Effect Baroreflex Activation Therapy on the Carotid Body

Study Overview
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Brief Summary
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Carotid baroreflex activation therapy (BAT) by the Rheos® system produces a sustained fall in blood pressure in patients with resistant hypertension. Since the activation electrodes are implanted at the level of the carotid sinus, it is conceivable that the nearby located carotid body chemoreceptors are stimulated as well. Physiological stimulation of carotid chemoreceptors not only raises respiration, but it also increases sympathetic activity which may in part counteract the effects of BAT. The aim of the present study is to investigate whether there is evidence for concomitant carotid chemoreflex activation during BAT. We hypothesized that there is no clinically relevant co-activation of the carotid body chemoreceptors during BAT in patients with resistant hypertension.

Official Title
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Carotid Baroreflex Activation and Its Effect on the Chemoreflex Study

Conditions
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Hypertension Resistant To Conventional Therapy, Baroreflex, Carotid Body

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Be currently implanted with Rheos system and have completed the 13-month follow-up period. Be on stable anti-hypertensive therapy for at least 4 weeks prior to inclusion, where stable is defined as no changes in medications or dosage of medications. Have at least one functional carotid baroreflex activation electrode. Have signed and approved informed consent form for participation in this study. Exclusion Criteria: Myocardial infarction (MI) or cerebral vascular accident (CVA) within the past 90 days, or subject is still unstable from a prior MI or CVA that occurred more than 90 days ago. Are unable or unwilling to comply with the protocol requirements of this study. Diagnosed with severe chronic obstructive lung disease (COPD/asthma GOLD stadium III and IV).

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Resistant hypertensive patients with Rheos system<br>We will program 6 electrical device activation setting twice in a random order to see what happens with the aforementioned respiratory and cardiovascular variables. The following electrical settings will be programmed for 4 minutes each setting: 20 Hz, 3 Volts, 480 microseconds 20 Hz, 6 Volts, 480 microseconds 50 Hz, 3 Volts, 480 microseconds 50 Hz, 6 Volts, 480 microseconds 90 Hz, 3 Volts, 480 microseconds 90 Hz, 6 Volts, 480 microseconds | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in arterial CO2 (PaCO2) during baroreflex activation therapy | During one hour several device activation settings will be programmed at random. During each device setting we will collect arterial blood samples to check for PaCO2. | 6 times during different electrical activation settings within one hour | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in end-tidal CO2 during baroreflex activation therapy | Change in respiratory variables will be analyzed during the aforementioned time frame in which we will program several device activation settings. | 1 - 1.25 hour | 
| Change in blood pressure during baroreflex activation therapy | The change in cardiovascular variables will be analyzed during each device activation setting | 1 - 1.25 hour | 
| Change in respiratory rate during baroreflex activation therapy | Change in respiratory variables will be analyzed during the aforementioned time frame in which we will program several device activation settings. | 1 - 1.25 hour | 
| Change in expiration time during baroreflex activation therapy | Change in respiratory variables will be analyzed during the aforementioned time frame in which we will program several device activation settings. | 1 - 1.25 hour | 
| Change in heart rate during baroreflex activation therapy | The change in cardiovascular variables will be analyzed during each device activation setting | 1 - 1.25 hour | 
| Change in peripheral vascular resistance during baroreflex activation therapy | The change in cardiovascular variables will be analyzed during each device activation setting | 1 - 1.25 hour | 
| Change in forced expiratory volume-1 second (FEV1) before and after turning off the device |  | 2 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Baroreflex, Electrical stimulation, Carotid body, Chemoreceptors, Resistant hypertension