title: Prognostic value of indeterminable anaerobic threshold in heart failure.
abstract: BACKGROUND
  In patients with heart failure (HF), during maximal cardiopulmonary exercise test, anaerobic threshold (AT) is not always identified. We evaluated whether this finding has a prognostic meaning.
  
  
  RESULTS
  We recruited and prospectively followed up, in 14 dedicated HF units, 3058 patients with systolic (left ventricular ejection fraction <40%) HF in stable clinical conditions, New York Heart Association class I to III, who underwent clinical, laboratory, echocardiographic, and cardiopulmonary exercise test investigations at study enrollment. We excluded 921 patients who did not perform a maximal exercise, based on lack of achievement of anaerobic metabolism (peak respiratory quotient ≤1.05). Primary study end point was a composite of cardiovascular death and urgent cardiac transplant, and secondary end point was all-cause death. Median follow-up was 3.01 (1.39-4.98) years. AT was identified in 1935 out of 2137 patients (90.54%). At multivariable logistic analysis, failure in detecting AT resulted significantly in reduced peak oxygen uptake and higher metabolic exercise and cardiac and kidney index score value, a powerful prognostic composite HF index (P<0.001). At multivariable analysis, the following variables were significantly associated with primary study end point: peak oxygen uptake (% pred; P<0.001; hazard ratio [HR]=0.977; confidence interval [CI]=0.97-0.98), ventilatory efficiency slope (P=0.01; HR=1.02; CI=1.01-1.03), hemoglobin (P<0.05; HR=0.931; CI=0.87-1.00), left ventricular ejection fraction (P<0.001; HR=0.948; CI=0.94-0.96), renal function (modification of diet in renal disease; P<0.001; HR=0.990; CI=0.98-0.99), sodium (P<0.05; HR=0.967; CI=0.94-0.99), and AT nonidentification (P<0.05; HR=1.41; CI=1.06-1.89). Nonidentification of AT remained associated to prognosis also when compared with metabolic exercise and cardiac and kidney index score (P<0.01; HR=1.459; CI=1.09-1.10). Similar results were obtained for the secondary study end point.
  
  
  CONCLUSIONS
  The inability to identify AT most often occurs in patients with severe HF, and it has an independent prognostic role in HF.
authors.affiliation: Centro Cardiologico Monzino, IRCCS, Milano, Italy.
authors.forename: Piergiuseppe
authors.initials: P
authors.lastname: Agostoni
authors.forename: Ugo
authors.initials: U
authors.lastname: Corrà
authors.forename: Gaia
authors.initials: G
authors.lastname: Cattadori
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Veglia
authors.forename: Elisa
authors.initials: E
authors.lastname: Battaia
authors.forename: Rocco
authors.initials: R
authors.lastname: La Gioia
authors.forename: Angela B
authors.initials: AB
authors.lastname: Scardovi
authors.forename: Michele
authors.initials: M
authors.lastname: Emdin
authors.forename: Marco
authors.initials: M
authors.lastname: Metra
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Sinagra
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Limongelli
authors.forename: Rosa
authors.initials: R
authors.lastname: Raimondo
authors.forename: Federica
authors.initials: F
authors.lastname: Re
authors.forename: Marco
authors.initials: M
authors.lastname: Guazzi
authors.forename: Romualdo
authors.initials: R
authors.lastname: Belardinelli
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Parati
authors.forename: Damiano
authors.initials: D
authors.lastname: Magrì
authors.forename: Cesare
authors.initials: C
authors.lastname: Fiorentini
authors.forename: Mariantonietta
authors.initials: M
authors.lastname: Cicoira
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Salvioni
authors.forename: Marta
authors.initials: M
authors.lastname: Giovannardi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Mezzani
authors.forename: Domenico
authors.initials: D
authors.lastname: Scrutinio
authors.forename: Andrea
authors.initials: A
authors.lastname: Di Lenarda
authors.forename: Valentina
authors.initials: V
authors.lastname: Mantegazza
authors.forename: Roberto
authors.initials: R
authors.lastname: Ricci
authors.forename: Anna
authors.initials: A
authors.lastname: Apostolo
authors.forename: Annamaria
authors.initials: A
authors.lastname: Iorio
authors.forename: Stefania
authors.initials: S
authors.lastname: Paolillo
authors.forename: Pietro
authors.initials: P
authors.lastname: Palermo
authors.forename: Mauro
authors.initials: M
authors.lastname: Contini
authors.forename: Corrado
authors.initials: C
authors.lastname: Vassanelli
authors.forename: Claudio
authors.initials: C
authors.lastname: Passino
authors.forename: Massimo F
authors.initials: MF
authors.lastname: Piepoli
mesh_terms: D000368:Aged; D015308:Anaerobic Threshold; D016009:Chi-Square Distribution; D004734:Energy Metabolism; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000378:metabolism / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D016027:Heart Transplantation; D006801:Humans; D007558:Italy; D053208:Kaplan-Meier Estimate; D007668:Kidney / Q000503:physiopathology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013318:Stroke Volume; D013997:Time Factors; D016277:Ventricular Function, Left
keywords: exercise; follow-up studies; heart failure; oxygen; prognosis