title: Caffeine prolongs exercise duration in heart failure.
abstract: BACKGROUND
  Caffeine increases submaximal exercise performance in healthy young subjects; its effects on exercise tolerance in heart failure (HF) have not been characterized.
  
  
  RESULTS
  To determine whether caffeine increases exercise tolerance in HF, caffeine (4 mg/kg intravenously, equivalent to 2 cups of coffee) or vehicle were infused into 10 treated HF patients (left ventricular ejection fraction 25 +/- 2 %), and 10 age-matched normal subjects (N) on 2 separate days in a double-blind, randomized, crossover design. We measured heart rate, blood pressure, and ventilation at rest and during graded cycling (15 W/minute) to peak effort. Peak oxygen consumption was unaffected in either group. Mean exercise time was unchanged in N (1,013 +/- 87 versus 988 +/- 107 seconds; P = .86) but was significantly increased by caffeine in HF (from 511 +/- 28 to 560 +/- 37 seconds; P = .004) despite an increase in peak minute ventilation (P < .05). Resting and peak blood pressures were higher after caffeine (P < .05) in HF, not N.
  
  
  CONCLUSIONS
  Caffeine allows HF patients to exercise longer at peak effort.
authors.affiliation: Division of Cardiology and Faculty of Medicine, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Catherine F
authors.initials: CF
authors.lastname: Notarius
authors.forename: Beverley
authors.initials: B
authors.lastname: Morris
authors.forename: John S
authors.initials: JS
authors.lastname: Floras
mesh_terms: D000328:Adult; D000368:Aged; D002110:Caffeine / Q000494:pharmacology*; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D013997:Time Factors
chemical_list: D002110:Caffeine