title: The VO(2)-on kinetics in constant load exercise sub-anaerobic threshold reflects endothelial function and dysfunction in muscle microcirculation.
abstract: To propose a test to evaluate endothelial function, based on VO(2) on-transition kinetics in sub-anaerobic threshold (AT) constant load exercise, we tested healthy subjects and patients with ischemic-hypertensive cardiopathy by two cardiopulmonary tests on a cycle ergometer endowed with an electric motor to overcome initial inertia: a pre-test and, after at least 24 h, one 6 min constant load exercise at 90 % AT. We measured net phase 3 VO(2)-on kinetics and, by phase 2 time constant (tau), valued endothelial dysfunction. We found shorter tau in repeated tests, shorter time between first and second test, by persisting endothelium-dependent arteriolar vasodilatation and/or several other mechanisms. Reducing load to 80 % and 90 % AT did not produce significant changes in tau of healthy volunteers, while in heart patients an AT load of 70 %, compared to 80 % AT, shortened tau (delta=4.38+/-1.65 s, p=0.013). In heart patients, no correlation was found between NYHA class, ejection fraction (EF), and the two variables derived from incremental cycle cardio-pulmonary exercise, as well as between EF and tau; while NYHA class groups were well correlated with tau duration (r=0.92, p=0.0001). Doxazosin and tadalafil also significantly reduced tau. In conclusion, the O(2) consumption kinetics during the on-transition of constant load exercise below the anaerobic threshold are highly sensitive to endothelial function in muscular microcirculation, and constitute a marker for the evaluation of endothelial dysfunction.
authors.affiliation: Department of Medicine and Surgery Sciences, University of Bologna, Italy. claudio.borghi@unibo.it.
authors.forename: D
authors.initials: D
authors.lastname: Maione
authors.forename: A Fg
authors.initials: AF
authors.lastname: Cicero
authors.forename: S
authors.initials: S
authors.lastname: Bacchelli
authors.forename: E R
authors.initials: ER
authors.lastname: Cosentino
authors.forename: D
authors.initials: D
authors.lastname: Degli Esposti
authors.forename: D N
authors.initials: DN
authors.lastname: Manners
authors.forename: E R
authors.initials: ER
authors.lastname: Rinaldi
authors.forename: M
authors.initials: M
authors.lastname: Rosticci
authors.forename: R
authors.initials: R
authors.lastname: Senaldi
authors.forename: E
authors.initials: E
authors.lastname: Ambrosioni
authors.forename: C
authors.initials: C
authors.lastname: Borghi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015308:Anaerobic Threshold; D016022:Case-Control Studies; D004730:Endothelium, Vascular / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D009132:Muscles / Q000098:blood supply; D017202:Myocardial Ischemia / Q000503:physiopathology*