The present study found that the new-onset AF after OPCAB was concentrated within the first 4 days after surgery, which is consistent with previous studies . The incidence of AF in our study was 28.75% within the incidence of prior studies . Age is one of the most consistent risk factors for postoperative AF in many previous literature , which was also supported by our research. The effect of advanced age on AF may relate to degenerative changes in atrial structure and function .
Studies have found that patients with peripheral vascular disease had a high probability of being accompanied by atherosclerosis of other blood vessels , and the risk of cardiovascular events increases with the severity of peripheral vascular disease  . Our study found that peripheral vascular disease was an independent risk factor for new-onset AF after OPCAB, which is consistent with the conclusions of Pollock et al. Their study included 9416 patients with isolated CABG in multiple centers, and found that patients with peripheral vascular disease were more likely to develop new-onset postoperative AF .
OPCAB mainly includes two types of procedures: cOPCAB and MID-OPCAB. To our best knowledge, there are currently no studies especially focus on the relationship between the two types of OPCAB and postoperative new-onset AF. In this study, the binary logistic regression analysis showed that patients underwent cOPCAB had a significant more risk of postoperative AF than patients had MID-OPCAB. Nevertheless, it is also noteworthy that patients undergoing MID-OPCAB were younger, had better cardiac function and fewer coronary vessel lesions.
Most previous studies involved just one of ICU time and mechanical ventilation time, and rarely combined analysis of the two . Different from other studies, we included two variables mentioned above and found that only mechanical ventilation time was an independent risk factor of AF after OPCAB. Supporting our results, Filardo et al. had the same result from their study , and they reported that both ICU time and mechanical ventilation time were statistically associated with postoperative AF in the univariate analysis, but mechanical ventilation time is the only one correlated significantly with AF after analyzed by logistic analysis.
In the present study, the proportion of patients with AF using IABP was significantly higher than that of non-AF. IABP is not a variable often included in previous research. Consistent with our findings, Lewicki et al. conducted a study included 1836 patients who underwent CABG and identified that IABP was an independent predictor of new-onset AF after CABG . Inversely, Thoren et al. disagreed with this conclusion .It might be due to the fact that the majority of the operations (96%) were performed on-pump in their study cohort, which is dramatically different from ours.
New-onset AF was clearly associated with more in-hospital complications. Similar to previous studies, we found patients with postoperative AF had higher risk of reoperation, re-intubation, postoperative myocardial infarction, stroke, renal failure, and in-hospital death     . However, we could not show any association between postoperative stroke and AF, which was supported by previous studies   . This might result from the fact that our study excluded patients who underwent concomitant valve surgery and only concentrated on in-hospital complications. To our best knowledge, previous studies of AF after CABG did not include re-entry into ICU and re-ICU time. From our study, we, firstly, demonstrated that the two variables above are all statistically significant between the two groups.
This is a retrospective single center observational study. One of the major limitations is intrinsic to the observational nature of this study, which cannot adjust for unobserved or unknown confounders. Furthermore, the Chinese patient population might limit the generalizability of these reported findings. Finally, given the AF definition that the abnormal atrial originated rhythm be documented for at least 30 s, it is possible that the overall rate for AF occurrences may have been underreported.