Purpose: This study aims to explore the factors linked to the occurrence of acute pulmonary thromboembolism (PE) within a cohort of patients exhibiting hypoxic saturation (oxygen saturation levels falling below 93%), subsequent to undergoing off-pump coronary artery bypass grafting (OPCABG).
Methods: A retrospective case-control study was conducted. A total of 296 patients met the inclusion and exclusion criteria, divided into PE group (100 cases) and non-PE group (196 cases) according to whether they had PE or not. The preoperative and postoperative information of patients were collected and statistically analyzed.
Results: The results from a multivariate logistic regression analysis indicated the following factors were independently linked to PE following OPCABG: history of smoking (OR = 3.019, 95% CI, 1.437– 6.634, P = 0.004), preoperative arterial oxygen partial pressure ≤ 78.9 mmHg (OR =  3.686, 95% CI, 1.708– 8.220, P = 0.001), presence of postoperative lower extremity deep venous thrombosis (OR = 4.125, 95% CI, 1.886– 9.310, P < 0.001), elevated postoperative D-dimer levels > 6.76 mg/l (OR = 8.078, 95% CI, 3.749– 18.217, P< 0.001), postoperative NT-BNP levels (OR = 1.001, 95% CI: 1.000– 1.001, P = 0.011), and elevated postoperative pulmonary arterial pressure > 33.0 mmHg (OR = 10.743, 95% CI: 3.422– 37.203, P < 0.001). The developed nomogram exhibited a high predictive accuracy with an area under the curve of 0.913 (95% CI: 0.878– 0.948).
Conclusion: When patients have a history of preoperative smoking, decreased preoperative arterial oxygen pressure, postoperative lower limb DVT, increased postoperative pulmonary artery pressure, and elevated postoperative D-Dimer and NT pro-BNP levels, it is recommended to take perioperative preventive measures, timely diagnostic evaluation, and if necessary, anticoagulant treatment. In addition, the results of this study may improve the diagnostic sensitivity of medical staff for postoperative PE in OPCABG, thereby increasing the detection rate and potentially reducing the need for excessive medical imaging procedures.

Keywords: case-control study, off-pump coronary artery bypass grafting, prediction model, pulmonary embolism, risk factor