By Will Boggs, MD
NEW YORK (Reuters Health) - Auto-servo ventilation (ASV) did not improve ejection fraction or quality of life in a new study of patients with sleep apnea and heart failure, researchers have found.
Sleep-disordered breathing (SDB) may affect between half and 71% of heart failure patients and contributes to increased mortality, according to their report, online December 6 in the European Respiratory Journal. But previous studies of ASV in these patients have yielded inconsistent findings.
Dr. Michael Arzt from University Hospital Regensburg, Germany, and colleagues tested whether additional treatment with ASV improves daytime cardiac function and quality of life in a randomized trial of 72 patients with congestive heart failure and SDB with no or mild SDB-related symptoms.
In the intent-to-treat analysis, the change in left ventricular ejection fraction (LVEF, the primary endpoint) was similar in the ASV group and in the control group (2.8% vs. 2.3%, respectively; p=0.767). Results were similar when patients with obstructive sleep apnea and central sleep apnea were analyzed separately.
ASV effectively suppressed SDB and contributed to non-significant declines in N-terminal pro brain natriuretic peptide (NT-proBNP) and increases in glomerular filtration rate. But there were no significant improvements in general or disease-specific quality of life.
The per-protocol analysis included 21 patients in the ASV group and 21 patients in the control group, and this analysis yielded somewhat different results. Improvements in LVEF did not differ between the ASV and control arms, but NT-proBNP levels declined significantly in the ASV group (372 ng/mL decrease) compared with controls (142 ng/mL increase).
Three of eight SF-36 subscores improved significantly in the ASV group, whereas there were no significant improvements in the disease-specific quality of life scores and the Fatigue Severity Scale of the Epworth Sleepiness Scale in the ASV group.
Sample size calculation suggested 35 patients per group would be required to detect a 4% improvement in left ventricular ejection fraction (LVEF).
"Although the present study is to date the largest randomized-controlled trial of ASV in congestive heart failure patients with SDB assessing cardiac function, the per-protocol analysis did not comply with the calculated sample size and the trial therefore lacked the necessary power to reliably address the effects on several of the outcome measures and to perform important subanalyses such as whether effect sizes depend on age or cause of heart failure," the researchers note.
"However," they conclude, "a stepwise trend towards greater improvements in glomerular filtration rate, general quality of life (physical component score), and fatigue in the group of patients who complied with ASV therapy, suggest that these outcomes should be re-evaluated in larger trials."
The ventilation systems used in the study came from Philips Respironics, and Philips Home Healthcare Solutions supported the work.
Dr. Arzt said two large studies are on the way -- ADVENT-HF and Serve HF -- and will be able to detect smaller effects than the current trial.
"I hope that someday treatment of sleep-disordered breathing (SDB) in heart failure will be recognized as a non-pharmacological adjunct in heart failure therapy," he told Reuters Health by email. "There is still a long road to go."
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