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Daytime and Night-Time Central Apneas in Heart Failure
Study Questions:
What is the occurrence and prognostic significance of night-time, daytime, and 24-hour central apneas (CAs) in systolic heart failure (HF)?
Methods:
The study cohort was comprised of 525 systolic HF patients (American College of Cardiology/American Heart Association [ACC/AHA] stage C, left ventricular ejection fraction [LVEF] 33 ± 9%, age 66 ± 12 years, males 77%) on stable (≥3 months) guideline-recommended therapy for HF. Exclusion criteria were severe pulmonary or neurological disease; thyroid dysfunction; or concurrent therapy with morphine or derivatives, theophylline, oxygen, benzodiazepines, acetazolamide, continuous positive airway pressure, or servoventilation. The cohort underwent prospective evaluation for apnea, including 24-hour respiratory recording, and were followed up using cardiac mortality (sudden death, progressive HF-related death, or acute myocardial infarction) as an endpoint.
Results:
The study authors found that 24-hour prevalence of predominant CAs (apnea/hypopnea index [AHI] ≥5 events/hour, with CA >50%) was 64.8% (night-time 69.1%, daytime 57.8%), while prevalence of predominant obstructive apneas (OAs) was 12.8% (AHI ≥5 events/hour with OAs >50%: night-time 14.7%, daytime 5.1%). AHI ≥15 events/hour were 49.8% and 28.2%, respectively. The authors reported that CAs were associated with activation of the neurohormonal system, ventricular arrhythmic burden, and systolic/diastolic dysfunction (all p < 0.05). Fifty cardiac deaths occurred during the median 34-month follow-up period (interquartile range, 17-36). Night-time, daytime, and 24-hour moderate-severe CAs were associated with increased cardiac mortality (AHI < / ≥ 15, log-rank, 6.6, 8.7, 5.3; all p < 0.05, central apnea index [CAI] < / ≥ 10, log-rank 8.9, 11.2, 10.9; all p < 0.001). Nonsurvivors were older (73 ± 9 years vs. 65 ± 12 years; p = 0.001), more symptomatic (New York Heart Association class III-IV: 56.0% vs. 32.2%; p = 0.001), and showed lower LVEF (29 ± 9% vs. 32 ± 9%; p = 0.01), reduced estimated glomerular filtration rate (44 ± 15 ml/min vs. 68 ± 26 ml/min; p = 0.001), and higher plasma N-terminal pro–B-type natriuretic peptide (NT-proBNP) level (5475, 2747-9596 ng/L vs. 1197, 461-2719 ng/L; p = 0.001). Independent predictors of outcome included age, BNP level, renal dysfunction, 24-hour AHI, CAI, and time with oxygen saturation <90%.
Conclusions:
The study authors concluded that in systolic HF patients, CAs occur throughout the 24-hour period, and are associated with a neurohormonal activation, ventricular arrhythmic burden, and worse prognosis.
Perspective:
Although the brain is only about 2% of the total body weight, it receives 15-20% of the body's blood supply and therefore is most likely to be affected in HF. This is an important study because it suggests that a more comprehensive evaluation of CA may be required if we have to develop effective therapies for CA associated with HF.
Keywords: Acetazolamide, Arrhythmias, Cardiac, Benzodiazepines, Cardiac Surgical Procedures, Continuous Positive Airway Pressure, Death, Sudden, Diastole, Geriatrics, Heart Failure, Heart Failure, Systolic, Morphine, Myocardial Infarction, Natriuretic Peptide, Brain, Renal Insufficiency, Sleep Apnea, Central, Sleep Apnea, Obstructive, Stroke Volume, Systole, Theophylline, Thyroid Diseases
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