In Response.

Abstract

Listen

Translate article

We thank Drs Kaw and Mehra1 for their interest in our recent investigation that reported an increased risk for new-onset postoperative atrial fibrillation in patients with a high-probability for obstructive sleep apnea (OSA), assessed by the snoring, tired during the day, observed stop breathing during sleep, high blood pressure, body mass index more than 35 kg/m2, age more than 50 years, neck circumference more than 40 cm, and male gender (STOP-BANG) questionnaire. Drs Kaw and Mehra1 noted that our investigation used the STOP-BANG questionnaire, a well-validated screening tool, to identify patients at high risk for OSA, rather than polysomnography.2 STOP-BANG was an ideal instrument for our investigation, the purpose of which was to determine whether a brief and simple questionnaire administered during the preoperative assessment could identify elective cardiac surgical patients at elevated risk for postoperative atrial fibrillation. Of course, polysomnography provides more granular data to better characterize the patient’s sleep-disordered breathing, and is an excellent diagnostic tool for OSA. However, polysomnography data are available in only a few patients who present for cardiac surgery. The use of polysomnogram data would thus drastically reduce the sample size and prohibit an extensive analysis with adjustment for multiple confounding variables. Furthermore, the performance of polysomnography is complicated, time consuming, and certainly not possible during an outpatient preoperative assessment appointment. Our investigation did not adjust for age or obesity (or other risk factors included in STOP-BANG, such as gender or history of hypertension) because these variables are essential components of the STOP-BANG questionnaire. Adjustment for these variables would not allow us to test our hypothesis that STOP-BANG could predict risk of postoperative atrial fibrillation after cardiac surgery. However, our analysis adjusted for increased left atrial size, a potential mediator for the increased risk of atrial fibrillation associated with obesity.3 Although Kaw and Mehra1 mentioned that screening tools may underestimate risk for OSA in patients with cardiac disease, our results demonstrate that a higher score on this questionnaire successfully predicted increased risk for postoperative atrial fibrillation in our investigation. Our investigation included a sensitivity analysis in which STOP-BANG data were dichotomized into a low-risk group, with scores between 1 and 4, versus a high-risk group, with scores between 5 and 8, which examined the risk of atrial fibrillation in patients who had a high probability of moderate to severe OSA.4 We agree that frequent perioperative arterial blood gas and invasive hemodynamic monitoring after cardiac surgery allow more frequent detection of hypoxia and may possibly reduce the incidence of postoperative atrial fibrillation, although the lack of similarly aggressive monitoring likely has little effect in noncardiac surgery patients because the risk of new-onset postoperative atrial fibrillation is considerably lower.5 We agree that further investigation of the effect of objectively diagnosed OSA on important clinical outcomes after cardiac surgery and subsequent focus on interventions targeted to reverse OSA pathophysiology are needed. Marta Kelava, MDDepartment of Cardiothoracic AnesthesiaAnesthesiology InstituteCleveland ClinicCleveland, Ohio Andra E. Duncan, MD, MS, FASEDepartment of Cardiothoracic Anesthesia and Outcomes ResearchAnesthesiology InstituteCleveland ClinicCleveland, Ohio[email protected]