Cardiology & Sleep Medicine

Medical research has shown a link between sleep-disordered breathing and hypertension(1, 2), a condition that often leads to other cardiovascular diseases, such as heart failure. Hypertensive heart disease is the leading cause of illness and death from hypertension. It affects approximately 7 out of 1,000 people(3), or roughly 2.5 million Americans. In addition, patients suffering from ischemic heart disease, chronic heart failure (CHF) and cerebrovascular disease are also at risk(4).

Findings in a large international study(5) linked more than 90% of heart attacks to a few easily measured risk factors common to essentially every region and ethnic group around the world. Two of those leading factors are high blood pressure and obesity, the chief risk factor for OSA(6) . These findings add to the mounting evidence of the rising global burden of cardiovascular disease, where in some developing countries has now eclipsed infectious disease as the most important cause of death.

In the United States hypertension affects 50 million Americans and OSA is a primary identifiable cause(7). There is an extremely high correlation of OSA in this population exceeding 50%(8, 9). Additionally, patients with OSA are three times more likely to have heart failure(10). Studies on patients with hypertension, when effectively treated with Continuous Positive Airway Therapy (CPAP) therapy show a decrease in blood pressure within 24 hours(11). CPAP also reduces angina and ST segment depression during sleep and augments heart rate variability during the day(12). A recent study(13) also tracked 72,000 nurses and determined that women who averaged five hours or less of sleep a night were 40% more likely to develop heart disease than women who got eight hours. Such research suggests that getting enough sleep may be nearly as important as eating right and exercising, 2 of the 20 most important preventive factors in avoiding a heart attack.

The Missed Opportunity

What has been preventing cardiology and sleep medicine from taking advantage of this enormous opportunity? Some of the reasons are not so obvious:

• Cardiologists receive virtually no training in sleep medicine in their residencies and therefore are not trained in the co-morbidities associated with SDB. Additionally, until recently there has been a limited body of peer review literature in respected cardiology periodicals.
  
  
• Traditionally cardiologists and pulmonologists (the primary sub specialty associated with sleep medicine) have very little interaction, or overlap, in their practices.
  
  
• Cardiologists have been referred to as the most entrepreneurial group of physicians around. In order for them to consider a change in their practice, they must be convinced of a strong incremental economic, as well as clinical benefit. This economic benefit needs to meet a very simple test - does it provide the cardiologist with a benefit of $400 per effort hour?
  
  
• Cardiologists are not referral happy, they like holding onto their patients for as long as possible. Aggressive referral to sleep labs goes against this pattern.
  
  
• While the sleep community understands that there is a great opportunity in the cardiologist market, they have been unsuccessful in developing this new frontier.
  
  
• The clinical features of OSA in CHF patients are similar to those of OSA patients with normal left ventricular function. Patients are usually obese and have a history of loud and habitual snoring. However, only a minority complain of excessive daytime sleepiness, suggesting that many CHF patients with OSA have relatively asymptomatic OSA(15), and as mentioned earlier there is a higher than normal prevalence of mixed central and obstructive disease.
  
  
• The majority of cardiology patients are over 65, marking them as a generally more challenging patient population. They tend to represent a relatively modest percentage (10%-25%) of the patient population being tested and treated for OSA today. Sleep labs are not generally familiar with this added level of complexity and tend to do poorly, in terms of patient satisfaction. On the other hand, cardiology practices are extremely good at satisfying their patient's needs and foster a much higher level of trust and confidence.
  
  
• No one likes the therapeutic option for OSA - CPAP. Furthermore, CPAP compliance among the general population is estimated to be less than 50%. Assuming that this population is more difficult one can assume that compliance in this group would be even less, creating problems for the cardiologist.
  
  
• Cardiology office staff, like most family practice staff, is not trained in "spotting" potential sleep problems. They are busy enough as it is and can't seem to find the time to add an additional responsibility to their tasks, such as taking the time to screen patients for OSA.

Heart Failure is Prevalent, Deadly and Expensive

CHF Statistics (US Market)

SOURCE: American Heart Association

Summarizing these barriers we find that the major obstacles to cardiologists integrating a sleep program into their practice are:

• There's limited economic incentive
  
  
• They do not want to lose control of their patients to another specialty
  
  
• They are not trained in sleep medicine and may not fully comprehend the benefits of treating OSA effectively in his patient population
  
  
• The staff cannot take on any additional burdens
  
  
• The poor state of CPAP titration and compliance is a risk to the practices' patient satisfaction
  
  
• Concern over the political backlash of being seen as a competitor to local Pulmonary practices
  

REFERENCES

1 Bradley T, Floras J Sleep apnea and heart failure Circulation 2003; 107:1671-1678
2. Peppard PE, Young T, Palta M et al Prospective study of the association between sleep disordered breathing and hypertension N Engl J Med 2000:342:1378-1384
3. Medline OnLine Medical Dictionary; http://www.nlm.nih.gov/medlineplus/ency/article/000163.htm
4. Sinn DD, Fitzgerald F, Parker JD et al Relationship of systolic blood pressure to obstructive sleep apnea in patients with congestive heart failure Chest 2004
5. Interheart study; Salim Yusuf, McMasters University August 2004
6. Horner RL, Mohiaddin RH, Lowell DG et al. Sites and sizes of fat deposits around the pharynx in obese patients in obese patients with obstructive sleep apnea and weight matched controls. Eur Respir J 1989:2:613-622
7. Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure
8. Sinn DD, Fitzgerald F, Parker JD et al Risk factors for obstructive and central sleep apnea in 450 men and women with congestive heart failure. Am J Respir Crit Care Med 1999 160:1101-1106
9. Javaheri S, Parker TJ, Limming JD, et al. Sleep apnea in 81 ambulatory male patients with stable heart failure: types and their prevalences, consequences and presentations. Circulation 1998 97:2154-2159
10. Shahar E, Whitney EW, Redline S et al, Sleep disordered breathing and cardiovascular disease: cross sectional results of the sleep heart health study.Am Jour Resp Care Med 2001; 163:19-25
11. Dyugovskaya L, Lavie P, Lavie L, Increased adhesion molecule expression and production of reactive oxygen species in leukocytes of sleep apnea patients. Am J Respir Crit Care Med 2002 165;934-939
12. Ip MS, Lam B, Chan LY et al Circulating nitric oxide is suppressed in obstructive sleep apnea and is reversed by nasal continuous positive airway pressure Am J Resp Crit Care Med 2000:162:2166-2177
13. Ayas, Najib; Archives of Internal Medicine January 2004
14. Thomas R, Daly R, Weiss JW Low concentration carbon dioxide is an effective adjunct to positive airway pressure in the treatment of refractory mixed central and obstructive sleep disordered breathing Journal SLEEP paper accepted week of September 13, 2004
15. Bradley T, Floras J Sleep apnea and heart failure Circulation 2003; 107:1671-1678
16. Sleep Heart Health Study, 2004

< Return to Research Index