Baroreflex activation for the treatment of hypertension: principles and practice

Baroreceptors in the carotid and hypertension-systematic review and meta-analysis of the effects of baroreflex activation therapy on blood pressure

Activation of baroreceptors in the carotid modulates the autonomic nervous system. Baroreflex activation therapy (BAT), which activates baroreceptors in the carotid, has become available in the treatment of resistant hypertension. Besides this, a carotid implant modulating baroreceptors as well as pharmacological modulation of carotid bodies were quite recently presented. This review will underscore currently available and promising approaches that activate baroreceptors in the carotid, and thereby contribute to beneficial effects in patients with arterial hypertension, and discusses potential organoprotective BAT effects beyond blood pressure (BP) reduction. A systematic review and meta-analysis was conducted including observational studies or randomized controlled trials that investigated the effect of BAT on BP in resistant hypertension. Nine studies, seven observational and two randomized, with a total of 444 patients, were included in the evaluation. Analysing the longest follow-up visit from the different studies, there was a significant reduction of systolic BP after BAT of -36 mmHg [95% confidence interval (CI) -42 to -30 mmHg]. Separate meta-analysis of the short-term (1-6 months) and long-term effects (≥12 months) revealed a reduction of -21 mmHg (95% CI -26 to -17 mmHg) and -38 mmHg (95% CI -46 to -30 mmHg), respectively. There are promising data both in the experimental and the clinical application for BAT. Though the present meta-analysis suggests beneficial effects of BAT on BP, the results must be interpreted extremely carefully. Considering that evidence from controlled trials is very limited, it is evident that there is a strong need for further investigation.

Effects of the Right Carotid Sinus Compression Technique on Blood Pressure and Heart Rate in Medicated Patients with Hypertension

OBJECTIVES

To identify the immediate and middle-term effects of the right carotid sinus compression technique on blood pressure and heart rate in hypertensive patients.

DESIGN

Randomized blinded experimental study.

SETTINGS

Primary health centers of Cáceres (Spain).

SUBJECTS

Sixty-four medicated patients with hypertension were randomly assigned to an intervention group (n = 33) or to a control group (n = 31).

INTERVENTION

In the intervention group a compression of the right carotid sinus was applied for 20 sec. In the control group, a placebo technique of placing hands on the radial styloid processes was performed.

OUTCOME MEASURES

Blood pressure and heart rate were measured in both groups before the intervention (preintervention), immediately after the intervention, 5 min after the intervention, and 60 min after the intervention.

RESULTS

The intervention group significantly decreased systolic and diastolic blood pressure and heart rate immediately after the intervention, with a large clinical effect; systolic blood pressure remained reduced 5 min after the intervention, and heart rate remained reduced 60 min after the intervention. No significant changes were observed in the control group.

CONCLUSIONS

Right carotid sinus compression could be clinically useful for regulating acute hypertension.

Neural modulation for hypertension and heart failure

Hypertension (HTN) and heart failure (HF) have a significant global impact on health, and lead to increased morbidity and mortality. Despite recent advances in pharmacologic and device therapy for these conditions, there is a need for additional treatment modalities. Patients with sub-optimally treated HTN have increased risk for stroke, renal failure and heart failure. The outcome of HF patients remains poor despite modern pharmacological therapy and with established device therapies such as CRT and ICDs. Therefore, the potential role of neuromodulation via renal denervation, baro-reflex modulation and vagal stimulation for the treatment of resistant HTN and HF is being explored. In this manuscript, we review current evidence for neuromodulation in relation to established drug and device therapies and how these therapies may be synergistic in achieving therapy goals in patients with treatment resistant HTN and heart failure. We describe lessons learned from recent neuromodulation trials and outline strategies to improve the potential for success in future trials. This review is based on discussions between scientists, clinical trialists, and regulatory representatives at the 11th annual CardioVascular Clinical Trialist Forum in Washington, DC on December 5-7, 2014.

Therapeutic perspectives in hypertension: novel means for renin-angiotensin-aldosterone system modulation and emerging device-based approaches

The conventional antihypertensive therapies including renin–angiotensin–aldosterone system antagonists (converting enzyme inhibitors, receptor blockers, renin inhibitors, and mineralocorticoid receptor blockers), diuretics, β-blockers, and calcium channel blockers are variably successful in achieving the challenging target blood pressure values in hypertensive patients. Difficult to treat hypertension is still a commonly observed problem world-wide. A number of drugs are considered to be used as novel therapies for hypertension. Renalase supplementation, vasopeptidase inhibitors, endothelin antagonists, and especially aldosterone antagonists (aldosterone synthase inhibitors and novel selective mineralocorticoid receptor blockers) are considered an option in resistant hypertension. In addition, the aldosterone antagonists as well as (pro)renin receptor blockers or AT₂ receptor agonists might attenuate end-organ damage. This array of medications has now been complemented by a number of new approaches of non-pharmacological strategies including vaccination, genomic interference, controlled breathing, baroreflex activation, and probably most successfully renal denervation techniques. However, the progress on innovative therapies seems to be slow and the problem of resistant hypertension and proper blood pressure control appears to be still persisting. Therefore the regimens of currently available drugs are being fine-tuned, resulting in the establishment of several novel fixed-dose combinations including triple combinations with the aim to facilitate proper blood pressure control. It remains an exciting question which approach will confer the best blood pressure control and risk reduction in this tricky disease.

Carotid baroreceptor stimulation for the treatment of resistant hypertension

Interventional activation of the carotid baroreflex has been an appealing idea for the management of resistant hypertension for several decades, yet its clinical application remained elusive and a goal for the future. It is only recently that the profound understanding of the complex anatomy and pathophysiology of the circuit, combined with the accumulation of relevant experimental and clinical data both in animals and in humans, has allowed the development of a more effective and well-promising approach. Indeed, current data support a sustained over a transient reduction of blood pressure through the resetting of baroreceptors, and technical deficits have been minimized with a subsequent recession of adverse events. In addition, clinical outcomes from the application of a new implantable device (Rheos) that induces carotid baroreceptor stimulation point towards a safe and effective blood pressure reduction, but longer experience is needed before its integration in the everyday clinical practice. While accumulating evidence indicates that carotid baroreceptor stimulation exerts its benefits beyond blood pressure reduction, further research is necessary to assess the spectrum of beneficial effects and evaluate potential hazards, before the extraction of secure conclusions.

Beyond conventional considerations: newer devices used in blood pressure measurement and management

Several noninvasive devices are now available to assess blood vessel structure and function and have been shown in longitudinal cohort studies to provide additional cardiovascular event prediction over that obtained by conventional brachial blood pressure (BP) measurements. Among these newer measurements are estimates of vascular stiffness (as determined by the pulse wave velocity in the aorta) and measures of pulse wave reflection. Pulse wave velocity, in particular, has been well studied in end-stage kidney (ESKD) populations where it predicts cardiovascular events and death independently of standard BP. In addition, there are minimum 3 devices, either marketed or used in clinical trials, that are useful in some clinical situations as an adjunct to drug therapy for managing high BP. This review will focus on the roles of these new technologies in evaluating and managing high BP, emphasizing the CKD/ESKD patient where possible, although data are limited in the kidney disease population when it comes to managing BP with these novel device approaches.

Mechanisms of blood pressure reduction by prolonged activation of the baroreflex

Recent technological advances have made the activation of the afferent limb of the baroreflex a viable therapeutic approach for lowering blood pressure. Experimental studies demonstrate sustained reductions in blood pressure in response to electrical baroreflex activation and initial results from clinical trials using device-based therapy for drug-resistant hypertension are promising. Although theoretically obvious at first glance, the mechanisms involved in the blood pressure lowering effect of baroreflex activation elude precise quantification, and experiments designed to investigate them invariably challenge preconceived notions and even dogmas. This paper is a brief overview of our current understanding of these mechanisms.