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Canadian Journal of Cardiology

Reply to Chen et al.—Obstructive Sleep Apnea Is a Risk Factor for Post Coronary Artery Bypass Graft Atrial Fibrillation

Published:November 21, 2014DOI:https://doi.org/10.1016/j.cjca.2014.11.016
      To the Editor:
      We thank Chen et al. for their detailed reading of our review.
      • Qaddoura A.
      • Kabali C.
      • Drew D.
      • et al.
      Obstructive sleep apnea as a predictor of post coronary artery bypass graft atrial fibrillation: a systematic review and meta-analysis.
      • Chen A.
      • Chen Y.
      Obstructive sleep apnea as a predictor of atrial fibrillation after coronary artery bypass grafting.
      We appreciate the opportunity to address their comments.
      The first comment concerns whether it was appropriate to include the study by Sharma et al.
      • Sharma S.
      • Daggubatti R.
      • Tribble R.W.
      • Petit S.J.
      • Gross K.
      Prevalence of obstructive sleep apnea in patients undergoing coronary artery bypass graft surgery (CABG). A pilot study.
      in our review given that we defined post–coronary artery bypass graft atrial fibrillation (PCAF) as an episode of AF from the end of the operation to hospital discharge. This is consistent with their study because they define new-onset AF as a postoperative complication during the hospital stay.
      • Sharma S.
      • Daggubatti R.
      • Tribble R.W.
      • Petit S.J.
      • Gross K.
      Prevalence of obstructive sleep apnea in patients undergoing coronary artery bypass graft surgery (CABG). A pilot study.
      Some end points were followed for 30 days, but this did not include PCAF.
      • Sharma S.
      • Daggubatti R.
      • Tribble R.W.
      • Petit S.J.
      • Gross K.
      Prevalence of obstructive sleep apnea in patients undergoing coronary artery bypass graft surgery (CABG). A pilot study.
      Although the article by Sharma et al.
      • Sharma S.
      • Daggubatti R.
      • Tribble R.W.
      • Petit S.J.
      • Gross K.
      Prevalence of obstructive sleep apnea in patients undergoing coronary artery bypass graft surgery (CABG). A pilot study.
      was eligible for our review, we conducted a subgroup analysis by excluding it for different reasons (Fig. 1). This analysis was deemed of lesser importance, and we omitted it from our review to provide readers with a more concise message. Comparing Figure 1 in this letter to Figure 2 of our review,
      • Qaddoura A.
      • Kabali C.
      • Drew D.
      • et al.
      Obstructive sleep apnea as a predictor of post coronary artery bypass graft atrial fibrillation: a systematic review and meta-analysis.
      removing Sharma et al.
      • Sharma S.
      • Daggubatti R.
      • Tribble R.W.
      • Petit S.J.
      • Gross K.
      Prevalence of obstructive sleep apnea in patients undergoing coronary artery bypass graft surgery (CABG). A pilot study.
      resulted in obstructive sleep apnea (OSA) being a stronger predictor of PCAF (odds ratio [OR], 2.21; 95% confidence interval [CI], 1.59-3.06] vs OR, 1.86; 95% CI, 1.24-2.80). In addition, removing this study substantially reduced detected heterogeneity (I2 < 0.01% vs I2 = 35%).
      Figure thumbnail gr1
      Figure 1Association between obstructive sleep apnea (OSA) and post–coronary artery bypass graft atrial fibrillation without the study by Sharma et al.
      • Sharma S.
      • Daggubatti R.
      • Tribble R.W.
      • Petit S.J.
      • Gross K.
      Prevalence of obstructive sleep apnea in patients undergoing coronary artery bypass graft surgery (CABG). A pilot study.
      CI, confidence interval; OR, odds ratio.
      Regarding the second comment, our review did not fully describe the subgroup analysis in Figure 3B.
      • Qaddoura A.
      • Kabali C.
      • Drew D.
      • et al.
      Obstructive sleep apnea as a predictor of post coronary artery bypass graft atrial fibrillation: a systematic review and meta-analysis.
      We appreciate the opportunity to clarify. We combined the data of severe OSA reported by Grilli et al.
      • Grilli F.
      • Pasquino S.
      • Gallinella E.
      • et al.
      Obstructive sleep apnea (OSA) and cardiovascular risk in patients undergoing CABG (coronary artery by-pass grafting).
      with all data evaluating OSA by polysomnography to assess the sensitivity of the pooled analysis to variations in OSA severity across studies. Figure 3B showed an increased risk of PCAF compared with Figure 3A, suggesting that severe OSA may influence the association.
      • Qaddoura A.
      • Kabali C.
      • Drew D.
      • et al.
      Obstructive sleep apnea as a predictor of post coronary artery bypass graft atrial fibrillation: a systematic review and meta-analysis.
      Evidently, this analysis is not sufficient to conclude that the risk of PCAF increases with OSA severity, and we acknowledged this as a limitation in our review. Our results provide an impetus for future studies to investigate this important question.
      Regarding the comment about the cutoff value for severe OSA, > 30 on the apnea-hypopnea index is the standard for severe OSA in the literature. This is consistent with Grilli et al., the only study that stratified their results by OSA severity in our review.
      • Grilli F.
      • Pasquino S.
      • Gallinella E.
      • et al.
      Obstructive sleep apnea (OSA) and cardiovascular risk in patients undergoing CABG (coronary artery by-pass grafting).
      We agree with Chen et al.
      • Chen A.
      • Chen Y.
      Obstructive sleep apnea as a predictor of atrial fibrillation after coronary artery bypass grafting.
      that larger high-quality studies may help confirm the findings of our review, but the evidence to date indicates that OSA is a risk factor for PCAF.

      Disclosures

      The authors have no conflicts of interest to disclose.

      References

        • Qaddoura A.
        • Kabali C.
        • Drew D.
        • et al.
        Obstructive sleep apnea as a predictor of post coronary artery bypass graft atrial fibrillation: a systematic review and meta-analysis.
        Can J Cardiol. 2014; 30: 1516-1522
        • Chen A.
        • Chen Y.
        Obstructive sleep apnea as a predictor of atrial fibrillation after coronary artery bypass grafting.
        Can J Cardiol. 2015; 31: 955.e1
        • Sharma S.
        • Daggubatti R.
        • Tribble R.W.
        • Petit S.J.
        • Gross K.
        Prevalence of obstructive sleep apnea in patients undergoing coronary artery bypass graft surgery (CABG). A pilot study.
        J Sleep Disord Treat Care. 2012; 1: 1-5
        • Grilli F.
        • Pasquino S.
        • Gallinella E.
        • et al.
        Obstructive sleep apnea (OSA) and cardiovascular risk in patients undergoing CABG (coronary artery by-pass grafting).
        Riv Ital Neurobiol. 2007; 4: 197-202

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