The ever-increasing evidence linking obstructive sleep apnea (OSA) to cardiovascular conditions has spurred cardiologists to form multidisciplinary teams to better treat their patients suspected of having OSA.
What we know
“The medical profession as a whole over the last 15 years was relatively unaware of the implications of sleep apnea,” says Virend K. Somers, MD, PhD, director of the Sleep and Cardiovascular Clinical Research Units at the Mayo Clinic in Rochester, Minn. Somers was the lead author of an expert consensus document on OSA, spearheaded by the American Heart Association and the American College of Cardiology (J Am Coll Cardiol 2008;52:686–717).
In the document, Somers and colleagues agreed that much needs to be learned about the relationship between OSA and cardiovascular events. They concluded that a “relative lack of definitive outcomes data to guide clinical practice necessitates a highly individualized approach to evaluation and management of those patients with comorbid cardiovascular disease and sleep apnea.”
In an effort to further outcomes data, Julio A. Chirinos, MD, director of noninvasive cardiac imaging at the Philadelphia VA Medical Center, is the chief investigator in the enrolling COSA (Cardiovascular Effects of Obstructive Sleep Apnea) study. The research is examining whether treatment of OSA with continuous positive airway pressure (CPAP) decreases heart disease risk factors, including inflammation (C-reactive protein) and insulin resistance. Researchers also are analyzing DNA to look for an association between apoE genotypes and both dyslipidemia and inflammation.
Patients will be randomized to CPAP alone, weight loss alone or a combination of the two therapies. "We know there is a risk of cardiovascular disease when someone has OSA. We don't yet know whether those risk factors will decrease if we treat the apnea," Chirinos says.
OSA affects more men than women and remains undiagnosed in 80 percent of patients. As the evidence of the potential harm of sleep apnea accrues, more cardiologists have begun working with other specialists to recognize and treat OSA early. In 2008, Desert Cardiology in Tucson, Ariz., added a certified sleep center and a pulmonologist to the practice after it realized just how many of their cardiology patients exhibited signs of sleep apnea or had been previously diagnosed with the disorder. “If you have a soft modicum of suspicion and ask the right questions, you can discover in your own practice those who should be tested,” says Greg Koshkarian, MD, a cardiologist with the group, who sees an estimated 300 patients per month. Of those 300, sleep studies are ordered for 5 to 10 percent. The addition of the sleep center has provided better patient care, he says.
Koshkarian calls a full sleep study in a lab the “gold standard” because it records brain waves, heart waves, chest wall movements, oxygen saturation and rapid eye movement. Not all patients are candidates for lab study, however, and sleep specialists are increasingly sending patients home with portable testing monitors.
BlueSleep, a sleep apnea center in downtown Manhattan, uses a portable Holter-oximeter device to diagnose patients in their home, says Jordan C. Stern, MD, founder and director of the center. Compared to a sleep lab that is equipped with a fixed number of beds, home sleep testing allows staff at the center to test a larger number of patients—three to 10 per week, says Stern.
Sam Kuna, MD, chief of the pulmonary, critical care and sleep section at the Philadelphia VA, also sends patients home with a portable device. “For our sleep apnea patient population, we feel quite comfortable that home testing and in-lab testing are equivalent,” he says. In fact, Kuna presented a study at the 2010 American Thoracic Society meeting showing no difference between the two approaches.
Kuna and colleagues evaluate about 50 patients a month for sleep apnea via home monitors. Many of his referrals come from Chirinos. “I would not consider sending my patients home with a sleep monitor. I leave that up to a qualified sleep specialist, whether he or she wants to perform in-lab testing or home testing,” Chirinos says.
The VA uses a type III portable monitor to record patients’ respiratory signals. This monitor allows Kuna to distinguish