title: Systemic vascular effects of acute electrical baroreflex stimulation.
abstract: We intended to determine if acute baroreflex activation therapy (BAT) increases venous capacitance and aortic conductance. BAT is effective in resistant hypertension, but its effect on the systemic vasculature is poorly understood. Left ventricular (LV) and aortic pressures and subdiaphragmatic aortic and caval flows (ultrasonic) were measured in six anesthetized dogs. Changes in abdominal blood volume (Vabdominal) were estimated as the integrated difference in abdominal aortic inflow and caval outflow. An electrode was implanted on the right carotid sinus. Data were measured during control and BAT. Next, sodium nitroprusside (SNP) was infused and BAT was subsequently added. Finally, angiotensin II (ANG II) was infused, and three increased BAT currents were added. We found that BAT decreased mean aortic pressure (PAo) by 22.5 ± 1.3 mmHg (P < 0.001) and increased aortic conductance by 16.2 ± 4.9% (P < 0.01) and Vabdominal at a rate of 2.2 ± 0.6 ml·kg(-1)·min(-1) (P < 0.01). SNP decreased PAo by 17.4 ± 0.7 mmHg (P < 0.001) and increased Vabdominal at a rate of 2.2 ± 0.7 ml·kg(-1)·min(-1) (P < 0.05). During the SNP infusion, BAT decreased PAo further, by 26.0 ± 2.1 mmHg (P < 0.001). ANG II increased PAo by 40.4 ± 3.5 mmHg (P = 0.001). When an increased BAT current was added, PAo decreased to baseline (P < 0.01) while aortic conductance increased from 62.3 ± 5.2% to 80.2 ± 3.3% (P < 0.05) of control. Vabdominal increased at a rate of 1.8 ± 0.9 ml·kg(-1)·min(-1) (P < 0.01), reversing the ANG II effects. In conclusion, BAT increases arterial conductance, decreases PAo, and increases venous capacitance even in the presence of powerful vasoactive drugs. Increasing venous capacitance may be an important effect of BAT in hypertension.
authors.affiliation: Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada;
authors.forename: Steven
authors.initials: S
authors.lastname: Burgoyne
authors.affiliation: CVRx, Inc., Minneapolis, Minnesota.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Georgakopoulos
authors.affiliation: Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada; Department of Medicine, University of Calgary, Calgary, Alberta, Canada; Department of Cardiac Sciences, University of Calgary, Calgary, Alberta, Canada;
authors.forename: Israel
authors.initials: I
authors.lastname: Belenkie
authors.affiliation: Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada; Department of Cardiac Sciences, University of Calgary, Calgary, Alberta, Canada; Department of Physiology/Pharmacology, University of Calgary, Calgary, Alberta, Canada; and jtyberg@ucalgary.ca.
authors.forename: John V
authors.initials: JV
authors.lastname: Tyberg
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000502:physiology; D062186:Arterial Pressure; D017704:Baroreflex / Q000187:drug effects; D001783:Blood Flow Velocity; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D023421:Models, Animal; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D012039:Regional Blood Flow; D013997:Time Factors; D018924:Vascular Capacitance; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology; D014682:Vena Cava, Inferior / Q000502:physiology; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents
keywords: aortic conductance; baroreceptors; venous capacitance