P3.21 Conductance and Capacitance Effects of Acute, Electrical, Carotid Baroreflex Stimulation

Abstract

Baroreflex activation therapy (BAT) is effective in resistant hypertension; we hypothesized that BAT increases both venous capacitance and arterial conductance. We measured aortic pressure and flow and inferior vena caval flow and used a modified Brooksby-Donald technique to evaluate sub-diaphragmatic blood volume. Data were recorded with BAT, and with sodium nitroprusside (SNP) and Angiotensin II (Ang II) infusions, alone and with BAT.BAT substantially increased venous capacitance and arterial conductance. SNP also increased venous capacitance and arterial conductance. During SNP infusion BAT remained effective, further decreasing blood pressure and increasing capacitance and conductance. Ang II decreased both capacitance and conductance. During Ang II infusion, increased BAT reversed the decrease in venous capacitance while restoring BP completely and conductance to 80% of baseline.BAT decreases blood pressure and increases arterial conductance and venous capacitance, even when combined with powerful vasoactive drugs. These may be important effects in hypertension.iii Acknowledgements I would like to thank those who contributed directly to this thesis and my graduate studies experience, including Nigel Shrive, Israel Belenkie, and Jim Georgakopoulos. Nigel and Israel's experience and approachability, and Jim's knowledge and enthusiasm for research make them excellent collaborators. The relationship between the Tyberg lab and CVRx has provided insight into the challenges of medical device development, as well as access to unique research tools. The results in this thesis represent only a fraction of my experience gained as a graduate student in Biomedical Engineering. The lab's relationship with the Stephenson Cardiovascular MRI Centre, facilitated by Jacqueline McQuaker, represents one of many opportunities I've had to explore research beyond my own work. Working in the lab would not have been so successful and enjoyable without the company of my colleagues. Post-Doctoral fellows Jamie Mitchell and Chris Bouwmeester were good company and always generous with their knowledge. It has been a pleasure to share the chores and challenges of graduate work with fellow students Kristen Handkammer and LindsayBurrowes. Technical support from John Nystrom has always kept our excuses to a minimum.Not enough can be said in thanking my family. As with most of my endeavours, their support has facilitated my studies. While their support is never failing, I shall never take it for granted.Finally, I would like to thank the two constants of the Tyberg lab; Cheryl Meek and John Tyberg.Cheryl's technical expertise and surgical success have translated into greater and greater demands from us, which she typically meets with more success. Her collegial nature is likely the reason why nobody has the need to develop their conflict resolutions skills while working in her lab.To talk about John Tyberg as a supervisor, researcher, mentor, and friend, without repeating the accolades that every student before has spoken of him would be impos...