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Toronto (Nov. 9, 2005) - A novel, promising and simple therapy that significantly improves heart function and exercise capacity in patients with heart failure has been demonstrated in a multi-centre trial in 10 Canadian and one German centre.
Led by researchers at Toronto General Hospital of the University Health Network, this first ever randomized trial showed that treating central sleep apnea in heart failure patients with an easy-touse portable device called continuous positive airway pressure (CPAP) decreased nightly central sleep apnea episodes, increased oxygen levels during the night, improved heart function, and walking distances, while also reducing sympathetic nervous activity, which activates the stressful fight-or-flight response.
The results of this study are published in a paper entitled "Continuous Positive Airway Pressure for Patients with Central Sleep Apnea and Heart Failure", in the November 10, 2005 issue of The New England Journal of Medicine.
"We're trying to improve the outcomes of heart failure, a serious debilitating disease", said Dr. Bradley, the lead investigator of the study, and Head of the Sleep Research Laboratories at Toronto General Hospital, Mount Sinai and Toronto Rehabilitation Institute, and Director of the University of Toronto Centre for Sleep Medicine and Circadian Biology. "This study demonstrates that some heart failure patients could benefit from using CPAP, in that they could improve their level of activity and get back up on their feet since it improves heart function. However, we did not show that it improves survival."
It is estimated that central sleep apnea affects about a third of all patients with heart failure, a condition in which the heart does not pump as strongly as it should. More than 400,000 Canadians are affected by heart failure, and over 50,000 new cases are diagnosed each year. Moreover, despite major advances in treatment over the past 25 years, there have been only modest improvements in heart failure outcomes on a population-wide basis.
In central sleep apnea, (unlike the more well-known obstructive sleep apnea) the airway is not blocked, but the brain fails to signal the muscles to breathe due to instability in the respiratory control center. The results are short pauses in breathing, often as many as hundreds of times a night. These are accompanied by decreases in blood oxygen levels.
Continuous positive airway pressure (CPAP) is a treatment in which the patient wears a mask over the nose. An air blower forces air through the upper airway which is then transmitted to the lungs and around the heart. The air pressure is adjusted so that it is just enough to assist the heart in pumping and to reduce the frequency of breathing pauses during sleep. The pressure is constant.
Dr. Bradley and physicians in the other 10 centres examined 258 patients who had heart failure and central sleep apnea, with, on the average, 40 such episodes per hour during the night. Of these patients, 128 patients were randomly assigned to receive CPAP, while 130 did not. All patients continued their heart medication, and were followed for up to five years. During this time, sleep studies were conducted, and measurements of heart function, exercise capacity, quality of life, adrenaline levels and survival were performed.
Three months after being randomly assigned to each group, the patients who used the CPAP device had decreased their sleep apnea episodes by 50% compared to the patients who did not use CPAP; they also had a greater reduction in sympathetic nervous system activity. A reduction in sympathetic nervous system activity allows the heart to recover from being bombarded with adrenaline, which raises the heartbeat and blood pressure.
In addition, patients who received CPAP increased their nighttime oxygen levels, their exercise capacity and the efficiency with which their hearts were able to pump blood to the rest of the body. On average, the CPAP users were able to increase the amount of blood being pumped out with each contraction, by 9%. When the pumping action of the heart is improved, it allows a person's exercise capacity to increase. Consequently, the CPAP users were also able to walk 20 metres further on a standard six-minute walking test than individuals who did not receive CPAP. These improvements related to the use of CPAP were long lasting, and were sustained for at least 2 years.
The study did not show any differences in survival between the two groups of patients. However, it would be difficult to demonstrate survival effects with the relatively small number of patients enrolled in this study.
"We've demonstrated in this study that central sleep apnea contributes to impairment of heart function in patients with heart failure, and that a simple and specific therapy targeting central sleep apnea can improve heart failure," said Dr. Bradley. "Ultimately, given a larger study than ours with a sufficient number of patients, it may be possible that CPAP therapy might keep people out of the hospital, and improve their mobility and reduce death rates."
Dr. John Floras, lead cardiologist on the study, holder of the Canada Research Chair in Integrative Cardiovascular Biology, Director of Research for the UHN and Mount Sinai Division of Cardiology, and a Career Investigator of the Heart and Stroke Foundation of Ontario, was a co-investigator in the study. He emphasized that, "Unfortunately, there are as yet no cardiology guidelines on how to treat patients who have both heart failure and sleep apnea. Sleep apnea is one of the major risk factors for cardiovascular disease that neither the public or even physicians are aware of, but research is beginning to demonstrate that this is something we should be paying more attention to because identifying and treating sleep apnea may well reduce the impact of heart failure in our society. As the population ages, there will be an ever-growing number of patients with this illness."
A grant from the Canadian Institutes of Health Research (CIHR) University Industry Program in partnership with Respironics, ResMed and Tyco Healthcare; Sponsors had no role in the conception or design of the study, nor in the collection, analysis or interpretation of the data.
Toronto General Hospital is a partner in University Health Network, along with Toronto Western and Princess Margaret Hospitals. The scope of research and complexity of cases at Toronto General Hospital has made it a national and international source for discovery, education and patient care. It has one of the largest hospital-based research programs in Canada, with major research projects in transplantation, cardiology, surgical innovation, diabetes, infectious diseases, and genomic medicine. Toronto General Hospital is a teaching hospital affiliated with the University of Toronto.
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