. However, 8 patients showed significant reductions in ambulatory blood pressure coinciding with decreases in sympathetic activity. The carotid body may be a novel target for treating an identifiable subpopulation of humans with hypertension.

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.

Central arteriovenous anastomosis for the treatment of patients with uncontrolled hypertension (the ROX CONTROL HTN study): a randomised controlled trial

BACKGROUND

Hypertension contributes to cardiovascular morbidity and mortality. We assessed the safety and efficacy of a central iliac arteriovenous anastomosis to alter the mechanical arterial properties and reduce blood pressure in patients with uncontrolled hypertension.

METHODS

We enrolled patients in this open-label, multicentre, prospective, randomised, controlled trial between October, 2012, and April, 2014. Eligible patients had baseline office systolic blood pressure of 140 mm Hg or higher and average daytime ambulatory blood pressure of 135 mm Hg or higher systolic and 85 mm Hg or higher diastolic despite antihypertensive treatment. Patients were randomly allocated in a 1:1 ratio to undergo implantation of an arteriovenous coupler device plus current pharmaceutical treatment or to maintain current treatment alone (control). The primary endpoint was mean change from baseline in office and 24 h ambulatory systolic blood pressure at 6 months. Analysis was by modified intention to treat (all patients remaining in follow-up at 6 months). This trial is registered with ClinicalTrials.gov, number NCT01642498.

FINDINGS

83 (43%) of 195 patients screened were assigned arteriovenous coupler therapy (n=44) or normal care (n=39). Mean office systolic blood pressure reduced by 26·9 (SD 23·9) mm Hg in the arteriovenous coupler group (p<0·0001) and by 3·7 (21·2) mm Hg in the control group (p=0·31). Mean systolic 24 h ambulatory blood pressure reduced by 13·5 (18·8) mm Hg (p<0·0001) in arteriovenous coupler recipients and by 0·5 (15·8) mm Hg (p=0·86) in controls. Implantation of the arteriovenous coupler was associated with late ipsilateral venous stenosis in 12 (29%) of 42 patients and was treatable with venoplasty or stenting.

INTERPRETATION

Arteriovenous anastomosis was associated with significantly reduced blood pressure and hypertensive complications. This approach might be a useful adjunctive therapy for patients with uncontrolled hypertension.

FUNDING

ROX Medical.

Predictors of blood pressure response in the SYMPLICITY HTN-3 trial

AIMS

The SYMPLICITY HTN-3 randomized, blinded, sham-controlled trial confirmed the safety of renal denervation (RDN), but did not meet its primary efficacy endpoint. Prior RDN studies have demonstrated significant and durable reductions in blood pressure. This analysis investigated factors that may help explain these disparate results.

METHODS AND RESULTS

Patients with resistant hypertension were randomized 2 : 1 to RDN (n = 364) or sham (n = 171). The primary endpoint was the difference in office systolic blood pressure (SBP) change at 6 months. A multivariable analysis identified predictors of SBP change. Additional analyses examined the influence of medication changes, results in selected subgroups and procedural factors. Between randomization and the 6-month endpoint, 39% of patients underwent medication changes. Predictors of office SBP reduction at 6 months were baseline office SBP ≥ 180 mmHg, aldosterone antagonist use, and non-use of vasodilators; number of ablations was a predictor in the RDN group. Non-African-American patients receiving RDN had a significantly greater change in office SBP than those receiving sham; -15.2 ± 23.5 vs. -8.6 ± 24.8 mmHg, respectively (P = 0.012). Greater reductions in office and ambulatory SBP, and heart rate were observed with a higher number of ablations and energy delivery in a four-quadrant pattern.

CONCLUSIONS

Post hoc analyses, although derived from limited patient cohorts, reveal several potential confounding factors that may partially explain the unexpected blood pressure responses in both the sham control and RDN groups. These hypothesis-generating data further inform the design of subsequent research to evaluate the potential role of RDN in the treatment of resistant hypertension. CLINICALTRIALS.GOV IDENTIFIER: NCT01418261.

Meta-analysis of the effect of renal denervation on blood pressure and pulse pressure in patients with resistant systemic hypertension

Data comparing the effect of renal denervation (RD) with those of maximal medical therapy (MMT) have shown conflicting results. Also, effect of RD on pulse pressure (PP) has not been evaluated. The aim of this meta-analysis was to compare the effect of RD with that of MMT on blood pressure (BP) and PP at 6-month follow-up in patients with resistant hypertension. Randomized controlled trials and nonrandomized controlled trials reporting systolic BP, diastolic BP, and PP results in RD and MMT groups at 6-month follow-up in patients with resistant hypertension were systematically reviewed, and eligible citations were pooled using a random-effects model. Five studies (3 randomized controlled trials, 2 nonrandomized controlled trials, n = 800) met the inclusion criteria. In the pooled analysis, RD was associated with a significant decrease in systolic BP (weighted mean difference -19.4 mm Hg, 95% confidence interval -32.8 to -5.9, p = 0.005), diastolic BP (weighted mean difference -6.4 mm Hg, 95% confidence interval -10.7 to -2.0 mm Hg, p = 0.004), and PP (weighted mean difference -12.7 mm Hg, 95% confidence interval -22.3 to -3.1 mm Hg, p = 0.009) compared with MMT at 6-month follow-up. Sensitivity analysis limited to randomized controlled trials showed a borderline significant difference in lowering systolic BP, a significant difference in lowering diastolic BP, and a nonsignificant difference in lowering PP when RD was compared with MMT. In conclusion, this meta-analysis shows that RD is superior to MMT in lowering BP, but heterogeneity among study populations in this pooled sample is high, and further data are needed to better compare these treatment strategies.

Expanding the indication spectrum: renal denervation in diabetes

Catheter-based renal denervation (RDN) has been shown to reduce sympathetic nerve activity and blood pressure in patients with resistant hypertension. Increased central sympathetic activity is a main contributor to the pathophysiology of several important chronic cardiovascular diseases, including diabetes and the metabolic syndrome. Indeed several recently published pilot studies and case reports suggest beneficial effects of RDN on glucose metabolism in patients with resistant hypertension. This review highlights the background of approaching the renal sympathetic nerves as a potential new therapeutic option to improve glycaemic control in patients with resistant hypertension.

Percutaneous renal denervation in patients with treatment-resistant hypertension: final 3-year report of the Symplicity HTN-1 study

BACKGROUND

Renal denervation (RDN) with radiofrequency ablation substantially reduces blood pressure in patients with treatment-resistant hypertension. We assessed the long-term antihypertensive effects and safety.

METHODS

Symplicity HTN-1 is an open-label study that enrolled 153 patients, of whom 111 consented to follow-up for 36 months. Eligible patients had a systolic blood pressure of at least 160 mm Hg and were taking at least three antihypertensive drugs, including a diuretic, at the optimum doses. Changes in office systolic blood pressure and safety were assessed every 6 months and reported every 12 months. This study is registered with ClinicalTrials.gov, numbers NCT00483808, NCT00664638, and NCT00753285.

FINDINGS

88 patients had complete data at 36 months. At baseline the mean age was 57 (SD 11) years, 37 (42%) patients were women, 25 (28%) had type 2 diabetes mellitus, the mean estimated glomerular filtration rate was 85 (SD 19) mL/min per 1·73 m(2), and mean blood pressure was 175/98 (SD 16/14) mm Hg. At 36 months significant changes were seen in systolic (-32·0 mm Hg, 95% CI -35·7 to -28·2) and diastolic blood pressure (-14·4 mm Hg, -16·9 to -11·9). Drops of 10 mm Hg or more in systolic blood pressure were seen in 69% of patients at 1 month, 81% at 6 months, 85% at 12 months, 83% at 24 months, and 93% at 36 months. One new renal artery stenosis requiring stenting and three deaths unrelated to RDN occurred during follow-up.

INTERPRETATION

Changes in blood pressure after RDN persist long term in patients with treatment-resistant hypertension, with good safety.

FUNDING

Ardian LLC/Medtronic Inc.

Chemohypersensitivity and autonomic modulation of venous capacitance in the pathophysiology of acute decompensated heart failure

Heart failure is increasing in prevalence around the world, with hospitalization and re-hospitalization as a result of acute decompensated heart failure (ADHF) presenting a huge social and economic burden. The mechanism for this decompensation is not clear. Whilst in some cases it is due to volume expansion, over half of patients with an acute admission for ADHF did not experience an increase in total body weight. This calls into question the current treatment strategy of targeting salt and water retention in ADHF. An alternative hypothesis proposed by Fallick et al. is that an endogenous fluid shift from the splanchnic bed is implicated in ADHF, rather than an exogenous fluid gain. The hypothesis states further that this shift is triggered by an increase in sympathetic tone causing vasoconstriction in the splanchnic bed, a mechanism that can translocate blood rapidly into the effective circulating volume, generating the raised venous pressure and congestion seen in ADHF. This hypothesis encourages a new clinical paradigm which focuses on the underlying mechanisms of congestion, and highlights the importance of fluid redistribution and neurohormonal activation in its pathophysiology. In this article, we consider the concept that ADHF is attributable to episodic sympathetic hyperactivity, resulting in fluid shifts from the splanchnic bed. Chemosensitivity is a pathologic autonomic mechanism associated with mortality in patients with systolic heart failure. Tonic and episodic activity of the peripheral chemoreceptors may underlie the syndrome of acute decompensation without total body salt and water expansion. We suggest in this manuscript that chemosensitivity in response to intermittent hypoxia, such as experienced in sleep disordered breathing, may explain the intermittent sympathetic hyperactivity underlying renal sodium retention and acute volume redistribution from venous storage sites. This hypothesis provides an alternative structure to guide novel diagnostic and treatment strategies for ADHF.

Dissociation between blood pressure and heart rate response to hypoxia after bilateral carotid body removal in men with systolic heart failure

While the ventilatory response to hypoxia is known to be mediated by the carotid bodies, the origin of the haemodynamic alterations evoked by hypoxia is less certain. Bilateral carotid body removal (CBR) performed to treat congestive heart failure may serve as a model to improve our understanding of haemodynamic responses to hypoxia in humans. We studied six congestive heart failure patients before and 1 month after CBR [median (interquartile range): age, 58.5 (56-61) years old; and ejection fraction, 32 (25-34)%]. Peripheral chemosensitivity (hypoxic ventilatory response) was equated to the slope relating lowest oxygen saturation to highest minute ventilation following exposures to hypoxia. Likewise, systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) slopes were calculated as slopes relating the lowest oxygen saturations to the highest SBP, DBP and HR responses. We found that CBR reduces the hypoxic ventilatory response (91%, P < 0.05), SBP (71%, P < 0.05) and DBP slopes (59%, P = 0.07). In contrast, the HR slope remained unchanged. The dissociation between the blood pressure and HR responses after CBR shows involvement of a different chemoreceptive site(s) maintaining the response to acute hypoxia. We conclude that carotid bodies are responsible for ventilatory and blood pressure responses, while the HR response might be mediated by the aortic bodies. The significant reduction of the blood pressure response to hypoxia after CBR suggests a decrease in sympathetic tone, which is of particular clinical relevance in congestive heart failure.

International expert consensus statement: Percutaneous transluminal renal denervation for the treatment of resistant hypertension

Catheter-based radiofrequency ablation technology to disrupt both efferent and afferent renal nerves has recently been introduced to clinical medicine after the demonstration of significant systolic and diastolic blood pressure reductions. Clinical trial data available thus far have been obtained primarily in patients with resistant hypertension, defined as standardized systolic clinic blood pressure ≥ 160 mm Hg (or ≥ 150 mm Hg in patients with type 2 diabetes) despite appropriate pharmacologic treatment with at least 3 antihypertensive drugs, including a diuretic agent. Accordingly, these criteria and blood pressure thresholds should be borne in mind when selecting patients for renal nerve ablation. Secondary forms of hypertension and pseudoresistance, such as nonadherence to medication, intolerance of medication, and white coat hypertension, should have been ruled out, and 24-h ambulatory blood pressure monitoring is mandatory in this context. Because there are theoretical concerns with regard to renal safety, selected patients should have preserved renal function, with an estimated glomerular filtration rate ≥ 45 ml/min/1.73 m(2). Optimal periprocedural management of volume status and medication regimens at specialized and experienced centers equipped with adequate infrastructure to cope with potential procedural complications will minimize potential patient risks. Long-term safety and efficacy data are limited to 3 years of follow-up in small patient cohorts, so efforts to monitor treated patients are crucial to define the long-term performance of the procedure. Although renal nerve ablation could have beneficial effects in other conditions characterized by elevated renal sympathetic nerve activity, its potential use for such indications should currently be limited to formal research studies of its safety and efficacy.

Revelations about carotid body function through its pathological role in resistant hypertension

Much recent attention has been given to the carotid body because of its potential role in cardiovascular disease states. One disease, neurogenic hypertension, characterised by excessive sympathetic activity, appears dependent on carotid body activity that may or may not be accompanied by sleep-disordered breathing. Herein, we review recent literature suggesting that the carotid body acquires tonicity in hypertension. We predict that carotid glomectomy will be a powerful way to temper excessive sympathetic discharge in diseases such as hypertension. We propose a model to explain that signalling from the 'hypertensive' carotid body is tonic, and hypothesise that there will be a sub-population of glomus cells that channel separately into reflex pathways controlling sympathetic motor outflows.

Ambulatory blood pressure changes after renal sympathetic denervation in patients with resistant hypertension

BACKGROUND

Catheter-based renal sympathetic denervation (RDN) reduces office blood pressure (BP) in patients with resistant hypertension according to office BP. Less is known about the effect of RDN on 24-hour BP measured by ambulatory BP monitoring and correlates of response in individuals with true or pseudoresistant hypertension.

METHODS AND RESULTS

A total of 346 uncontrolled hypertensive patients, separated according to daytime ambulatory BP monitoring into 303 with true resistant (office systolic BP [SBP] 172.2±22 mm Hg; 24-hour SBP 154±16.2 mm Hg) and 43 with pseudoresistant hypertension (office SBP 161.2±20.3 mm Hg; 24-hour SBP 121.1±19.6 mm Hg), from 10 centers were studied. At 3, 6, and 12 months follow-up, office SBP was reduced by 21.5/23.7/27.3 mm Hg, office diastolic BP by 8.9/9.5/11.7 mm Hg, and pulse pressure by 13.4/14.2/14.9 mm Hg (n=245/236/90; P for all <0.001), respectively. In patients with true treatment resistance there was a significant reduction with RDN in 24-hour SBP (-10.1/-10.2/-11.7 mm Hg, P<0.001), diastolic BP (-4.8/-4.9/-7.4 mm Hg, P<0.001), maximum SBP (-11.7/-10.0/-6.1 mm Hg, P<0.001) and minimum SBP (-6.0/-9.4/-13.1 mm Hg, P<0.001) at 3, 6, and 12 months, respectively. There was no effect on ambulatory BP monitoring in pseudoresistant patients, whereas office BP was reduced to a similar extent. RDN was equally effective in reducing BP in different subgroups of patients. Office SBP at baseline was the only independent correlate of BP response.

CONCLUSIONS

RDN reduced office BP and improved relevant aspects of ambulatory BP monitoring, commonly linked to high cardiovascular risk, in patients with true-treatment resistant hypertension, whereas it only affected office BP in pseudoresistant hypertension.

Denervation (ablation) of nerve terminalis in renal arteries: early results of interventional treatment of arterial hypertension in Poland

BACKGROUND

Arterial hypertension is one of the main causes of cardiovascular disease morbidity and overall mortality.

AIM

To report the single centre experiences with changes in arterial blood pressure (BP) in patients after intra-arterial application of radiofrequency (RF) energy to cause renal sympathetic efferent and somatic afferent nerve and report vascular and kidney safety in a six month follow up.

METHODS

Twenty-eight patients, with hypertension despite medical therapy (median age 52.02 years, range 42-72 years) consented to therapeutic renal nerve ablation. SIMPLICITY RF catheters and generator provided by Ardian (currently Medtronic Inc., USA) were used to perform renal artery angiography and ablation.

RESULTS

The mean BP at baseline, and after one month, three months and six months were measured [mm Hg]: systolic 176.6; 162.3 (p = 0.004); 150.6 (p < 0.001); 147.2 (p < 0.001); diastolic 100.2; 90.3 (p < 0.001); 91.79 (p = 0.03); 88.5 (p < 0.001); pulse pressure 76.57; 75.18 (p = NS); 65.80 (p < 0.001); 62.15 (p < 0.001). Neither procedure-related nor therapy-related complications were reported in the six month follow up.

CONCLUSIONS

In our cohort of patients, intra-arterial renal nerve denervation was not associated with either vascular or renal complications out to six months. Nerve ablation of renal arteries led to significant reduction of mean values of arterial systolic, diastolic BP and significant reduction of pulse pressure. The Polish experience is not significantly different compared to that reported in the Symplicity I and Symplicity II international cohorts. The long term durability of this therapy and its application to earlier stages of hypertension or other disease states will require further investigation.

Vascular and renal hemodynamic changes after renal denervation

BACKGROUND AND OBJECTIVES

Renal denervation (RDN) has been shown to be effective in reducing BP in treatment-resistant hypertension. Measurement of the renal and sympathetic activity revealed a decrease in sympathetic drive to the kidney and small resistance vessels after RDN. However, the consequences on renal perfusion and renal vascular resistance (RVR), as well as central hemodynamics, are unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Nineteen patients with treatment-resistant hypertension (office BP≥140/90 mmHg, despite at least three antihypertensive drugs [including a diuretic], and diagnosis confirmed by 24-hour ambulatory BP monitoring) underwent RDN between January and October 2011. Renal perfusion and RVR were noninvasively assessed by magnetic resonance imaging with arterial spin labeling, and renal function was assessed by estimating GFR before (day -1), after (day +1), and again after 3 months of RDN. Central hemodynamics was assessed using pulse wave analysis at day -1 and after 6 months of RDN.

RESULTS

Peripheral office BP (systolic, 158±26 versus 142±23 mmHg, P=0.002; diastolic, 83±13 versus 76±9 mmHg, P=0.02) and mean systolic 24-hour ambulatory BP (159±17 versus 152±17 mmHg, P=0.02) were significantly reduced 6 months after RDN. Renal perfusion was not statistically different between day -1 and day +1 (256.8 [interquartile range (IQR), 241-278] versus 263.4 [IQR, 252-277] ml/min per 100 g; P=0.17) as well as after 3 months (256.8 [IQR, 241-278] versus 261.2 [IQR, 240-285] ml/min per 100 g; P=0.27) after RDN. RVR dropped (432.1 [IQR, 359-525] versus 390.6 [IQR, 338-461] AU; P=0.02), whereas renal function was not statistically different at any time point. Central systolic BP (145±31 versus 131±28 mmHg; P=0.009), diastolic BP (85±18 versus 80±14 mmHg; P=0.03), and central pulse pressure (61±18 versus 52±18 mmHg; P=0.02) were significantly reduced 6 months after RDN. Central augmentation index (24±8 versus 20±8%; P=0.02) was decreased 6 months after RDN.

CONCLUSION

The data indicate that RDN significantly reduced peripheral and central BP. Despite reduced systemic BP, renal perfusion and function did not change after RDN.

Carotid body removal for treatment of chronic systolic heart failure

BACKGROUND

Augmented reflex response from peripheral chemoreceptors characterises chronic heart failure (CHF), contributes to autonomic imbalance and exercise intolerance and predicts poor outcome.

METHODS AND RESULTS

We present a case of a 56-year-old male patient with ischaemic CHF, who underwent surgical, unilateral carotid body resection to reduce peripheral chemosensitivity. At 2-month and 6-month follow-ups, we document a persistent decrease in peripheral chemosensitivity accompanied by an improvement in exercise capacity, sleep disordered breathing and quality of life. Autonomic balance was favourably affected as evidenced by improved heart rate variability and augmented cardiac baroreflex sensitivity. There were no procedure-related adverse events.

CONCLUSIONS

Denervation of a carotid body may offer a clinical strategy to restore autonomic balance and improve morbidity in heart failure (NCT01653821).

Renal sympathetic denervation for treatment of drug-resistant hypertension: one-year results from the Symplicity HTN-2 randomized, controlled trial

BACKGROUND

Renal sympathetic nerve activation contributes to the pathogenesis of hypertension. Symplicity HTN-2, a multicenter, randomized trial, demonstrated that catheter-based renal denervation produced significant blood pressure lowering in treatment-resistant patients at 6 months after the procedure compared with control, medication-only patients. Longer-term follow-up, including 6-month crossover results, is now presented.

METHODS AND RESULTS

Eligible patients were on ≥3 antihypertensive drugs and had a baseline systolic blood pressure ≥160 mm Hg (≥150 mm Hg for type 2 diabetics). After the 6-month primary end point was met, renal denervation in control patients was permitted. One-year results on patients randomized to immediate renal denervation (n=47) and 6-month postprocedure results for crossover patients are presented. At 12 months after the procedure, the mean fall in office systolic blood pressure in the initial renal denervation group (-28.1 mm Hg; 95% confidence interval, -35.4 to -20.7; P<0.001) was similar to the 6-month fall (-31.7 mm Hg; 95% confidence interval, -38.3 to -25.0; P=0.16 versus 6-month change). The mean systolic blood pressure of the crossover group 6 months after the procedure was significantly lowered (from 190.0±19.6 to 166.3±24.7 mm Hg; change, -23.7±27.5; P<0.001). In the crossover group, there was 1 renal artery dissection during guide catheter insertion, before denervation, corrected by renal artery stenting, and 1 hypotensive episode, which resolved with medication adjustment.

CONCLUSIONS

Control patients who crossed over to renal denervation with the Symplicity system had a significant drop in blood pressure similar to that observed in patients receiving immediate denervation. Renal denervation provides safe and sustained reduction of blood pressure to 1 year.

Feasibility of catheter-based renal nerve ablation and effects on sympathetic nerve activity and blood pressure in patients with end-stage renal disease

BACKGROUND AND OBJECTIVES

Sympathetic activation is a hallmark of ESRD and adversely affects cardiovascular prognosis. Efferent sympathetic outflow and afferent neural signalling from the failing native kidneys are key mediators and can be targeted by renal denervation (RDN). Whether this is feasible and effective in ESRD is not known.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

In an initial safety and proof-of-concept study we attempted to perform RDN in 12 patients with ESRD and uncontrolled blood pressure (BP). Standardized BP measurements were obtained in all patients on dialysis free days at baseline and follow up. Measures of renal noradrenaline spillover and muscle sympathetic nerve activity were available from 5 patients at baseline and from 2 patients at 12 month follow up and beyond.

RESULTS

Average office BP was 170.8 ± 16.9/89.2 ± 12.1 mmHg despite the use of 3.8 ± 1.4 antihypertensive drugs. All 5 patients in whom muscle sympathetic nerve activity and noradrenaline spillover was assessed at baseline displayed substantially elevated levels. Three out of 12 patients could not undergo RDN due to atrophic renal arteries. Compared to baseline, office systolic BP was significantly reduced at 3, 6, and 12 months after RDN (from 166 ± 16.0 to 148 ± 11, 150 ± 14, and 138 ± 17 mmHg, respectively), whereas no change was evident in the 3 non-treated patients. Sympathetic nerve activity was substantially reduced in 2 patients who underwent repeat assessment.

CONCLUSIONS

RDN is feasible in patients with ESRD and associated with a sustained reduction in systolic office BP. Atrophic renal arteries may pose a problem for application of this technology in some patients with ESRD.

The carotid body as a putative therapeutic target for the treatment of neurogenic hypertension

In the spontaneously hypertensive (SH) rat, hyperoxic inactivation of the carotid body (CB) produces a rapid and pronounced fall in both arterial pressure and renal sympathetic nerve activity (RSA). Here we show that CB de-afferentation through carotid sinus nerve denervation (CSD) reduces the overactive sympathetic activity in SH rats, providing an effective antihypertensive treatment. We demonstrate that CSD lowers RSA chronically and that this is accompanied by a depressor response in SH but not normotensive rats. The drop in blood pressure is not dependent on renal nerve integrity but mechanistically accompanied by a resetting of the RSA-baroreflex function curve, sensitization of the cardiac baroreflex, changes in renal excretory function and reduced T-lymphocyte infiltration. We further show that combined with renal denervation, CSD remains effective, producing a summative response indicative of an independent mechanism. Our findings indicate that CB de-afferentation is an effective means for robust and sustained sympathoinhibition, which could translate to patients with neurogenic hypertension.