Differential Responses of Post-Exercise Recovery of Leg Blood Flow and Oxygen Uptake Kinetics in HFpEF versus HFrEF

• Published in: PloS one Vol. 11; no. 10; p. e0163513
• Main Authors: Thompson, Richard B, Pagano, Joseph J, Mathewson, Kory W, Paterson, Ian, Dyck, Jason R, Kitzman, Dalane W, Haykowsky, Mark J
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04.10.2016; Public Library of Science (PLoS)
• Subjects: Aged; Biology and Life Sciences; Biomedical engineering; Blood; Blood flow; Blood Pressure; Brain research; Cardiac patients; Cardiology; Exercise; Exercise intensity; Exercise Therapy; Exercise Tolerance; Female; Femur; Flow; Health aspects; Heart; Heart diseases; Heart failure; Heart Failure - physiopathology; Heart Rate; Hemodynamics; Humans; Kinetics; Knee; Leg; Leg - blood supply; Magnetic fields; Magnetic Resonance Angiography; Magnetic resonance imaging; Male; Medical research; Medicine and Health Sciences; Middle Aged; Mortality; Muscle, Skeletal - blood supply; Muscle, Skeletal - metabolism; Muscles; Musculoskeletal system; NMR; Nuclear magnetic resonance; Oxygen; Oxygen Consumption; Oxygen uptake; Patients; Physical fitness; Physical Sciences; Recovery; Recovery (Medical); Research and Analysis Methods; Saturation; Spectrum analysis; Stroke Volume; Veins & arteries
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0163513

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.