title: Effect of acute β-blocker withholding on ventilatory efficiency in patients with advanced chronic heart failure.
abstract: BACKGROUND
  This is the first study to examine the effect of acute (24-hour) beta-blocker withholding on ventilatory efficiency in patients with advanced chronic heart failure (CHF) during maximal incremental treadmill cardiopulmonary exercise test.
  
  
  RESULTS
  Seventeen CHF patients were studied either 3 hours after administration of beta-blocker (BB(ON)) or 27 hours after the last beta-blocker ingestion (BB(OFF)). The ventilatory efficiency was measured via the slope of the linear relationship between ventilation (V'(E)) and carbon dioxide production (V'CO2) (ie, V'(E)/V'CO2 slope). Measurements were also made at rest, anaerobic threshold (AT), maximal end-tidal pressure for carbon dioxide (P(ET)CO2max), respiratory compensation point (RC), and peak exercise. Compared with BB(ON), the V'(E)/V'CO2 slope was significantly increased during BB(OFF) (30.8 +/- 7.4 vs. 29.1 +/- 5.4, P = .04). At peak exercise, oxygen uptake (V'O2, 16.0 +/- 2.7 vs. 15.6 +/- 2.8 mL x kg x min) and V'CO2 (1458 +/- 459 vs. 1414 +/- 429 mL/min) were not different between the 2 conditions, whereas V'(E) was higher during BB(OFF) (49.5 +/- 10.7 vs. 46.1 +/- 9.6 L/min, P = .04). No differences were noted at AT and RC in V'O2, V'CO2, V'(E), V'(E)/V'O2, and V'(E)/V'CO2 ratios during the 2 conditions. At P(ET)CO2max, used to noninvasively estimate the CO2 set point, V'(E) was higher (33.9 +/- 7.6 vs. 31.7 +/- 7.3 L/min, P = .002) and P(ET)CO2 was lower (37.4 +/- 4.8 vs. 38.5 +/- 4.0 mm Hg, P = .03), whereas V'CO2 was unchanged (1079 +/- 340 vs. 1050 +/- 322 mL/min) during BB(OFF).
  
  
  CONCLUSIONS
  Acute beta-blocker withholding resulted in decreased ventilatory efficiency mostly from an increase of V'CO2-independent regulation of V'(E) and less likely from a change in ventilation/perfusion mismatching.
authors.affiliation: Department of Medicine, Division of Cardiology, Columbia University Medical Center, New York, NY 10032, USA.
authors.forename: Pierantonio
authors.initials: P
authors.lastname: Laveneziana
authors.forename: Piergiuseppe
authors.initials: P
authors.lastname: Agostoni
authors.forename: Andrea
authors.initials: A
authors.lastname: Mignatti
authors.forename: Saima
authors.initials: S
authors.lastname: Mushtaq
authors.forename: Paolo
authors.initials: P
authors.lastname: Colombo
authors.forename: Daniel
authors.initials: D
authors.lastname: Sims
authors.forename: Nir
authors.initials: N
authors.lastname: Uriel
authors.forename: Ulrich P
authors.initials: UP
authors.lastname: Jorde
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000328:Adult; D002908:Chronic Disease; D018592:Cross-Over Studies; D005080:Exercise Test / Q000187:drug effects / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000188:drug therapy* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange / Q000187:drug effects / Q000502:physiology; D012123:Pulmonary Ventilation / Q000187:drug effects* / Q000502:physiology*; D013997:Time Factors
chemical_list: D000319:Adrenergic beta-Antagonists