Abstract: Objective To analyze the relationship between left ventricular four-dimensional myocardial strain and cardiac function improvement after coronary artery bypass grafting (CABG) in patients with coronary heart disease(CHD) and its predictive value. 
Methods A total of 120 patients with CHD who underwent elective CABG at Bishan Hospital Affiliated to Chongqing Medical University were selected. The improvement of cardiac function at 6 months after surgery was statistically analyzed, and the patients were divided into the improvement group (with improved cardiac function) and the non-improvement group (without improvement in cardiac function). The preoperative left ventricular function indicators ［left ventricular ejection fraction (LVEF), left atrial area (LAA), left ventricular end-diastolic diameter (LVEDD), left ventricular mass index (LVMI)］ and left ventricular four-dimensional myocardial strain parameters ［global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), global area strain (GAS)］ were compared between the two groups. The correlation between preoperative left ventricular four-dimensional myocardial strain parameters and postoperative cardiac function improvement in patients with CHD undergoing CABG was analyzed, and the value of preoperative left ventricular four-dimensional myocardial strain parameters in predicting postoperative cardiac function improvement in patients with CHD undergoing CABG was also analyzed. 
Results In patients with CHD who underwent CABG, 84 patients showed improvement in cardiac function at 6 months after surgery, with an improvement rate of 70.00%. The preoperative LVEF and GRS were lower in the non-improvement group than in the improvement group, while LVEDD, LVMI, GLS, GCS, and GAS were higher in the non-improvement group than in the improvement group (P＜0.05). Preoperative GLS (OR=1.330, 95%CI: 1.123-1.576), GCS (OR=1.195, 95%CI: 1.075-1.328), GRS (OR=0.879, 95%CI: 0.815-0.947), and GAS (OR=1.221, 95%CI: 1.102-1.352) were significantly associated with postoperative cardiac function improvement (P＜ 0.05). The area under the curve (AUC) values of preoperative GLS, GCS, GRS, GAS, LVEF, LVEDD, and LVMI for predicting postoperative cardiac function improvement were 0.761 (95%CI: 0.675-0.834), 0.757 (95%CI: 0.671-0.831), 0.758 (95%CI: 0.671-0.831), 0.755 (95%CI: 0.668-0.829), 0.759 (95%CI: 0.673-0.833), 0.757 (95%CI: 0.670-0.831), and 0.751 (95%CI: 0.664-0.826), respectively. No significant differences were observed in the AUC values of preoperative GLS, GCS, GRS, and GAS, as well as LVEF, LVEDD, and LVMI for predicting postoperative cardiac function improvement (P＞0.05). The AUC for predicting postoperative cardiac function improvement in patients with CHD after CABG, using a combination of preoperative GLS, GCS, GRS, and GAS, was 0.896 (95%CI: 0.828-0.945), which was higher than that predicted by preoperative GLS, GCS, GRS, and GAS alone (P＜0.05). 
Conclusion Left ventricular four-dimensional myocardial strain parameters before CABG are significantly correlated with postoperative cardiac function improvement in patients with CHD, and can help predict the improvement of cardiac function. 

Key words: coronary heart disease, coronary artery bypass grafting, four-dimensional myocardial strain