title: Differential Responses of Post-Exercise Recovery of Leg Blood Flow and Oxygen Uptake Kinetics in HFpEF versus HFrEF.
abstract: The goals of the current study were to compare leg blood flow, oxygen extraction and oxygen uptake (VO2) after constant load sub-maximal unilateral knee extension (ULKE) exercise in patients with heart failure with reduced ejection fraction (HFrEF) compared to those with preserved ejection fraction (HFpEF). Previously, it has been shown that prolonged whole body VO2 recovery kinetics are directly related to disease severity and all-cause mortality in HFrEF patients. To date, no study has simultaneously measured muscle-specific blood flow and oxygen extraction post exercise recovery kinetics in HFrEF or HFpEF patients; therefore it is unknown if muscle VO2 recovery kinetics, and more specifically, the recovery kinetics of blood flow and oxygen extraction at the level of the muscle, differ between HF phenotypes. Ten older (68±10yrs) HFrEF (n = 5) and HFpEF (n = 5) patients performed sub-maximal (85% of maximal weight lifted during an incremental test) ULKE exercise for 4 minutes. Femoral venous blood flow and venous O2 saturation were measured continuously from the onset of end-exercise, using a novel MRI method, to determine off-kinetics (mean response times, MRT) for leg VO2 and its determinants. HFpEF and HFrEF patients had similar end-exercise leg blood flow (1.1±0.6 vs. 1.2±0.6 L/min, p>0.05), venous saturation (42±12 vs. 41±11%, p>0.05) and VO2 (0.13±0.08 vs. 0.11±0.05 L/min, p>0.05); however HFrEF had significantly delayed recovery MRT for flow (292±135sec. vs 105±63sec., p = 0.004) and VO2 (95±37sec. vs. 47±15sec., p = 0.005) compared to HFpEF. Impaired muscle VO2 recovery kinetics following ULKE exercise differentiated HFrEF from HFpEF patients and suggests distinct underlying pathology and potential therapeutic approaches in these populations.
authors.affiliation: Department of Biomedical Engineering, University of Alberta, Edmonton, Canada.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Thompson
authors.affiliation: Department of Biomedical Engineering, University of Alberta, Edmonton, Canada.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Pagano
authors.affiliation: Department of Biomedical Engineering, University of Alberta, Edmonton, Canada.
authors.forename: Kory W
authors.initials: KW
authors.lastname: Mathewson
authors.affiliation: Division of Cardiology, Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Paterson
authors.affiliation: Department of Pediatrics and Pharmacology, University of Alberta, Edmonton, Canada.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Dyck
authors.affiliation: Cardiology and Geriatrics, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States of America.
authors.forename: Dalane W
authors.initials: DW
authors.lastname: Kitzman
authors.affiliation: College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas, United States of America.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Haykowsky
mesh_terms: D000368:Aged; D001794:Blood Pressure; D015444:Exercise; D005081:Exercise Therapy; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007700:Kinetics; D007866:Leg / Q000098:blood supply*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*; D010101:Oxygen Consumption; D013318:Stroke Volume