Barorezeptorakivierungstherapie bei therapierefraktärer Hypertonie: Indikation und Patientenselektion: Empfehlungen der BAT-Konsensusgruppe 2017

Effect of baroreflex activation therapy on dipping pattern in patients with resistant hypertension

A relevant number of patients with resistant hypertension do not achieve blood pressure (BP) dipping during nighttime. This inadequate nocturnal BP reduction is associated with elevated cardiovascular risks. The aim of this study was to evaluate whether a nighttime intensification of BAT might improve nocturnal BP dipping. In this prospective observational study, non-dippers treated with BAT for at least 6 months were included. BAT programming was modified in a two-step intensification of nighttime stimulation at baseline and week 6. Twenty-four hours ambulatory BP (ABP) was measured at inclusion and after 3 months. A number of 24 patients with non- or inverted dipping pattern, treated with BAT for a median of 44 months (IQR 25-52) were included. At baseline of the study, patients were 66 ± 9 years old, had a BMI of 33 ± 6 kg/m² , showed an office BP of 135 ± 22/72 ± 10 mmHg, and took a median number of antihypertensives of 6 (IQR 4-9). Nighttime stimulation of BAT was adapted by an intensification of pulse width from 237 ± 161 to 267 ± 170 μs (p = .003) while frequency (p = .10) and amplitude (p = .95) remained unchanged. Uptitration of BAT programming resulted in an increase of systolic dipping from 2 ± 6 to 6 ± 8% (p = .03) accompanied with a significant improvement of dipping pattern (p = .02). Twenty four hours ABP, day- and nighttime ABP remained unchanged. Programming of an intensified nighttime BAT interval improved dipping profile in patients treated with BAT, while the overall 24 h ABP did not change. Whether the improved dipping response contributes to a reduction of cardiovascular risk beyond the BP-lowering effects of BAT, however, remains to be shown.

Impact of medication adherence on the efficacy of Baroreflex activation therapy

Therapy adherence significantly determines the success of antihypertensive therapy, especially in patients with resistant hypertension. Our study investigates the impact of drug adherence on the efficacy of Baroreflex‐activation‐therapy (BAT). In this retrospective analysis, the authors measured blood pressure (BP) and antihypertensive medication adherence (by gas chromatography‐mass spectrometry [GC‐MS] urine analysis) before and 6 months after BAT initiation. Adherence was defined as detection of ≥80% intake of prescribed medication at the time of follow‐up. Response to BAT was defined as BP drop ≥5 mmHg in systolic 24 h‐ambulatory BP (ABP) after 6 months. Overall patients (n = 38) median medication adherence was low, but rose from 60% (IQR 25%–100%) to 75% (IQR 38%–100%; p = .0194). After 6 months of BAT, mean systolic and diastolic office BP (‐21 ± 25 mmHg and ‐9 ± 15 mmHg; p < .0001 and .0004) as well as 24 h‐ABP dropped significantly (‐9 ± 17 mmHg and ‐5 ± 12 mmHg; p = .0049 and .0280). After 6 months of BAT, 21 patients (60%) could be classified as responders. There was neither significant difference in mean office systolic (‐21 ± 23 mmHg vs. ‐21 ± 28 mmHg; p = .9581) nor in 24 h‐systolic ABP decrease (‐11 ± 19 mmHg vs. ‐7 ± 15 mmHg; p = .4450) comparing adherent and non‐adherent patients. Whereas Antihypertensive Therapeutic Index (ATI) was unchanged in non‐responders, it significantly decreased in responders (from 50 ± 16 to 46 ± 16; p = .0477). These data are the first to show that BAT‐initiation leads to a clear BP reduction independently of patients´ medication adherence. Response to BAT is associated with a significant lowering of ATI, which might contribute to an underestimation of BAT efficacy.

Eligibility for Baroreflex Activation Therapy and medication adherence in patients with apparently resistant hypertension

Uncontrolled hypertension is a main risk factor for cardiovascular morbidity. Baroreflex activation therapy (BAT) is an effective therapy option addressing true resistant hypertension. We evaluated patients’ eligibility for BAT in a staged assessment as well as adherence to antihypertensive drug therapy. Therefore, we analyzed files of 345 patients, attending the hypertension clinic at University Medicine Göttingen. Additionally, gas chromatographic‐mass spectrometric urine analyses of selected individuals were performed evaluating their adherence. Most common cause for a revoked BAT recommendation was blood pressure (BP) control by drug adjustment (54.2%). Second leading cause was presence of secondary hypertension (31.6%). Patients to whom BAT was recommended (59 (17.1%)) were significantly more often male (67.8% vs. 43.3%, P = .0063), had a higher body mass index (31.8 ± 5.8 vs. 30.0 ± 5.7 kg/m², P = .0436), a higher systolic office (168.7 ± 24.7 vs. 147.7 ± 24.1 mmHg, P < .0001), and 24h ambulatory BP (155.0 ± 14.6 vs. 144.4 ± 16.8 mmHg, P = .0031), took more antihypertensive drugs (5.8 ± 1.3 vs. 4.4 ± 1.4, P < .0001), and suffered more often from numerous concomitant diseases. Eventually, 27 (7.8%) received a BAT system. In the toxicological analysis of 75 patients, mean adherence was 75.1%. 16 patients (21.3%) showed non‐adherence. Thus, only a small number of patients eventually received a BAT system, as treatable reasons for apparently resistant hypertension could be identified frequently. This study is—to our knowledge—the first report of a staged assessment of patients’ suitability for BAT and underlines the need for a careful examination and indication. Non‐adherence was proven to be a relevant issue concerning apparently resistant hypertension and therefore non‐eligibility for interventional antihypertensive therapy.

We evaluated the eligibility for baroreflex activation therapy (BAT) of 345 patients, attending the hypertension clinic at University Medicine Göttingen. Patients’ drug adherence was investigated by 75 toxicological analyses. Most common cause for a revoked BAT recommendation was blood pressure control by drug adjustment. Eventually, only less patients (7.8%) received a BAT system. Patients receiving a BAT recommendation showed specific characteristics and suffered numerous comorbidities, leading to a high cardiovascular risk, and therefore seem to greatly benefit from BAT implantation. 21.3% of patients showed non‐adherence, proving non‐adherence to be a relevant issue.

Implant-Mediated Therapy of Arterial Hypertension

PURPOSE OF REVIEW

To give an overview on recent developments in permanent implant-based therapy of resistant hypertension.

RECENT FINDINGS

The American Heart Association (AHA) recently updated their guidelines to treat high blood pressure (BP). As elevated BP now is defined as a systolic BP above 120 mmHg, the prevalence of hypertension in the USA has increased from 32% (old definition of hypertension) to 46%. In the past years, device- and implant-mediated therapies have evolved and extensively studied in various patient populations. Despite an initial drawback in a randomized controlled trial (RCT) of bilateral carotid sinus stimulation (CSS), new and less invasive and unilateral systems for baroreflex activation therapy (BAT) with the BAROSTIM NEO® have been developed which show promising results in small non-randomized controlled (RCT) studies. Selective vagal nerve stimulation (VNS) has been successfully evaluated in rodents, but has not yet been tested in humans. A new endovascular approach to reshape the carotid sinus to lower BP (MobiusHD™) has been introduced (baroreflex amplification therapy) with favorable results in non-RCT trials. However, long-term results are not yet available for this treatment option. A specific subgroup of patients, those with indication for a 2-chamber cardiac pacemaker, may benefit from a new stimulation paradigm which reduces the AV latency and therefore limits the filling time of the left ventricle. The most invasive approach for resistant hypertension still is the neuromodulation by deep brain stimulation (DBS), which has been shown to significantly lower BP in single cases. Implant-mediated therapy remains a promising approach for the treatment of resistant hypertension. Due to their invasiveness, such treatment options must prove superiority over conventional therapies with regard to safety and efficacy before they can be generally offered to a wider patient population. Overall, BAROSTIM NEO® and MobiusHD™, for which large RCTs will soon be available, are likely to meet those criteria and may represent the first implant-mediated therapeutical options for hypertension, while the use of DBS probably will be reserved for individual cases. The utility of VNS awaits appropriate assessment.

Testing individual baroreflex responses to hypoxia-induced peripheral chemoreflex stimulation

Introduction

Baroreflexes and peripheral chemoreflexes control efferent autonomic activity making these reflexes treatment targets for arterial hypertension. The literature on their interaction is controversial, with suggestions that their individual and collective influence on blood pressure and heart rate regulation is variable. Therefore, we applied a study design that allows the elucidation of individual baroreflex–chemoreflex interactions.

Methods

We studied nine healthy young men who breathed either normal air (normoxia) or an air–nitrogen–carbon dioxide mixture with decreased oxygen content (hypoxia) for 90 min, with randomization to condition, followed by a 30-min recovery period and then exposure to the other condition for 90 min. Multiple intravenous phenylephrine bolus doses were applied per condition to determine phenylephrine pressor sensitivity as an estimate of baroreflex blood pressure buffering and cardiovagal baroreflex sensitivity (BRS).

Results

Hypoxia reduced arterial oxygen saturation from 98.1 ± 0.4 to 81.0 ± 0.4% (p < 0.001), raised heart rate from 62.9 ± 2.1 to 76.0 ± 3.6 bpm (p < 0.001), but did not change systolic blood pressure (p = 0.182). Of the nine subjects, six had significantly lower BRS in hypoxia (p < 0.05), two showed a significantly decreased pressor response, and three showed a significantly increased pressor response to phenylephrine in hypoxia, likely through reduced baroreflex buffering (p < 0.05). On average, hypoxia decreased BRS by 6.4 ± 0.9 ms/mmHg (19.9 ± 2.0 vs. 14.12 ± 1.6 ms/mmHg; p < 0.001) but did not change the phenylephrine pressor response (p = 0.878).

Conclusion

We applied an approach to assess individual baroreflex–chemoreflex interactions in human subjects. A subgroup exhibited significant impairments in baroreflex blood pressure buffering and BRS with peripheral chemoreflex activation. The methodology may have utility in elucidating individual pathophysiology and in targeting treatments modulating baroreflex or chemoreflex function.

Kidney protective effects of baroreflex activation therapy in patients with resistant hypertension

Baroreflex activation therapy (BAT) is approved for the treatment of resistant hypertension. In addition to blood pressure (BP) reduction, pilot studies suggested several organoprotective effects of BAT. Thirty-two patients with resistant hypertension were prospectively treated with BAT. Besides office BP and 24-hour ambulatory BP (ABP) measurements, detection of a urinary proteome-based classifier (CKD273), which has been shown to predict chronic kidney disease (CKD) progression, was carried out at baseline and after 6 months of BAT. Office BP significantly decreased from 170 ± 25/90 ± 18 to 149 ± 29/82 ± 18 mm Hg. Analysis of CKD273 score and eGFR with CKD-EPI equation at baseline revealed strong correlation (r = 0.568, P < 0.001). After 6 months of BAT, there was no significant change in CKD273 score (-0.061 [95% CI: -0.262 to 0.140], P = 0.601). However, by stratification of the data regarding ABP response, there was a statistically significant (P = 0.0113) reduction in the CKD273 score from a mean of 0.161 [95% CI: -0.093 to 0.414] to -0.346 [95% CI: -0.632 to -0.060] after BAT in patients with systolic ABP decrease of ≥5 mm Hg. These data emphasized potential nephroprotective effects of BAT in patients with sufficient BP response.