Sleep disordered breathing (SDB) and heart failure (HF) are inextricably linked. Obstructive sleep apnea (OSA) is highly prevalent and is associated with adverse outcomes in patients with HF. Another type of SDB – central sleep apnea (CSA) – is predominantly found in the HF population. Despite less incidence and prevalence when compared to OSA, and smaller incidence and prevalence within the HF population, there is a resultant two-fold increase in mortality compared to those patients without CSA and HF.
The most common form of sleep apnea, OSA is caused by a blockage of the airway by the tongue or other pharyngeal issues. OSA often causes loud snoring. In contrast, CSA is not caused by an airway blockage. In CSA, the brain does not signal the diaphragm to initiate a breath. Breathing repeatedly stops and starts during sleep. Most notably, CSA does not cause snoring. Most heart failure patients have a combination of both types of sleep apnea, termed mixed-complex sleep apnea.
“The overall prevalence of SDB among patients with symptomatic heart failure is 40 to 60 percent, with OSA making up approximately one third of the cases,” says Sandra A. Carey, PhD, MPH, ANP-BC, FHFSA, advanced nurse practitioner at the Center for Advanced Heart and Lung Disease at Baylor University Medical Center in Dallas, TX, part of Baylor Scott & White Health. “Many studies involving patients with heart failure reported roughly equal proportions of OSA and CSA in combination. However, in a meta-analysis of 2,570 patients with heart failure with reduced ejection fraction and moderate to severe sleep apnea, CSA represented the dominant phenotype in more than 70 percent of cases.”
SDB negatively affects cardiac output in multiple ways, including increased right ventricular (RV) venous return, increased pulmonary artery vasoconstriction and pulmonary hypertension, RV distension, diastolic leftward septal shift, impaired left ventricle (LV) filling, decreased LV preload and stroke volume, and increased LV afterload.
The link between sudden cardiac death, sleep apnea and heart failure
A 2005 retrospective study found that the relative risk of sudden cardiac death (SCD) was almost 2.6-fold higher between midnight and 6 a.m. in patients with OSA, compared to the general population. This relative risk of SCD increased in proportion to the increasing severity of the apnea hypopnea index (AHI), a number that represents the average number of apneas and hypopneas a patient experiences each hour of sleep. Twelve risk factors overlap between SCD and OSA. These include advanced age, heart failure, male sex, family history, coronary artery disease, women who are postmenopausal, obesity, prolonged QT interval, decreased heart rate variability, diabetes and dyslipidemia.
“This is a very complicated phenomenon,” Dr. Carey says. “If a patient has uncontrolled hypertension, he or she probably has sleep apnea. If a patient has Afib, we probably need to be discussing the possibility of a sleep apnea diagnosis. This is also where we need to be partnering with our sleep medicine colleagues in screening patients for sleep apnea. There is a huge deficit of sleep physicians in the United States, thus sharing the responsibility would be helpful, especially when most of the population of the most severe sleep apnea patients are our heart failure patients.”
Screening patients for sleep apnea
In 2021, the American Heart Association (AHA) issued a scientific statement on OSA and cardiovascular disease. Signs and symptoms of OSA include excessive daytime sleepiness, morning headaches, memory impairment, difficulty concentrating, irritability and/or changes in affect, nocturia and erectile dysfunction. Exam findings include obesity, increased neck circumference and craniofacial abnormalities.
The AHA recommends screening for OSA when patients have resistant/poorly controlled hypertension,
pulmonary hypertension, and/or recurrent atrial fibrillation (after either cardioversion or ablation). Physicians should consider a sleep study if concerning signs or symptoms of sleep apnea are present:
NYHA class II-IV HF symptoms, tachy-brady syndrome, sick sinus syndrome, ventricular tachycardia, survivors of sudden cardiac death or stroke.
The American Academy of Sleep Medicine also recommends an annual OSA screening for all adult patients who have heart failure, elevated blood pressure, atrial fibrillation, resistant hypertension, type 2 diabetes or stroke.
“All of these comorbidities continue to exacerbate each other,” Dr. Carey says. “It is especially important for patients in high-risk groups to be screened using a validated OSA questionnaire (e.g. STOP-BANG or Berlin) because sleep apnea hurts hearts. It should be an integral part of the cardiology consultation, either inpatient or outpatient.
Research in sleep disorders in advanced heart failure
Although there is an extreme paucity of data in this patient population, advanced heart failure clinicians have made some notable inroads through Baylor Scott & White Research Institute. “The Effect of OSA on 3-Year Outcomes in Patients who Underwent Orthotopic Heart Transplantation” was published in The American Journal of Cardiology July 2019. This was the largest cohort of its kind published to date.
“We found some compelling results,” Dr. Carey says. “Patients with untreated OSA were at three times the risk of developing late graft dysfunction than those with treated OSA or those who did not have the condition at all. Because OSA is a common co-morbidity of orthotopic heart transplant patients, screening for and treating OSA should occur during the heart transplant selection period.
“There is a big myth that heart transplant eradicates sleep apnea,” Dr. Carey continues. “This is absolutely not true, and I would argue that it can exacerbate sleep apnea in certain patients. We all know that most patients on steroids gain weight, and they don’t get it off very easily, if at all. And some transplant patients are maintained on steroids, or some go back to bad habits they had before transplant.”
Because patients frequently resist undergoing in-lab sleep tests, the BSW researchers conducted a trial of a home sleep test. This trial was the first time any group has used this test specifically in the advanced heart failure population. The study was stratified between ventricular assist device (VAD) patients and heart failure patients post transplant. The research team quickly discovered the test was ineffective in VAD patients. This was due to the patients not having a pulse, which is required to obtain the data to make the diagnosis. However, it was very successful in the HF and post cardiac transplant patient cohorts.
“Home sleep testing does have its critics, but if a patient can do their test at home, they are more likely to do it,” Dr. Carey says. “The test is FDA approved for OSA, and it also helps to identify CSA. We’ve shown that home sleep apnea testing is a feasible and effective tool for screening and diagnosis of sleep apnea in advanced heart failure patients. It’s a win-win for everyone.”
Alternatives to continuous positive airway pressure support (CPAP)
Continuous positive airway pressure (CPAP) support can be very helpful for many patients; however, many patients cannot tolerate the CPAP machine. CPAP presents a host of problems, including tooth erosion, skin irritation, dryness, pain, infection, device noise and claustrophobia. Fortunately, new devices offer alternatives to CPAP.
For patients with CSA, phrenic nerve stimulation can be an option. In this therapy, an implantable device stimulates the phrenic nerves to contract the diaphragm, pulling air into the lungs. The device turns on automatically and continuously monitors and stabilizes breathing.
Patients with OSA may undergo hypoglossal nerve stimulation. A device is implanted through two small incisions, including one in the upper chest for the battery and breathing sensor. The stimulator itself is placed under the jaw around the nerve to the tongue. The goal of this surgical option is to link the patient’s breath with the tongue so that, with each breath, the stimulator forces the tongue and throat muscles to open, thus alleviating the obstruction.
“The prevalence of sleep apnea remains exceedingly high in both patients with heart failure and post heart transplant patients,” Dr. Carey says. “This adds a significant and ominous high-risk co-morbidity that will continue to facilitate poor short- and long-term clinical outcomes in both cohorts. We must continue to focus on appropriate screening and diagnosis of patients, patient education and research into promising therapies for sleep apnea.”
