he STOP-Bang questionnaire is an eight-item questionnaire that asks about snoring, tiredness, observed apneas, blood pressure, BMI (more the 35), age (more than 50), neck circumference (more than 16 inches or 40 cm), and gender (male). role in OSA-related hypertension. In fact, since hyperaldosteronism and OSA have been shown to occur together, patients with resistant hypertension being evaluated for one condition may benefit from an evaluation of the other condition. Finally, reduced slow wave sleep, which is associated with OSA, may result in impaired vascular function and increased sympathetic activity. Treatment of OSA with continuous positive airway pressure (CPAP) has been shown to result in a reduction is systemic BP. Although the overall impact of CPAP on BP reduction is small, a larger impact is seen in those with more severe OSA, difficult-to-control hypertension, and better CPAP compliance. Taken together, the above evidence suggests a need for more screening for OSA in the population of patients with resistant hypertension. Coronary Heart Disease The prevalence of OSA in people with CHD is approximately 30-60 percent Amongst men hospitalized for an acute myocardial infarction (MI), the prevalence is as high as 70 percent In the Sleep Heart Health
Study (SHHS), where more than 6,000 people were followed for over eight years, the risk of CHD-related death in men was 70 percent higher in those with an AHI of 15 or more compared to those without OSA. Other studies have shown that MI may be associated with worsening of sleep-disordered breathing. These data are not surprising given the association of OSA
The presence of Coronary Heart Disease, particularly in men, should warn clinicians that screening for OSA may be indicated.
with a number of cardiovascular risk factors including decreased high density lipoprotein (HDL) and increased C-reactive protein (CRP), homocysteine, and blood glucose. Recurrent hypoxemia causes the release of vasoactive substances, such as endothelin, that may result in vasoconstriction that persists for hours. Interestingly, endothelin levels fall after four hours of CPAP therapy.
8 SAN MATEO COUNTY PHYSICIAN | JANUARY 2014
The presence of CHD, particularly in men, should warn clinicians that screening for OSA may be indicated. This is particularly important since patients with OSA who are treated with CPAP have a lower incidence of fatal and non-fatal cardiovascular events compared to those with untreated severe OSA. Cardiac Arrhythmias Multiple studies have demonstrated that atrial fibrillation (AF) and nonsustained ventricular tachycardia (NSVT) are more prevalent in individuals with OSA than in those who are unaffected. Conversely, amongst patients with AF, the prevalence of OSA is high (estimates range from 32 to 82 percent). In one study, a paroxysm of AF or an episode of NSVT was 18 times more likely within 90 seconds of an apneic or hypopneic event compared to normal breathing. Another study showed that the diagnosis of OSA increased the risk of recurrent AF after radiofrequency catheter ablation by about 25 percent. Patients who have untreated OSA and AF and are cardioverted into sinus rhythm are twice as likely to have recurrent AF compared to those with treated OSA. Additionally, due to activation of the cardiac vagal system, OSA is also associated with bradycardia and asystole during sleep as well as bradyarrhythmias during waking hours. In one study, the prevalence of OSA amongst patients with pacemakers was almost 60 percent. This raises the question of whether some patients being referred for pacemaker implantation would benefit from first being screened and treated for OSA.