SERVE-HF: What does it mean for cardiac rehabilitation?

Abstract

This editorial describes the impact of the results of the SERVE-HF study for cardiac rehabilitation as heart failure and sleep apnoea in cardiac rehabilitation patients is very common. Sleep apnoea is an independent risk factor for cardiovascular diseases. The most prevalent type of sleep apnoea is obstructive sleep apnoea (OSA), contributing to 38,000 cardiovascular deaths every year. Myocardial damage is thought to occur secondary to increased sympathetic activity, heart rate variability, endothelial dysfunction, systemic inflammation, oxidative stress, platelet activation and/or metabolic abnormalities. OSA represents a significant, but modifiable, risk factor for cardiovascular disease. However, OSA appears to be under-diagnosed in patients with coronary artery disease. Data from the Reha-Sleep registry suggest that the prevalence of sleep apnoea in patients attending cardiac rehabilitation facilities could be as high as 33%, and that there are few differences between patients with and without sleep apnoea with respect to sleep quality and daytime sleepiness. The prevalence of heart failure in western countries is about 1–2% of the adult population, with significant increases with age. Recent guidelines differentiate between heart failure due to reduced systolic left ventricular ejection fraction (HF-REF) and heart failure with preserved ejection fraction (HF-PEF) and impaired diastolic function. HF-REF is the most widely investigated and best understood type of heart failure, with a high prevalence in men with ischaemic heart disease. In contrast, HF-PEF is more prevalent in women and often has a non-ischaemic aetiology. Epidemiological data suggest that HF-REF and HF-PEF have a similar prognostic impact. A number of comorbidities have been linked to the development and progression of heart failure. One that is gaining increasing recognition is sleep-disordered breathing (SDB) with predominant OSA or central sleep apnoea (CSA) with or without Cheyne–Stokes respiration (CSR). CSR occurs when arterial carbon dioxide partial pressures fall below the apnoeic threshold. The cycle length of alternating periods of hypocapnia induces apnoea and reflex hyperventilation. CSR is inversely proportional to cardiac output and thus directly related to the severity of heart failure. A reduced left ventricular function delays the circulation time between the lungs and the chemoreceptors and increases the sensitivity of chemoreceptors, especially to carbon dioxide. The degree of carbon dioxide hypersensitivity is a major determinant of CSR. Small studies published to date have reported that the prevalence of SDB was almost 70–80% in patients with HF-PEF and up to 76% in those with HF-REF based on a cut-off of an apnoea–hypopnoea index (apnoeas and hypopnoeas per hour; AHI) 5/hour while moderate to severe sleep apnoea with an AHI 15/hour was prevalent in about half of the patients. SDB in general, as well as OSA and, in particular, CSA have been shown to be independently associated with worse prognosis in patients with HF-REF. The Sleep Heart Health Study identified OSA as an independent risk factor for the development of heart failure, with more impact in men than in women. Patients with CSA have been shown to have a reduced quality of life and to be at increased risk of developing cardiac arrhythmias. In addition, the prevalence of CSA–CSR appears to increase as the severity of heart failure increases and cardiac function decreases. Management of HF-REF starts with an accurate diagnosis and requires a rational combination of drug therapy and non-pharmacological management (education, fluid control, weight monitoring and physical exercise training). The use of beta-blockers or cardiac resynchronisation therapy results in a reduction of CSR. However, even in these patients with optimal