Obstructive sleep apnoea syndrome (OSAS) causes nocturnal chronic intermittent hypoxia (IH) that contributes to excess cardiovascular morbidity. To explore the consequences of IH, we used our recently developed model of nocturnal IH in healthy humans to characterise the profile of this blood pressure increase, to determine if it is sustained and to explore potential physiological mechanisms.We performed 24-h ambulatory monitoring of blood pressure in 12 healthy subjects before and after 2 weeks of IH exposure. We also assessed systemic haemodynamics, muscle sympathetic nerve activity (MSNA), ischaemic calf blood flow responses and baroreflex gain. We obtained blood samples for inflammatory markers before, during and after exposure. IH significantly increased daytime ambulatory blood pressure after a single night of exposure (3 mmHg for mean and diastolic) and further increased daytime pressures after 2 weeks of exposure (8 mmHg systolic and 5 mmHg diastolic). Mean¡SD MSNA increased across the exposure (17.2¡5.1 versus 21.7¡7.3 bursts?min -1 ; p,0.01) and baroreflex control of sympathetic outflow declined from -965.3¡375.1 to -598.4¡162.6 AIU?min -1 ?mmHg -1 (p,0.01). There were no evident changes in either vascular reactivity or systemic inflammatory markers. These data are the first to show that the arterial pressure rise is sustained throughout the waking hours beyond the acute phase immediately after exposure. Moreover, they may suggest that sympathoactivation induced by IH likely contributes to blood pressure elevation and may derive from reduced baroreflex inhibition. These mechanisms may reflect those underlying the blood pressure elevation associated with OSAS.

Obstructive sleep apnea (OSA) is associated with cardiovascular morbidity and mortality, largely as a result of myocardial anomalies. Numerous mechanisms cause OSA-related myocardial damage. The majority are initiated as a result of OSA-induced, chronic, intermittent hypoxia. The most-important mechanisms that lead to myocardial damage are increased sympathetic activity, endothelial dysfunction, systemic inflammation, oxidative stress, and metabolic anomalies. All these mechanisms promote the development of hypertension, which is common in patients with OSA. Hypertensive cardiomyopathy and coronary heart disease, as well as obesity-related, diabetic, and tachycardia-induced cardiomyopathies, are also associated with OSA. Left ventricular hypertrophy, myocardial fibrosis, atrial dilatation, and left ventricular systolic and diastolic dysfunction in patients with OSA explain the association of the disease with these clinical outcomes. The gold-standard treatment for OSA, nasal continuous positive airway pressure (CPAP), might improve cardiac symptoms and hemodynamic parameters in patients with the disease. However, large clinical trials are required to improve our understanding of the cardiac consequences of OSA, and determine the effect of treatment, particularly CPAP, on myocardial damage in symptomatic patients and primary prevention of cardiovascular disorders.

No abstract

Fibromuscular dysplasia (FMD) commonly affects the renal and cervical arteries but has been described to affect other vascular beds as well. The prevalence of and clinical characteristics associated with multisite FMD (string-of-beds or focal stenoses affecting at least 2 vascular beds) are not known. In the prospective ARCADIA registry (Assessment of Renal and Cervical Artery Dysplasia), symptomatic patients with renal artery (RA) FMD underwent tomographic- or magnetic resonance-angiography from the aortic arch to the intracranial arteries and those with cervical FMD from the diaphragm to the pelvis. Of 469 patients (84.0% women), 225 (48.0%) had multisite FMD. In addition, 86 of 244 patients with single-site disease had dissections or aneurisms affecting other vascular beds, totaling 311 patients (66.3%) with lesions in >1 vascular bed. Among patients with a cerebrovascular presentation, the prevalence of RA lesions was higher in patients with than in those without hypertension (odds ratio, 3.4; 95% confidence interval, 1.99–6.15). Among patients with a renal presentation, the prevalence of cervical lesions was higher in patients with bilateral than in those with unilateral RA lesions (odds ratio, 1.9; 95% confidence interval, 0.99–3.57). In conclusion, FMD is a systemic arterial disease. At least 2 vascular beds were affected by dysplastic stenoses in 48.0% of cases and by dysplastic stenoses, aneurysms, and dissections in 66.1% of cases. RA imaging should be proposed to hypertensive patients with a cerebrovascular presentation. Cervical artery imaging should be considered in patients with a renal presentation and bilateral RA lesions. Clinical Trial Registration— URL: www.Clinicaltrials.gov . Unique identifier: NCT02884141.