C-reactive protein as a predictor for developing post-operative atrial fibrillation: Author’s reply

We are grateful for the letter written by Xie et al.,1 which compares our study2 with other similar studies in the literature to help examine and support our findings. Their second reference involves a recent study by Tanaka et al.3 which found that increased high-sensitivity C-reactive Protein (hs-CRP) levels were associated with the development of atrial fibrillation (AF). Our study specifically investigated post-operative atrial fibrillation (POAF) after coronary artery bypass graft surgery, based on the hypothesis that the inflammation caused by the post-operative inflammatory response is a major aetiological factor in POAF development. Although the study by Tanaka et al.3 did not investigate AF in a surgical or post-operative setting, their findings do seem to support an important association between inflammation and AF development. Xie et al.1 suggest that pre- and post-operative CRP measurements may be helpful in terms of predicting POAF. We agree with this suggestion, which also seems to be getting an increasing amount of support in the literature. Regarding the usefulness of prospective structural myocardial changes and inflammatory markers in terms of predicting POAF, besides what is mentioned by Xie et al.,1 we also believe that the intraoperative damage caused by the cardiac surgical procedure, as well as the post-operative inflammatory response, are vital in the development of POAF. Speculatively, it might be possible that a relationship between structural myocardial changes and inflammatory markers may first be significant post-operatively. A study by Harada et al.4 include findings which indicate a relationship between inflammation (examined through the use of inflammatory markers) and atrial fibrosis—an important part of the pathophysiology of atrial fibrillation. In their letter, Xie et al.1 also mention a study which found an increased amount of certain immune cells in tissue from the left atrium in patients with AF. Thus, based on the literature, it seems likely that inflammation and structural myocardial changes are closely connected, though which one comes first is a matter of further discussion. As stated by Xie et al.,1 more studies are needed to examine the usefulness of CRP and other inflammatory markers in the prediction of POAF (rather than only investigating the association between CRP and POAF/AF). It is important for future studies to be aware of the many factors that may influence CRP such as comorbidities, age, and infections. These future studies may reveal biomarkers with the potential to assist with the prediction of POAF/AF, which may aid in the identification of high-risk patients prior to or just after cardiac surgery. Speculatively this may facilitate the use of therapies to prevent the development of POAF or perhaps AF in general, which may help to lower the overall morbidity and mortality associated with these conditions. Conflict of interest: O.J.O.: none declared; E.L.F.: Independent research grant from Janssen Pharmaceutical and BMS.