title: Body position and activity, but not heart rate, affect pump flows in patients with continuous-flow left ventricular assist devices.
abstract: OBJECTIVE
  The aim of this study was to determine the contribution of pre-load and heart rate to pump flow in patients implanted with continuous-flow left ventricular assist devices (cfLVADs).
  
  
  BACKGROUND
  Although it is known that cfLVAD pump flow increases with exercise, it is unclear if this increment is driven by increased heart rate, augmented intrinsic ventricular contraction, or enhanced venous return.
  
  
  METHODS
  Two studies were performed in patients implanted with the HeartWare HVAD. In 11 patients, paced heart rate was increased to approximately 40 beats/min above baseline and then down to approximately 30 beats/min below baseline pacing rate (in pacemaker-dependent patients). Ten patients underwent tilt-table testing at 30°, 60°, and 80° passive head-up tilt for 3 min and then for a further 3 min after ankle flexion exercise. This regimen was repeated at 20° passive head-down tilt. Pump parameters, noninvasive hemodynamics, and 2-dimensional echocardiographic measures were recorded.
  
  
  RESULTS
  Heart rate alteration by pacing did not affect LVAD flows or LV dimensions. LVAD pump flow decreased from baseline 4.9 ± 0.6 l/min to approximately 4.5 ± 0.5 l/min at each level of head-up tilt (p < 0.0001 analysis of variance). With active ankle flexion, LVAD flow returned to baseline. There was no significant change in flow with a 20° head-down tilt with or without ankle flexion exercise. There were no suction events.
  
  
  CONCLUSIONS
  Centrifugal cfLVAD flows are not significantly affected by changes in heart rate, but they change significantly with body position and passive filling. Previously demonstrated exercise-induced changes in pump flows may be related to altered loading conditions, rather than changes in heart rate.
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Muthiah
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Sunil
authors.initials: S
authors.lastname: Gupta
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Otton
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Desiree
authors.initials: D
authors.lastname: Robson
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Robyn
authors.initials: R
authors.lastname: Walker
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Andre
authors.initials: A
authors.lastname: Tay
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Macdonald
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Anne
authors.initials: A
authors.lastname: Keogh
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Eugene
authors.initials: E
authors.lastname: Kotlyar
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Emily
authors.initials: E
authors.lastname: Granger
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Kumud
authors.initials: K
authors.lastname: Dhital
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Phillip
authors.initials: P
authors.lastname: Spratt
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Jansz
authors.affiliation: Heart Failure and Transplant Unit, St. Vincent's Hospital and Victor Chang Cardiac Research Institute, Sydney, Australia. Electronic address: cshayward@stvincents.com.au.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Hayward
mesh_terms: D001021:Aortic Valve / Q000502:physiology; D062186:Arterial Pressure / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D002304:Cardiac Pacing, Artificial / Q000379:methods; D009202:Cardiomyopathies / Q000503:physiopathology / Q000628:therapy; D015444:Exercise / Q000502:physiology*; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006353:Heart-Assist Devices; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D018667:Tilt-Table Test; D018497:Ventricular Dysfunction, Right / Q000503:physiopathology / Q000628:therapy
keywords: LVAD; exercise; heart rate; posture; tilt-table