Sleep Apnea Linked to Post-Surgery Atrial Fibrillation

APRIL 16, 2015
Andrew Smith
 
Study results indicate that obstructive sleep apnea is an independent predictor of atrial fibrillation (AF) in cardiac surgery.
 
Researchers analyzed records from 545 patients who underwent coronary artery bypass grafting (CABG), aortic valve replacement, mitral valve replacement/repair, or combined valve/CABG surgery.
 
The patients, who were treated at a single university hospital between January 2008 and April 2011, had no history of AF, and they all exhibited normal sinus rhythm before their procedures began.
 
After their procedures, however, 226 of them (41%) developed AF.
 
When the researchers looked at the impact of obstructive sleep apnea, they found that 67% of the 72 patients with apnea, but only 38% of the 473 patients with no apnea, went on to develop postoperative AF (adjusted hazard ratio [HR], 1.83; 95% confidence interval [CI], 1.30-2.58, p < 0.001).
 
Further analysis showed that patients with obstructive sleep apnea might be able to reduce their chance of developing postoperative AF by using a positive airway pressure therapy system at home.
 
The observed rate of postoperative AF was 56% (18 of 32) for apnea patients who used positive pressure therapy at home and 76% (29 of 38) for apnea patients who did not use such systems.
 
Unfortunately, patient numbers were not high enough to demonstrate any conclusive effect (unadjusted HR, 0.63; 95% CI: 0.35 to 1.15; p = 0.13).
 
“Further investigation is needed to determine whether use of positive airway pressure in obstructive sleep apnea patients reduces the risk of postoperative AF,” the study authors wrote in the Journal of Cardiothoracic and Vascular Anesthesia.
 
The numbers underlying the main finding, however, were strong enough for the authors to state it with confidence, even after they noted the study’s retrospective nature and its relatively small patient count.
 
“Obstructive sleep apnea is significantly associated with postoperative AF in cardiac surgery patients,” they wrote.
 
Minimizing cases of postoperative AF is important, according to a recent study published in Circulation, because “isolated” cases of AF caused by temporary secondary precipitants such as surgery often become chronic long-term conditions.
 
Indeed, the 5-year, 10-year and 15-year recurrence rates for 439 patients whose initial AF stemmed from a temporary cause (and surgery was the most common temporary cause) were 42%, 56% and 62%.
 
Patients who developed isolated AF from causes like surgery, moreover, were as likely to suffer strokes and nearly as likely to suffer heart failure as those who started with paroxysmal cases of AF.
 
Prior research has identified several factors that increase the risk of postoperative AF.
 
Among the best documented — and easiest to measure — of those risk factors is a patient’s CHADS2 score, which considers 5 factors: Congestive heart failure, Hypertension, Age 75+, Diabetes mellitus, Stroke or TIA or thromboembolism. Patients receive 1 point for each of the first 4 risk factors and 2 points for a history of strokes, so scores range from 0 to 6.
 
A recent study by Mayo Clinic researchers analyzed records from 1,566 patients who underwent thoracic or vascular surgery and found that each 1-unit increase in a patient’s CHADS2 score was associated with a 22% greater risk of postoperative AF.
 
Previous research has also uncovered some strategies for reducing the risk that patients will develop AF after various types of surgery.
 
Patients taking beta-blockers, for example, should often continue taking them (though possibly at lower doses) on a normal schedule to avoid withdrawal. There is also some evidence that postoperative magnesium can reduce AF, at least in patients with low serum magnesium, and that preventative administration of medications such as diltiazem or amiodarone can protect some high-risk patients.
 

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