New Insights into how Sleep Apnoea adversely affects Procedures to Cure Atrial Fibrillation

Obstructive sleep apnoea (OSA) is common in patients with atrial fibrillation (AF) and has been shown to be a risk factor for AF in a number of studies of patients with and without structural heart disease.

A series of studies have shown that OSA is associated with an increased risk of failure of treatment of AF by electrical cardioversion and attempts to cure AF by pulmonary vein isolation or PVI.

Pulmonary vein isolation is a complex procedure performed by Cardiac Electrophysiologists in which either radiofrequency energy (radiofrequency ablation) or intense cold (cryoablation) are used to create a barrier to the natural flow of electrical activity in the left atrium in the region where the veins returning blood from the lungs to the heart (pulmonary veins) enter it.

A recent landmark Australian study may explain the mechanism by which OSA causes PVI to fail more often. In this NHMRC funded study, published by Dr Hany Dimitri and colleagues in the prestigious journal,  Heart Rhythm (http://www.ncbi.nlm.nih.gov/pubmed/22016075), patients admitted for PVI had both overnight sleep studies and detailed studies of the structure and electrical properties of the atria (electro-anatomical mapping) before PVI was performed.

Although patients with and without OSA were similar in age, weight and blood pressure, OSA  patients had significantly larger atrial volumes with extensive areas of reduced, or absent, electrical activity. This may help to explain why PVI is less likely to restore and maintain normal rhythm in those AF patients who have significant OSA.

The study findings suggest that testing and treating OSA may well play an important role when patients with high burden AF are being considered for PVI.