by Alan D. Steljes, MD, FACC, FRCPC
Case Report
A 68 year-old male complains of progressively limiting shortness of breath with exertion. He is occasionally awakened at night with shortness of breath which forces him to sit up. On exam, he is obese. Neck veins are distended. Heart sounds are slightly muffled. Fine crackles are heard at both lung bases. Mild swelling in both ankles. Ultrasound of the heart shows mild dilatation of the left ventricle with global reduction of systolic function. Ejection fraction: 35% (normal is 50 to 70%). The clinical diagnosis is congestive heart failure with reduced ejection fraction.
Introduction
Congestive heart failure (CHF) is a common disorder which leads to progressive disability and ultimately death. Medical management of CHF is one of the big success stories in cardiology. However, even optimally managed patients may have untreated sleep disordered breathing (SDB) which adversely affects their prognosis. Effective evaluation and management of SDB unlocks significant gains.
What is Congestive Heart Failure?
There are two components to the syndrome. Congestion from excessive fluid retention is responsible for most of the patients’ symptoms. Systemic congestion causes swelling in the legs but may later progress to the abdomen or liver. Congestion in the lungs causes shortness of breath which worsens when the patient lies down due to a shift of fluid from the legs to the chest.
Heart failure is the second component and refers to the impairment of the heart’s ability to deliver sufficient blood flow to the other organs. Exertion is limited due to fatigue or shortness of breath.
Causes of Congestive Heart Failure
The function of the heart is to circulate blood (with nutrients and oxygen) to the skeletal muscles and to other organs. Any of several diverse conditions can cause CHF. Most commonly these are conditions that affect the left ventricle (LV), the main pumping chamber in the heart. With each heartbeat, the LV fills with oxygenated blood from the lungs, then it squeezes or contracts to eject blood into the bloodstream. Damage to the heart muscle (due to heart attack or a muscle disease known as cardiomyopathy) impairs the ability of the chamber to contract and eject blood. The “ejection fraction” of the left ventricle is reduced leading to the designation of CHF with reduced ejection fraction (HFrEF.)
Other patients may have CHF with preserved ejection fraction (HFpEF.) Pumping of the heart is normal but refilling of the LV between heartbeats is impaired.
Once CHF is established, it tends to be progressive due to activation of various neural and hormonal pathways.
Mechanisms Underlying CHF and SDB
About 50% of patients have moderate to severe obstructive sleep apnea (OSA). Untreated OSA leads to significant drops in oxygen levels and secondary activation of the sympathetic nervous system, both of which may provoke CHF.
However, CHF can also provoke OSA. Congestion within the pulmonary veins diminishes the upper airway size. This effect worsens when the patient is supine, due to fluid shifts from the lower extremities.
Many patients with reduced ejection fraction additionally have central sleep apnea (CSA). The mechanisms are complex and involve deficiencies in the negative feedback system which controls breathing. It is important for physicians who report sleep studies to characterize apneas as either central or obstructive in origin. Failing to do so may underestimate the severity of central sleep apnea and lead to errors in therapy.
Untreated OSA leads to significant drops in oxygen levels and secondary activation of the sympathetic nervous system, both of which may provoke CHF.
Treatment of CHF
General measures include dietary changes and exercise; avoidance of alcohol and smoking.
Commonly prescribed medications include furosemide, spironolactone, carvedilol, and Sacubitril/valsartan in addition to a SGLT2 inhibitor such as empagliflozin.
The aim of medical therapy is to control congestion and relieve symptoms but also to block those deleterious neural and hormonal pathways which lead to progression of CHF.
Pacemakers or defibrillators may be needed for advanced CHF patients to coordinate the function of the left and right ventricles and to prevent sudden death.
Once medical therapy is optimized, patients should be screened for sleep apnea, recognizing that identifying and treating coexistent sleep apnea can have a major impact on patients’ well-being.
Treatment of Sleep Disordered Breathing in CHF
The treatment of choice for CHF with obstructive sleep apnea is CPAP. The benefits are well documented. Patients typically feel better. Objectively, there may be improvement in left ventricular function, reduced need for hospitalization, and potentially improved survival. Patients who are intolerant of CPAP may be managed with oral appliance or a hypoglossal nerve stimulator (may not be indicated if a pacemaker or defibrillator is in place).
The optimal management of central sleep apnea remains unclear.
Therapy generally starts with a trial of CPAP which can be effective for both OSA and CSA in some patients.
Persistent central sleep apnea is problematic. More advanced positive airway pressure protocols can be effective. However, the Serve-HF randomized trial of Adaptive Servo Ventilation (ASV) versus optimal medical therapy indicated excess cardiovascular mortality within the treatment group. This unexpected outcome may have been related to the particular algorithm used in the trial. However, we remain cautious about this therapy in patients with an ejection fraction < 45%.
Low flow nocturnal oxygen is another option.
More recently, an implanted phrenic nerve stimulator has had impressive results and may be used more frequently as clinical experience increases.
Future Considerations
The frequency of congestive heart failure is increasing steadily. It is estimated that by 2030 there will be 8 million patients afflicted in the United States – equivalent to almost 3% of the adult population. Earlier management of sleep apnea could be helpful to slow this trend.
For example, there are an estimated 20 million people in the US who have a reduced left ventricular ejection fraction but who have not yet developed CHF. Half of these patients have undiagnosed OSA. Current protocols correctly emphasize management of hypertension to prevent progression to CHF but do not address sleep apnea.
Undertreatment of OSA is not just an issue with CHF but is true for other cardiovascular diseases. The problem is that sleep medicine has not yet proven the value of treatment of sleep apnea to the standard required for inclusion in cardiology clinical guidelines. In fairness, randomized clinical trials have been notoriously difficult to perform. The biggest challenge is the underwhelming adherence rates with CPAP, our most commonly prescribed therapy. Adherence should improve with better patient follow-up in specialized clinics. New technologies including remote patient monitoring and improved comfort of PAP therapy (perhaps KPAP) should have an impact. Oral appliances tend to have better long-term compliance but are also lacking in long-term efficacy studies.
Conclusion
Sleep disordered breathing is commonly associated with CHF. There is likely a bidirectional relationship between the two conditions with congestive heart failure exacerbating upper airway obstruction and obstructive sleep apnea, in turn, exacerbating cardiac function.
CPAP is an effective therapy which may improve heart function beyond medication alone. Oral appliance therapy is a good alternative for patients who do not tolerate CPAP.
Central sleep apnea may also be seen in patients with CHF. Mechanisms are complex and optimal management of CSA remains to be determined.
Alan D. Steljes, MD, FACC, FRCPC was trained as an interventional cardiologist. Since fellowship, he has obtained additional certification in nuclear cardiology, echocardiography, CT coronary angiography and finally sleep medicine. In 2010, he opened a two bed sleep lab, recognizing the heart-sleep apnea interaction. The initial 2 beds have been scaled up to 12 beds since associating with the Nevada Heart & Vascular Center. He has since retired from the cardiology practice but continues to oversee the sleep program. He remains passionate about spreading the word about sleep disordered breathing and the heart. He currently shares his time between Las Vegas, NV and Mount Pleasant, SC.