【研究背景】

急性A型主动脉夹层（ATAAD）是一种起病急骤、症状严重的高致死性心血管急症，以剧烈的撕裂样胸背痛为特征。尽管手术技术与围术期管理不断进步，ATAAD患者术后仍面临高死亡率及呼吸、神经、肾功能等多系统并发症风险，其中术后机械通气时间延长（PMV）常伴随肺炎、再插管、气管切开等问题，严重阻碍康复进程。目前关于ATAAD术后机械通气时间（MVT）与手术死亡率关系的研究较少，且缺乏统一定义与大规模数据支持。因此，基于大规模数据深入探讨两者关系，对优化围术期管理、降低手术风险、提升康复质量具有重要临床意义，可为临床决策及医疗资源分配提供科学依据，改善ATAAD患者整体预后。

【研究目的】

本研究旨在分析本中心ATAAD手术患者的术后MVT与手术死亡率的关系，明确不良预后患者MVT的特征，为精准定义术后PMV提供依据。同时，研究将识别PMV的高危因素并构建预测模型，助力医疗人员早期识别高风险患者并实施针对性呼吸康复策略，以改善ATAAD患者的术后恢复和预后。

【研究方法】

本回顾性研究纳入了2011至2019年于南京鼓楼医院接受ATAAD手术的1049名患者。首先按术后MVT将患者分为五个亚组（<12小时、12小时至<24小时、24小时至<48小时、48小时至<72小时、≥72小时），对比各组临床特征及预后，并通过多变量Logistic回归分析探讨MVT与手术死亡率及术后气管切开等不良事件的关联。

基于MVT高危区间定义术后PMV，对比PMV组与非PMV组患者的临床特征差异，识别ATAAD术后PMV的独立危险因素。利用列线图模型将危险因素评估结果可视化，旨在为临床提供直观的风险评估工具，优化围术期管理决策。

【研究结果】

第一部分：

1）本研究对2011年至2019年在南京鼓楼医院接受ATAAD手术的1049名患者进行了回顾性分析。研究结果显示，患者总体死亡率为11.82%（124 / 1049），平均年龄为53.02 ± 13.21岁，其中男性患者占比74.83%。通过MVT亚组分析，我们发现术后MVT较长的患者群体在术前存在更多合并症，例如脑缺血和心包积液。这些患者手术时间更长、术中输血量也更多。术后，这些患者更有可能经历气管切开、缺血性脑卒中、手术部位感染和再次手术探查等不良事件。

2）我们进一步将研究人群根据短期生存结局分为存活组（925名患者）和死亡组（124名患者）。通过比较两组患者的术前、术中和术后临床特征，我们发现死亡组患者平均年龄更高，术前合并心包积液和肢体缺血的比例升高。死亡组中，心肌缺血的表现更为常见，且这些患者在ATAAD手术中更可能接受同期手术内的冠状动脉搭桥（CABG）术。术中资料对比显示，死亡组患者的体外循环（CPB）和主动脉阻断（ACC）时间更长，术中输血量也更多。术后资料的比较也同样提示死亡组患者发生复杂并发症的可能性更高。

3）通过Logistic回归分析识别与ATAAD患者手术死亡率升高的显著危险因素，包括高龄、术前合并心包积液、术中同期行CABG手术、CPB时间≥ 208分钟、大量术中输血、术后脑出血、脑梗、胃肠道出血、手术部位感染以及MVT ≥ 72小时。

4）在本研究人群中，有5.00%（52 / 1049）的患者经历了气管切开。Logistic回归分析提示高龄、术后脑卒中和MVT ≥ 72小时是与术后气管切开风险升高密切相关的因素。

第二部分：

1）本研究中，26.98%的ATAAD患者在术后经历了72小时以上的机械通气（MVT ≥ 72小时），这些患者更有可能经历气管切开、脑卒中、截瘫、肢体缺血、手术部位感染以及再次手术探查等严重并发症。

2）为了深入理解这一现象，我们将MVT ≥ 72小时设定为PMV的时间节点，并运用回归模型分析其背后的独立危险因素。研究结果揭示，高龄、术前脑缺血、升主动脉置换手术、同期CABG手术、较长的CPB时间以及术中大量新鲜冰冻血浆的输入是PMV的独立危险因素。这些因素被纳入列线图模型中，该模型经过验证，展现出了优秀的预测能力，为临床提供了一个直观的工具，以预测ATAAD患者术后PMV的风险。

【研究结论】

本研究揭示，术后机械通气时间延长（PMV，即MVT≥72小时）是ATAAD术后常见且严重的并发症，将显著增加手术死亡率及再插管等不良事件风险。研究强调，促进患者在术后72小时内安全拔管对改善预后至关重要。基于大规模ATAAD患者数据开发的列线图模型可有效预测术后PMV的发生，为临床医生提供精准指导，优化治疗方案，降低PMV风险，从而改善患者术后恢复和生存质量。

Background

Acute Type A Aortic Dissection (ATAAD) is a highly lethal cardiovascular emergency characterized by sudden onset and severe symptoms, typically presenting with intense, tearing chest and back pain. Despite advancements in surgical techniques and perioperative management, patients with ATAAD still face high mortality rates and the risk of complications involving multiple systems, including respiratory, neurological, and renal functions. Postoperative prolonged mechanical ventilation (PMV) is a common issue in these patients, often accompanied by pneumonia, reintubation, and tracheostomy, which significantly hinder the recovery process. Currently, there is a paucity of research on the relationship between postoperative mechanical ventilation time (MVT) and surgical mortality in ATAAD patients, and there is a lack of a unified definition and large-scale data to support such analyses. Therefore, exploring this relationship based on large-scale data is of significant clinical importance for optimizing perioperative management, reducing surgical risks, and improving recovery quality. It can provide a scientific basis for clinical decision-making and the rational allocation of medical resources, thereby enhancing the overall prognosis of patients with ATAAD.

Objective

This study aims to investigate the relationship between postoperative MVT and operative mortality in ATAAD patients at our center, identify the characteristics of MVT in patients with poor prognosis, and provide a basis for precisely defining postoperative PMV. Additionally, the study seeks to identify risk factors for PMV and develop a predictive model to assist healthcare providers in early identification of high-risk patients and implementation of targeted respiratory rehabilitation strategies, thereby improving postoperative recovery and prognosis in patients with ATAAD.

Methods

1) This retrospective study included 1049 patients who underwent ATAAD surgery at Nanjing Drum Tower Hospital between 2011 and 2019. Patients were initially divided into five subgroups based on postoperative MVT (<12 hours, 12 to <24 hours, 24 to <48 hours, 48 to <72 hours, and ≥72 hours). Clinical characteristics and outcomes were compared across these subgroups. Multivariable logistic regression analysis was performed to investigate the associations between MVT and adverse events such as surgical mortality and postoperative tracheostomy.

2) Postoperative PMV was defined based on the high-risk intervals of MVT. Clinical characteristics were compared between PMV and non-PMV groups to identify independent risk factors for PMV in ATAAD patients. A nomogram model was developed to visually present the assessment results of these risk factors, aiming to provide a user-friendly risk evaluation tool for clinicians to optimize perioperative management decisions.

Results

Part One

1) This study conducted a retrospective analysis of 1049 patients who underwent surgery for ATAAD at Nanjing Drum Tower Hospital from 2011 to 2019. The overall mortality rate was 11.82% (124 out of 1049), with an average age of 53.02 ± 13.21 years, and 74.83% of the patients were male. Subgroup analysis based on postoperative MVT revealed that patients with longer MVT had more preoperative comorbidities, such as cerebral ischemia and pericardial effusion. These patients also had longer operative times and received more intraoperative blood transfusions. Postoperatively, they were more likely to experience adverse events such as tracheostomy, cerebral ischemia, surgical site infection, and re-exploration.

2) Furthermore, the study population was divided into survivors (n = 925) and non-survivors (n = 124) based on short-term clinical outcomes. Comparing preoperative, intraoperative, and postoperative clinical characteristics of the two groups, we found that the average age of the patients in the mortality group was higher, and the proportion of patients with preoperative pericardial effusion and limb ischemia increased. Myocardial ischemia was more frequently observed in the mortality group, and these patients were more likely to undergo concomitant coronary artery bypass grafting (CABG) during ATAAD surgery. Intraoperative data showed that patients in the mortality group had longer cardiopulmonary bypass (CPB) and aortic cross-clamp (ACC) times, as well as greater intraoperative blood transfusion volumes. Postoperative comparisons also indicated a higher likelihood of complex complications occurring in the mortality group.

3) Logistic regression analysis identified significant risk factors associated with increased operative mortality in ATAAD patients, including advanced age, preoperative pericardial effusion, concomitant CABG, CPB ≥ 208min, higher intraoperative blood transfusion, postoperative cerebral hemorrhage, cerebral infarction, gastrointestinal bleeding, surgical site infection, and MVT ≥ 72 hours.

4) In this study population, 5.00% (52 out of 1049) of patients underwent tracheostomy. Logistic regression analysis revealed that advanced age, postoperative stroke, and MVT ≥ 72 hours were closely associated with an increased risk of postoperative tracheostomy.

Part Two

1) In this study, 26.98% of patients with ATAAD experienced mechanical ventilation for more than 72 hours postoperatively (MVT ≥ 72 hours). These patients were more likely to suffer from severe complications, including tracheostomy, stroke, paraplegia, limb ischemia, surgical site infection, and re-exploration.

2) To further elucidate this phenomenon, we designated MVT ≥ 72 hours as the threshold for PMV and utilized a Logistic regression model to analyze the underlying independent risk factors. The findings revealed that advanced age, preoperative cerebral ischemia, ascending aortic replacement, concomitant CABG, extended CPB duration, and substantial intraoperative fresh frozen plasma transfusion are independent risk factors for PMV. These factors were incorporated into a nomogram model, which demonstrated excellent predictive performance after validation. This model provides a user-friendly tool for clinicians to predict the risk of postoperative PMV in ATAAD patients.

Conclusions

This study demonstrates that PMV (defined as MVT ≥ 72 hours) is a common and severe complication following ATAAD surgery, significantly increasing the risks of operative mortality and adverse events such as reintubation. The findings highlight the critical importance of facilitating safe extubation within 72 hours postoperatively to improve patient outcomes. A nomogram model developed based on large-scale data from ATAAD patients effectively predicts the occurrence of postoperative PMV. This tool provides clinicians with precise guidance to optimize treatment strategies, reduce the risk of PMV, and thereby enhance postoperative recovery and quality of life for patients.