Up to 15% of all strokes are caused by Atrial Fibrillation (AF) increasing the risk of stroke by 4.8% (hypertension are 3.4% and Coronary Artery Disease 2.4% respectively). It is the most common type of arrhythmia, affecting approximately 350,000 Canadians.
This risk increases with age, beyond age 60, one-third of all strokes are caused by AF. with, 3-5 times greater risk for ischemic stroke, and cryptogenic strokes accounting for 25% of the total.
A strong association exists between Obstructive Sleep Apnea (OSA) and AF; OSA is clearly more prevalent in patients with AF than even high-risk patients with multiple ‘other cardiovascular diseases’ yet OSA does not appear in the CHADS2 Risk Criteria (used as a determination of the risk associated with anticoagulant therapy for AFib) ?
Physicians are presently therefore often more likely to use anticoagulants which are known to carry a very high risk, rather than have the patient tested for OSA despite the known association.
With AF patients scheduled for electro-cardioversion, two 2009 studies showed a prevalence of OSA present at 42.7% and 81.6% respectively. This is significant.
OBSTRUCTIVE SLEEP APNEA AND ATRIAL FIBRILLATION.
OSA is more commonly observed in patients with AF and the incidence of AF is considerably higher in those with OSA. In the Sleep Heart Health Study (2006) patients with severe OSA had a 4-fold increased risk for atrial fibrillation.
There are proposed pathophysiologic mechanisms linking OSA to the development of AF. These include complex interactions of hemodynamic and sympathetic results of OSA (including autonomic dysregulation, elevated sympathetic tone, oxidative stresses, endothelial dysfunction, and left atrial stretch.
When the diaphragm drops to “suck” outside air in, in the case of an airway blockage the chest (intra-thoracic) pressure drops significantly putting strain on the heart and great vessels.
“Bearing down” when using the toilet can actually stimulate the vagus nerve. (Valsalva Maneuver)The vagus nerve can slow the heart rate considerably (the vagal response). The vagal response can even trigger cardiac arrest and death in an individual with an already existing heart condition. In Tony Soprano’s crime family, Gigi Cestone, died on the toilet, likely due to stress following the Valsalva maneuver.
This indicates the effect intrathoracic pressure may have on heart rate.
Given the prevalence of OSA among patients with AF and its impact on outcomes, clinicians are recommended to assess individuals with AF for sleep disordered breathing and specific treatment of snoring and OSA may be needed to reduce risk of recurrence. In the 2013 study by Neilan only half of patients diagnosed with OSA were adherent to CPAP, therefore other therapeutic modalities such as oral appliance therapy clearly have their place. Their conclusions;
Patients with SA have an increased blood pressure, pulmonary artery pressure, right ventricular volume, left atrial size, and left ventricular mass.
OSA therapy is associated with lower blood pressure, atrial size, and ventricular mass, and a lower risk of AF recurrence after treatment. Better still – prevention by screening for hypertension and OSA both are epidemic in our society.