title: Alleviation of pulmonary hypertension by cardiac resynchronization therapy is associated with improvement in central sleep apnea.
abstract: BACKGROUND
  Recent studies have demonstrated that cardiac resynchronization therapy (CRT) reduces sleep apnea in heart failure (HF); however, the mechanism of benefit remains unclear.
  
  
  METHODS
  Overnight polysomnography (PSG) was performed in consecutive HF patients who were scheduled for CRT implant. Patients with sleep apnea defined by an apnea-hypopnea index (AHI) of >10/hour were recruited and underwent echocardiogram examination at baseline and 3 months after CRT.
  
  
  RESULTS
  Among 37 HF patients screened, 20 patients (54%) had sleep apnea and 15 of them consented for the study. After 3 months of CRT, there was a significant improvement in New York Heart Association functional class (3.1+/-0.1 vs 2.1+/-0.1, P<0.01), quality-of-life (QoL) score (62.9+/-3.3 vs 56.1+/-4.5, P=0.02), left ventricular ejection fraction (LVEF, 28.8+/-2.5% vs 38.1+/-2.3%, P<0.01), and reduction in pulmonary artery systolic pressure (PASP, 41.0+/-2.7 vs 28.6+/-2.2 mmHg; P<0.01) compared with baseline. Repeated PSG after CRT demonstrated a reduction in the duration of arterial oxygen desaturation<or=95% (251.2+/-36.7 vs 141.0+/-37.1 minutes), AHI (27.5+/-4.7 vs 18.1+/-3.0, P=0.05), and number of central sleep apnea (CSA) (7.8+/-2.6 vs 3.0+/-1.3/hour, P=0.03), but not number of obstructive sleep apnea (OSA, 8.6+/-3.3 vs 7.2+/-2.3/hour, P=0.65) compared to baseline. Percentage change in PASP was significantly correlated with percentage changes in LVEF (r=-0.57, P=0.04), AHI (r=0.5, P=0.05), and number of CSA episodes (r=0.55, P=0.02).
  
  
  CONCLUSIONS
  The results demonstrated that CRT significantly reduces CSA in patients with HF. Importantly, we have noted a decrement of PASP correlated to drop in CSA which maybe one of the mechanisms explaining this observation. Future studies are required to confirm our finding and elucidate other possible mechanisms in this regard.
authors.affiliation: Cardiology Division, Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong, China.
authors.forename: Kai-Hang
authors.initials: KH
authors.lastname: Yiu
authors.forename: Kathy Lai-Fun
authors.initials: KL
authors.lastname: Lee
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
authors.forename: Chung-Wah
authors.initials: CW
authors.lastname: Siu
authors.forename: Kin-Man
authors.initials: KM
authors.lastname: Miu
authors.forename: Bing
authors.initials: B
authors.lastname: Lam
authors.forename: Jamie
authors.initials: J
authors.lastname: Lam
authors.forename: Mary Sau Man
authors.initials: MS
authors.lastname: Ip
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000517:prevention & control*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D020182:Sleep Apnea, Central / Q000175:diagnosis* / Q000517:prevention & control*; D016896:Treatment Outcome