09 Mar Cerebral haemodynamics is altered in patients with sleep apnoea/hypopnea syndrome
According to recent epidemiologic studies, patients with sleep apnoea/hypopnea syndrome (SAHS) are at increased risk of cardiovascular diseases, including stroke. Stroke is a serious and common disorder and a major cause of death worldwide. Nocturnal apnoeas can trigger acute cerebral ischemia in predisposed patients and impaired vasodilation is present in SAHA, however, few studies have explored vascular cerebral dysfunction and often gave inconclusive results. A recent study by R. Coloma Navarro and team has assessed whether patients with sleep apnoea have impaired haemodynamics when compared to contols, and to investigate a possible relationship with clinical data.
The research team studied one group of 76 patients with diagnosed sleep apnoea and a control group of 76 subjects matched for age, sex and main cardiovascular risk factors. Subjects whose apnoea/hypopnoea index (AHI), measured in overnight polysomnographic tests, was greater than 10/hr were included in the test group. Control subjects were excluded on the basis of chronic or heavy snoring, witnessed nocturnal apnoeas or excessive daytime sleepiness [Epworth Sleepiness Scale (ESS) ≥10].
Patients undertook 16-channel polysomnographic sleep studies with sleep stages and EEG arousal detection being scored according to current standard criteria. Furthermore, Transcranial Doppler was performed on all patients. All the subjects were studied in the morning, between 10 a.m. and 12 a.m., in a quiet, semi-dark room, resting in a supine position. SAHS patients were studied within a month of the sleep study. All the tests were performed by the same investigator, who was blind to the results of the sleep study. First, the participants were routinely examined with continuous color-coded duplex ultrasound. If a significant (>50 %) stenosis was found, the patient was excluded from the study. Second, intracranial arteries (middle cerebral arteries—MCA, anterior cerebral arteries—ACA, posterior cerebral arteries—PCA and basilar artery—BA) were identified through the temporal (MCA, ACA and PCA) or suboccipital (BA) windows by transcranial Doppler (TCD). The peak systolic velocity (PSV) and end diastolic velocity (EDV) were recorded for each artery. The mean blood flow velocity (MFV) was calculated.
The study found that daytime cerebral haemodynamics is abnormal in patients affected by sleep apnoea. Specifically, a reduction in mean blood flow velocity was seen compared to controls. Lower MFV has been related to cognitive impairment and to the severity of nocturnal hypoxia in SAHS.
This study highlights the impairment of daytime cerebral haemodynamics in patients with severe SAHS. These findings point out to possible functional and structural changes in cerebral microcirculation and perhaps in large intracranial arteries too as a potential mechanism to help to explain the increased risk of stroke in these patients.
Journal Reference:
Coloma Navarro, R. ; Jiménez Caballero, P. ; Vega, G. ; Ayo-Martín, O. ; Segura Martín, T., Cerebral hemodynamics is altered in patients with sleep apnea/hypopnea syndrome. SpringerPlus, 2016, Vol.5(1), pp.1-10 [Peer Reviewed Journal]