title: Blood pressure reduction after gastric bypass surgery is explained by a decrease in cardiac output.
abstract: Blood pressure (BP) decreases in the first weeks after Roux-and-Y gastric bypass surgery. Yet the pathophysiology of the BP-lowering effects observed after gastric bypass surgery is incompletely understood. We evaluated BP, systemic hemodynamics, and baroreflex sensitivity in 15 obese women[mean age 42 ± 7 standard deviation (SD) yr, body mass index 45 ± 6 kg/m2] 2 wk before and 6 wk following Roux-and-Y gastric bypass surgery. Six weeks after gastric bypass surgery, mean body weight decreased by 13 ± 5 kg (10%, P < 0.001). Office BP decreased from 137 ± 10/86 ± 6 to 128 ± 12/81 ± 9 mmHg (P < 0.001, P < 0.01), while daytime ambulatory BP decreased from 128 ± 14/80 ± 9 to 114 ± 10/73 ± 6 mmHg (P = 0.01, P = 0.05), whereas nighttime BP decreased from 111 ± 13/66 ± 7 to 102 ± 9/62 ± 7 mmHg (P = 0.04, P < 0.01). The decrease in BP was associated with a 1.6 ± 1.2 l/min (20%, P < 0.01) decrease in cardiac output (CO), while systemic vascular resistance increased (153 ± 189 dyn·s·cm-5, 15%, P < 0.01). The maximal ascending slope in systolic blood pressure decreased (192 mmHg/s, 19%, P = 0.01), suggesting a reduction in left ventricular contractility. Baroreflex sensitivity increased from 9.0 [6.4-14.3] to 13.8 [8.5-19.0] ms/mmHg (median [interquartile range]; P < 0.01) and was inversely correlated with the reductions in heart rate (R = -0.64, P = 0.02) and CO (R = -0.61, P = 0.03). In contrast, changes in body weight were not correlated with changes in either BP or CO. The BP reduction following Roux-and-Y gastric bypass surgery is correlated with a decrease in CO independent of changes in body weight. The contribution of heart rate to the reduction in CO together with enhanced baroreflex sensitivity suggests a shift toward increased parasympathetic cardiovascular control.
  The reason for the decrease in blood pressure (BP) in the first weeks after gastric bypass surgery remains to be elucidated. We show that the reduction in BP following surgery is caused by a decrease in cardiac output. In addition, the maximal ascending slope in systolic blood pressure decreased suggesting a reduction in left ventricular contractility and cardiac workload. These findings help to understand the physiological changes following gastric bypass surgery and are relevant in light of the increased risk of heart failure in these patients.
authors.affiliation: Department of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Peter M
authors.initials: PM
authors.lastname: van Brussel
authors.affiliation: Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Bas
authors.initials: B
authors.lastname: van den Bogaard
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Barbara A
authors.initials: BA
authors.lastname: de Weijer
authors.affiliation: Laboratory for Clinical Cardiovascular Physiology, Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jasper
authors.initials: J
authors.lastname: Truijen
authors.affiliation: Department of Nephrology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: C T Paul
authors.initials: CT
authors.lastname: Krediet
authors.affiliation: Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands.
authors.forename: Ignace M
authors.initials: IM
authors.lastname: Janssen
authors.affiliation: Department of Surgery, Slotervaart Hospital, Amsterdam, The Netherlands.
authors.forename: Arnold
authors.initials: A
authors.lastname: van de Laar
authors.affiliation: Department of Internal Medicine, University Medical Center, Utrecht, The Netherlands; and.
authors.forename: Karin
authors.initials: K
authors.lastname: Kaasjager
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Eric
authors.initials: E
authors.lastname: Fliers
authors.affiliation: Laboratory for Clinical Cardiovascular Physiology, Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.|School of Biomedical Sciences, University of Nottingham Medical School, Queen's Medical Center, Nottingham, United Kingdom.
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: van Lieshout
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Mireille J
authors.initials: MJ
authors.lastname: Serlie
authors.affiliation: Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; b.j.vandenborn@amc.nl.
authors.forename: Bert-Jan H
authors.initials: BH
authors.lastname: van den Born
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D015992:Body Mass Index; D002302:Cardiac Output / Q000502:physiology*; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects*; D006321:Heart / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006352:Heart Ventricles / Q000503:physiopathology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D009765:Obesity / Q000503:physiopathology / Q000601:surgery; D010275:Parasympathetic Nervous System / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology
keywords: bariatric surgery; baroreflex sensitivity; blood pressure; hemodynamics; obesity