A Propensity Score Matching Clinical Analysis On The Mortality Risk Factors Associated With Early Postoperative Mortality After Valve Surgery

Background and ObjectiveIn recent years,the number of patients undergoing valve replacement surgery had increased,with the complication and mortality after cardiac valve replacement decreased gradually.However,there are still some patients with severe complications after surgery,even leading to death in the hospital.Further study of the factors associated with mortality after valvular heart surgery may help to improve the prognosis of valvular heart surgery.In this article,the early death cases after cardiac valve surgery were analysed retrospectively in our department in recent years and the risk factors associated with early postoperative mortality for the patients underwent valve surgery would be discussed by using propensity score matching.Methods1.A total of 4128 patients were underwent valve surgery in the Second Affiliated Hospital of Army Military Medical University from September 2016 to August 2019.patients who died after cardiac valve surgery were included in the death group（three patients were excluded because of incomplete medical records）.patients discharged from hospital after cardiac valve surgery were randomly selected to be included in the control group.PSM was used to screen the two groups of patients.The clinical characteristics,including intraoperative blood loss,intraoperative heparin dosage,the lowest temperature during cardiopulmonary bypass（CPB）,the type of Cardioplegia,the use of intra-aortic balloon pump（IABP）,the surgery procedures（including ablation,coronary bypass surgery,tricuspid valve surgery）,the type of artificial valve,post operative blood gas analysis were compared between two groups.The risk factors associated with early postoperative mortality for the patients underwent valve surgery were analyzed,and ROC curves were drawn.The predictive value of risk factors associated with early postoperative mortality after valvular heart surgery was calculated.2.A total of 46 dead patients selected by PSM were included in the death group and 46cured patients were included in the control group.The values of pH,Pa CO_2,Pa O₂and plasma lactate were collected in the perioperative period in two groups.Including 30min before operation,intraoperative,and 0 to 48 hours after ICU admission（recorded every 6 hours）.The changes of pH value,Pa CO_2,Pa O₂and plasma lactate in the two groups were plotted from pre-operation to 48 hours after admission to intensive care unit.Results1.Risk factors associated with early postoperative mortality after valve surgery（1）Ninety-two patients were selected by propensity score,including 46 in the death group and 46 in the control group.The main causes of death after cardiac valve replacement were low cardiac output syndrome（32%）,malignant arrhythmia（28%）,multiple organ failure（20%）.The patients in the death group owned more intraoperative blood loss,more IABP,higher postoperative Pa CO₂and level of lactate compared with control group（P<0.05）,while the postoperative Pa O₂,hematocrit value and Sa O₂were lower than control group（P<0.05）.（2）Higher Pa CO2（OR 1.090,95%CI:1.018-1.166,P<0.05）were associated with early postoperative mortality after valve surgery.The area under ROC curve of Pa CO₂were 0.793,the threshold of Pa CO₂were 49.5mm Hg.（3）Hyperlactatemia（OR 1.551,95%CI:1.270-1.894,P<0.05）were associated with early postoperative mortality after valve surgery.The area under ROC curve of lactate were0.918,the threshold of lactate were 7.55mmol/L.2.Variation trend of blood gas analysis index in the perioperative period（1）There was no statistical difference in pH value between the two groups in the perioperative period.Pa CO₂in the death group was lower than that in the control group 24hours After ICU admission（P<0.05）.Pa O₂in the death group was lower than that in the control group 42 hours After ICU admission（P<0.05）.Lactate in the death group was higher than that in the control group After 24 hours in ICU（P<0.05）.（2）pH values in the two groups was stable in the perioperative period.Pa CO₂showed a downward trend in the two groups after surgery,which began to increase at 6h after ICU admission.Pa O₂showed a downward trend in the two groups after surgery,which is stable at24h after ICU admission.Postoperative lactate in the two groups showed a gradual upward trend,and the plasma lactate in the control group decreased earlier than in the death group.Conclusion1.The main causes of death after cardiac valve replacement were low cardiac output syndrome,malignant arrhythmia,multiple organ failure.Among them,postoperative low cardiac output syndrome is the most common cause of death.2.By using propensity score matching analysis,clinical index including age,sex,body mass index,smoking history,cardiac function grade,history of cardiac surgery,preoperative complications（including diabetes mellitus,renal insufficiency,hypertension,atrial fibrillation,coronary stenosis）,preoperative left ventricular ejection fraction,CPB time,and multi-valve surgery were consistent between the two groups.It found that hypercapnia under autonomous respiration condition and hyperlactatemia were risk factors associated with early postoperative mortality after valve surgery.3.By analyzing the variation trend of blood gas analysis indexes during the perioperative period of cardiac valve surgery in the two groups,It found that patients in the death group had persistent hyperlactatemia after valve surgery.Hyperlactatemia indicates postoperative adverse outcomes,persistent hyperlactatemia might be a important predictor associated with early postoperative mortality after valve surgery.