title: Enhanced ventilatory response to exercise in patients with chronic heart failure and central sleep apnea.
abstract: BACKGROUND
  In patients with chronic heart failure (CHF), central sleep apnea (CSA) and enhanced ventilatory response (VE/VCO2 slope) to exercise are common. Both breathing disorders alone indicate poor prognosis in CHF. Although augmented chemosensitivity to CO2 is thought to be one important underlying mechanism for both breathing disorders, it is unclear whether both breathing disorders are related closely in patients with CHF.
  
  
  RESULTS
  We investigated 20 CHF patients with clinically important CSA (apnea-hypopnea-index (AHI), number of episodes per hour >or=15) and 10 CHF patients without CSA. Patients with and without CSA did not differ with respect to exercise capacity (peak VO2, 63.4+/-3.4% versus 60.8+/-4.4% of predicted value; P=0.746) and left ventricular ejection fraction (LVEF, 31+/-2% versus 31+/-3%; P=0.948). The AHI was not correlated with exercise capacity (peak VO2, percent of predicted value; P=0.260) and LVEF (percent, P=0.886). In contrast, the positive correlation of the VE/VCO2 slope, determined by cardiopulmonary exercise testing, with the AHI was highly significant (P<0.001). The VE/VCO2 slope was significantly increased in patients with CSA compared with those without CSA (29.7 versus 24.9; P<0.001).
  
  
  CONCLUSIONS
  The ventilatory response to exercise is significantly augmented in CHF patients with CSA compared with those without. In contrast to peak VO2 and LVEF, the VE/VCO2 slope is strongly related to the severity of CSA in patients with CHF, which underscores an augmented chemosensitivity to CO2 as a common underlying pathophysiological mechanism.
authors.affiliation: Klinik und Poliklinik für Innere Medizin II, Universität Regensburg, Germany. michael.arzt@klinik.uni-regensburg.de
authors.forename: Michael
authors.initials: M
authors.lastname: Arzt
authors.forename: Martina
authors.initials: M
authors.lastname: Harth
authors.forename: Andreas
authors.initials: A
authors.lastname: Luchner
authors.forename: Frank
authors.initials: F
authors.lastname: Muders
authors.forename: Stephan R
authors.initials: SR
authors.lastname: Holmer
authors.forename: Friedrich C
authors.initials: FC
authors.lastname: Blumberg
authors.forename: Günter A J
authors.initials: GA
authors.lastname: Riegger
authors.forename: Michael
authors.initials: M
authors.lastname: Pfeifer
mesh_terms: D002908:Chronic Disease; D005080:Exercise Test; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D016014:Linear Models; D010101:Oxygen Consumption; D005082:Physical Exertion; D011237:Predictive Value of Tests; D012123:Pulmonary Ventilation; D012372:ROC Curve; D020182:Sleep Apnea, Central / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D012894:Sleep Stages; D013318:Stroke Volume