Sleep-apnea prevalence in HF exceeds 50% in series; screening urged

September 14, 2004

Toronto, ON - More than half of patients with HF of various etiologies who were prospectively screened for sleep-related breathing disorders were found to have either central or obstructive sleep apnea in a series reported here at the Heart Failure Society of America 2004 Annual Scientific Meeting. Many more HF patients had milder breathing disorders, while fewer than a third had normal sleep studies.

Dr Barbara Lamp

Sleep apnea is widely underappreciated as a cardiovascular risk factor, a treatable one that primary-care physicians should consider on par with dyslipidemia and hypertension, according to Dr Barbara Lamp (Heart and Diabetes Center North Rhine Westfalia, Bad Oeynhausen, Germany). As such, screening for it should be part of the routine evaluation of patients with HF, she told heartwire .

In fact, "as sleep-disordered breathing has a major impact on prognosis and the deterioration of any cardiovascular disease, it may be worthwhile screening any cardiovascular patient, right from the beginning," Lamp said. She pointed to data suggesting that obstructive sleep apnea not only causes hypertension but also promotes insulin resistance and increases coagulation parameters. "It's a risk factor for progression of cardiovascular disease."

Of 440 unselected consecutive patients with NYHA class 2 to 4 HF and LVEF <50%, Lamp and her colleagues observed, the vast majority demonstrated some form of breathing disorder when monitored during sleep. Fully 53% had central or obstructive sleep apnea.

Incidence of sleep-related disorders in 440 consecutive patients with HF

Sleep-related disorder

Incidence (%)

Central sleep apnea

25

Obstructive sleep apnea

28

Milder sleep-related disorders

18

No sleep-related disorder

29
 
It may be worthwhile screening any cardiovascular patient, right from the beginning.

 

The "most amazing" observation in the study, according to Lamp, was that sleep apnea was common in a wide spectrum of HF severity. "And these patients were not too sicktheir mean NYHA class was about 2.5, and their peak VO2 was 15.5 [mL/kg per min]."

Central sleep apnea, observed Lamp, is probably "a marker for heart-failure severity." In the current series it was associated with increased LV end-diastolic diameter and decreased functional status. "So in heart-failure patients, it might be worthwhile looking for central sleep apnea because you might be able to stratify them into a low- or high-risk group or monitor therapeutic interventions like [cardiac resynchronization therapy] or beta blockade."

Blood gases and other features, central sleep apnea vs no sleep-related disorder

Parameter

Central sleep apnea (n=110)

No sleep-related disorder (n=130)

NYHA

2.7 2.4

LVEDD (mm)

7.1 6.4

Peak VO2 (mL/kg/min)

14.9 17.2

Peak CO2 (mm Hg)

33.6 36.7

All differences, p<0.05
LVEDD=left ventricular end-diastolic diameter

 
We would not need a full sleep-lab study on these patients, which would make things too expensive.
 

Measuring airflow alone isn't sufficient for sleep-apnea screening because it won't differentiate between the central and obstructive forms of the disorder, which are treated differently, Lamp observed. Screening in clinical practice might resemble what her group did in the current series, which was to assess peak VO2, blood gases, and muscle movements related to breathing along with the ECG.

"We would not need a full sleep-lab study on these patients, which would make things too expensive," Lamp said. "There are different Holter-like tools on the market that record airflow; some of them record oxygen saturation, some of them record thoracic and abdominal movements, some of them record ECGs."

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