title: Changes in subendocardial viability ratio with acute high-altitude exposure and protective role of acetazolamide.
abstract: High-altitude tourism is increasingly frequent, involving also subjects with manifest or subclinical coronary artery disease. Little is known, however, on the effects of altitude exposure on factors affecting coronary perfusion. The aim of our study was to assess myocardial oxygen supply/demand ratio in healthy subjects during acute exposure at high altitude and to evaluate the effect of acetazolamide on this parameter. Forty-four subjects (21 men, age range: 24-59 years) were randomized to double-blind acetazolamide 250 mg bid or placebo. Subendocardial viability ratio and oxygen supply/demand ratio were estimated on carotid artery by means of a validated PulsePen tonometer, at sea level, before and after treatment, and after acute and more prolonged exposure to high altitude (4559 m). On arrival at high altitude, subendocardial viability ratio was reduced in both placebo (from 1.63±0.15 to 1.18±0.17; P<0.001) and acetazolamide (from 1.68±0.25 to 1.35±0.18; P<0.001) groups. Subendocardial viability ratio returned to sea level values (1.65±0.24) after 3 days at high altitude under acetazolamide but remained lower than at sea level under placebo (1.42±0.22; P<0.005 versus baseline). At high altitude, oxygen supply/demand ratio fell both under placebo (from 29.6±4.0 to 17.3±3.0; P<0.001) and acetazolamide (from 32.1±7.0 to 22.3±4.6; P<0.001), its values remaining always higher (P<0.001) on acetazolamide. Administration of acetazolamide may, thus, antagonize the reduction in subendocardial oxygen supply triggered by exposure to hypobaric hypoxia. Further studies involving also subjects with known or subclinical coronary artery disease are needed to confirm a protective action of acetazolamide on myocardial viability under high-altitude exposure.
authors: Department of Cardiology, San Luca Hospital, IRCCS Istituto Auxologico Italiano, Milan, Italy.
authors: Paolo
authors: P
authors: Salvi
authors: Miriam
authors: M
authors: Revera
authors: Andrea
authors: A
authors: Faini
authors: Andrea
authors: A
authors: Giuliano
authors: Francesca
authors: F
authors: Gregorini
authors: Piergiuseppe
authors: P
authors: Agostoni
authors: Carlos G Ramos
authors: CG
authors: Becerra
authors: Grzegorz
authors: G
authors: Bilo
authors: Carolina
authors: C
authors: Lombardi
authors: Michael F
authors: MF
authors: O'Rourke
authors: Giuseppe
authors: G
authors: Mancia
authors: Gianfranco
authors: G
authors: Parati
mesh_terms: D000086:Acetazolamide / Q000008:administration & dosage*; D000208:Acute Disease; D000328:Adult; D000532:Altitude Sickness / Q000097:blood / Q000503:physiopathology / Q000517:prevention & control*; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage; D003326:Coronary Circulation / Q000187:drug effects* / Q000502:physiology; D003331:Coronary Vessels / Q000187:drug effects / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D000086:Acetazolamide