title: Understanding exercise-induced hyperemia: central and peripheral hemodynamic responses to passive limb movement in heart transplant recipients.
abstract: To better characterize the contribution of both central and peripheral mechanisms to passive limb movement-induced hyperemia, we studied nine recent (<2 yr) heart transplant (HTx) recipients (56 ± 4 yr) and nine healthy controls (58 ± 5 yr). Measurements of heart rate (HR), stroke volume (SV), cardiac output (CO), and femoral artery blood flow were recorded during passive knee extension. Peripheral vascular function was assessed using brachial artery flow-mediated dilation (FMD). During passive limb movement, the HTx recipients lacked an HR response (0 ± 0 beats/min, Δ0%) but displayed a significant increase in CO (0.4 ± 0.1 l/min, Δ5%) although attenuated compared with controls (1.0 ± 0.2 l/min, Δ18%). Therefore, the rise in CO in the HTx recipients was solely dependent on increased SV (5 ± 1 ml, Δ5%) in contrast with the controls who displayed significant increases in both HR (6 ± 2 beats/min, Δ11%) and SV (5 ± 2 ml, Δ7%). The transient increase in femoral blood volume entering the leg during the first 40 s of passive movement was attenuated in the HTx recipients (24 ± 8 ml) compared with controls (93 ± 7 ml), whereas peripheral vascular function (FMD) appeared similar between HTx recipients (8 ± 2%) and controls (6 ± 1%). These data reveal that the absence of an HR increase in HTx recipients significantly impacts the peripheral vascular response to passive movement in this population and supports the concept that an increase in CO is a major contributor to exercise-induced hyperemia.
authors.affiliation: Geriatric Research Education and Clinical Center, Department of Internal Medicine, George E.Whalen Veterans Affairs Medical Center, Salt Lake City, Utah, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Hayman
authors.forename: Jose N
authors.initials: JN
authors.lastname: Nativi
authors.forename: Josef
authors.initials: J
authors.lastname: Stehlik
authors.forename: John
authors.initials: J
authors.lastname: McDaniel
authors.forename: Anette S
authors.initials: AS
authors.lastname: Fjeldstad
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ives
authors.forename: D
authors.initials: D
authors.lastname: Walter Wray
authors.forename: Feras
authors.initials: F
authors.lastname: Bader
authors.forename: Edward M
authors.initials: EM
authors.lastname: Gilbert
authors.forename: Russell S
authors.initials: RS
authors.lastname: Richardson
mesh_terms: D001810:Blood Volume / Q000502:physiology; D002248:Carbon Monoxide / Q000378:metabolism; D002302:Cardiac Output / Q000502:physiology; D016022:Case-Control Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D005263:Femoral Artery / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D016027:Heart Transplantation / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology*; D007866:Leg / Q000098:blood supply* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology
chemical_list: D002248:Carbon Monoxide