Sleep apnea-CV link bolstered
MedWire News: The occurrence of breathing disturbances during sleep can directly trigger cardiac arrhythmias in some individuals, study findings published in the Journal of the American College of Cardiology suggest.
Meanwhile, a separate study in the same issue found that nocturnal breathing disturbances are commonplace in patients with hypertrophic cardiomyopathy (HCM).
Both studies give “important new insights into the pathophysiology of obstructive sleep apnea (OSA) and cardiovascular disease and have the potential to provide new therapeutic options for patients with heart disease,” said Ian Wilcox (Prince Alfred Medical Centre, Newtown, New South Wales, Australia) and Christopher Semsarian (University of Sydney) in an accompanying editorial.
Numerous studies have linked sleep disordered breathing (SDB) - of which OSA is the most common type - with hypertension, cardiovascular disease, and mortality. Notably, both OSA and HCM are independently associated with an increased risk for sudden cardiac death.
In the first of two studies investigating this relationship, Susan Redline (Case Western Reserve University, Cleveland, Ohio) and colleagues screened 2816 patients with a history of SDB. They took overnight polysomnograms to record episodes of apnea/ hypopnea and atrial fibrillation.
The team found that the rate of arrhythmias during sleep was low, occurring just 62 times in 57 participants. However, risk for nocturnal arrhythmia increased nearly 18 fold when immediately preceded by a respiratory disturbance relative to normal breathing pattern (odds ratio=17.5).
Redline et al said their findings confirm a “direct temporal relationship” between SDB events and the development of arrhythmias.
In the second study Jamil Tajik (Mayo Clinic Arizona, Scottsdale, USA) and colleagues used nocturnal oximetry to screen for respiratory disturbances in 100 patients diagnosed with HCM and 100 control participants with a similar age and gender distribution.
In all, 71 HCM patients had abnormal nocturnal oximetry (presence of episodes of transient desaturation followed by a rapid return to the baseline oxygen saturation level) – a significantly greater proportion than the 49% of control patients. Patients with abnormal oximetry were older and more commonly had hypertension than those with normal oximetry.
Tajik et al speculate that respiratory disturbances could, through increased sympathetic nervous activity, lead to an exacerbation of HCM symptoms.
In their editorial Wilcox and Semsarian say incorporating these findings in to clinical practice “will be critically dependent on cardiologists being more closely involved in the diagnosis and, potentially, treatment of OSA.”
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By Andrew Czyzewski