A 75-year-old man with ischemic cardiomyopathy is hospitalized with acute decompensated heart failure. His left ventricular ejection fraction is 10% and he has not been compliant with his medications.
His blood pressure is 134/78 mm Hg, pulse is 68/min, respirations are 20/min, and oxygen saturation is 96% on 2-liters O2 by nasal cannula. His BMI is 24 kg/m².
The patient's symptoms improve with intravenous furosemide therapy and he appears comfortable at rest on supplemental oxygen. During the night, the nurse notes frequent episodes of desaturation accompanied by short runs of nonsustained ventricular tachycardia.
Which of the following is the most likely diagnosis?

Question

Quizplus · Accepted Answer

Frequent episodes of nocturnal hypoxemia in a patient with normal BMI and advanced heart failure (HF) suggest possible central sleep apnea (CSA). Heart failure leads to increased left ventricular (LV) filling pressure and resultant pulmonary congestion. This activates pulmonary vagal irritant receptors, leading to hyperventilation and hypocapnia. Superimposed arousals cause further increases in ventilation and drive PaCO₂ below the threshold for ventilation, resulting in a central apnea. The apnea persists until PaCO₂ rises above the threshold required to stimulate ventilation. CSA in HF is sustained by recurrent arousals due to apnea-induced hypoxia and the increased effort to breathe during the ventilatory phase as a consequence of pulmonary congestion and decreased lung compliance. CSA in HF is characterized by Cheyne-Stokes breathing, a crescendo-decrescendo oscillation of tidal volume, with intervals of hyperventilation separated by periods of hypopnea and apnea. Polysomnography is the gold standard test for diagnosis of sleep-disordered breathing. Treatment includes optimal medical management of heart failure, positive airway pressure therapy, and supplemental oxygen. (Choices B and C) Electrolyte or acid-base abnormalities can cause atrial or ventricular arrhythmias; however, they would not be expected to cause nocturnal hypoxemia. (Choices D and E) Neuromuscular disease can cause episodic hypoxemia due to poor respiratory effort. Similarly, obstructive lung disease can also cause hypoxemia due to a combination of airflow limitation and impaired gas exchange. This patient has no history of these conditions. Educational objective: Central sleep apnea with Cheyne-Stokes breathing is a potential complication in patients with heart failure. Treatment includes positive airway pressure therapy and supplemental oxygen. __________ References: The relationship between nocturnal hypoxemia and left ventricular ejection fraction in congestive heart failure patients. (http://www.ncbi.nlm.nih.gov/pubmed/24693442) Sleep disordered breathing in patients with acutely decompensated heart failure. (http://www.ncbi.nlm.nih.gov/pubmed/18614398) Cardiac arrhythmias and sleep-disordered breathing in patients with heart failure. (http://www.ncbi.nlm.nih.gov/pubmed/25325536)

A 75-Year-Old Man with Ischemic Cardiomyopathy Is Hospitalized with Acute