Author + information
- Thomas Nyström, MD, PhD,
- Martin J. Holzmann, MD, PhD and
- Ulrik Sartipy, MD, PhD∗ ()
- ↵∗Department of Cardiothoracic Surgery and Anesthesiology, Karolinska University Hospital, Stockholm SE-171 76, Sweden
We thank Dr. Xue and colleagues for their interest and comments regarding our paper (1). Dr. Xue and colleagues were concerned that the lack of information regarding pre- and post-operative hemoglobin levels and perioperative transfusions in our study would have biased the results. We did not have this information, and we agree that information regarding pre-operative hemoglobin levels would have been interesting because hemoglobin level has been shown to be associated with HbA1c in patients with type 2 diabetes (2). However, because the association between hemoglobin level and HbA1c in previous studies was very weak (2), we find it unlikely that the lack of information regarding preoperative hemoglobin levels influenced our main findings that poor glycemic control was associated with increased long-term risk of death or a major adverse cardiovascular event.
Dr. Xue and colleagues also expressed concern regarding the variables included in the multivariable models used to estimate adjusted hazard ratios for the association between HbA1c categories and a combination of death or a major adverse cardiovascular event. They argued that we should have included post-operative complications in the multivariable models. We disagree because control for intermediates (i.e., factors that are on the causal pathway between the exposure and the outcome, such as post-operative complications) will generally bias estimates of the effect toward no effect (3).
Last, Dr. Xue and colleagues stated that it has been shown that “established preoperative risk factors are not good predictors of adverse outcomes and long-term survival after CABG.” We wish to emphasize that well-known cardiac surgery risk prediction models, although developed for assessment of operative risk, have been demonstrated to perform well for the prediction of long-term survival (4,5).
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2015 American College of Cardiology Foundation