Anastomotic Airway Complications After Lung Transplant: Clinical, Bronchoscopic and CT Correlation

Machine learning model predicts airway stenosis requiring clinical intervention in patients after lung transplantation: a retrospective case-controlled study

BACKGROUND

Patients with airway stenosis (AS) are associated with considerable morbidity and mortality after lung transplantation (LTx). This study aims to develop and validate machine learning (ML) models to predict AS requiring clinical intervention in patients after LTx.

METHODS

Patients who underwent LTx between January 2017 and December 2019 were reviewed. The conventional logistic regression (LR) model was fitted by the independent risk factors which were determined by multivariate LR. The optimal ML model was determined based on 7 feature selection methods and 8 ML algorithms. Model performance was assessed by the area under the curve (AUC) and brier score, which were internally validated by the bootstrap method.

RESULTS

A total of 381 LTx patients were included, and 40 (10.5%) patients developed AS. Multivariate analysis indicated that male, pulmonary arterial hypertension, and postoperative 6-min walking test were significantly associated with AS (all P < 0.001). The conventional LR model showed performance with an AUC of 0.689 and brier score of 0.091. In total, 56 ML models were developed and the optimal ML model was the model fitted using a random forest algorithm with a determination coefficient feature selection method. The optimal model exhibited the highest AUC and brier score values of 0.760 (95% confidence interval [CI], 0.666-0.864) and 0.085 (95% CI, 0.058-0.117) among all ML models, which was superior to the conventional LR model.

CONCLUSIONS

The optimal ML model, which was developed by clinical characteristics, allows for the satisfactory prediction of AS in patients after LTx.

Risk Factors, Incidence, and Outcomes Associated With Clinically Significant Airway Ischemia

Airway complications following lung transplantation remain an important cause of morbidity and mortality. We aimed to identify the incidence, risk factors and outcomes associated with clinically significant airway ischemia (CSAI) in our center. We reviewed 217 lung transplants (386 airway anastomoses) performed at our institution between February 2016 and December 2020. Airway images were graded using the 2018 ISHLT grading guidelines modified slightly for retrospective analysis. Airways were considered to have CSAI if they developed ischemia severity >B2, stenosis >50%, and/or any degree of dehiscence within 6-months of transplant. Regression analyses were used to evaluate outcomes and risk factors for CSAI. Eighty-two patients (37.8%) met criteria for CSAI. Of these, twenty-six (32%) developed stenosis and/or dehiscence, and 17 (21%) required interventions. Patients with CSAI had lower one-year (80.5% vs. 91.9%, p = 0.05) and three-year (67.1% vs. 77.8%, p = 0.08) survival than patients without CSAI. Factors associated with CSAI included younger recipient age, recipient diabetes, single running suture technique, performance of the left anastomosis first, lower venous oxygen saturation within 48-h, and takeback for major bleeding. Our single-center analysis suggests that airway ischemia remains a major obstacle in contemporary lung transplantation. Improving the local healing milieu of the airway anastomosis could potentially mitigate this risk.

Imaging Course of Lung Transplantation: From Patient Selection to Postoperative Complications

Lung transplant is increasingly performed for the treatment of end-stage lung disease. As the number of lung transplants and transplant centers continues to rise, radiologists will more frequently participate in the care of patients undergoing lung transplant, both before and after transplant. Potential donors and recipients undergo chest radiography and CT as part of their pretransplant assessment to evaluate for contraindications to transplant and to aid in surgical planning. After transplant, recipients undergo imaging during the postoperative hospitalization and also in the long-term outpatient setting. Radiologists encounter a wide variety of conditions leading to end-stage lung disease and a myriad of posttransplant complications, some of which are unique to lung transplantation. Familiarity with these pathologic conditions, including their imaging findings and their temporal relationship to the transplant, is crucial to accurate radiologic interpretation. Knowledge of the surgical techniques and expected postoperative appearance prevents confusing normal posttransplant imaging findings with complications. A basic understanding of the indications, contraindications, and surgical considerations of lung transplant aids in imaging interpretation and protocoling and also facilitates communication between radiologists and transplant physicians. Despite medical and surgical advances over the past several decades, lung transplant recipients currently have an average posttransplant life expectancy of only 6.7 years. As members of the transplant team, radiologists can help maximize patient survival and hopefully increase posttransplant life expectancy and quality of life in the coming decades. ^©RSNA, 2021 An invited commentary by Bierhals is available online. Online supplemental material is available for this article.

Imaging Assessment of Complications from Transplantation from Pediatric to Adult Patients: Part 1: Solid Organ Transplantation

End-stage organ failure is commonly treated with transplantation of the respective failing organ. Although outcomes have progressively improved over the decades, early and late complications do occur, and are often diagnosed by imaging. Given the increasing survival rates of transplant patients, the general radiologist may encounter these patients in the outpatient setting. Awareness of the normal radiologic findings after transplantation, and imaging findings of the more common complications, is therefore important. We review and illustrate the imaging assessment of complications from lung, liver, and renal transplantation, highlighting the key similarities and differences between pediatric and adult patients.

Imaging Evaluation of Airway Complications After Lung Transplant

Airway complications (ACs) after lung transplant remain a challenge and include bronchial dehiscence, bronchial stenosis, tracheobronchomalacia, infections, and bronchial fistulas. The spectrum of complications may coexist along a continuum and can be classified as early (<1 month after transplant) or late (>1 month), and anastomotic or nonanastomotic. Bronchiolitis obliterans is the most common form of chronic lung allograft rejection. Airway compromise is seen in rare instances of lung torsion, and imaging may provide helpful diagnostic clues. Computed tomography (CT) and bronchoscopy play major roles in the diagnosis and treatment of ACs after lung transplant. Chest CT with advanced postprocessing techniques is a valuable tool in evaluating for airways complications, for initial bronchoscopic treatment planning and subsequent posttreatment assessment. Various bronchoscopic treatment options may be explored to maintain airway patency. The goal of this article is to review imaging findings of ACs after lung transplantation, with emphasis on chest CT and bronchoscopic correlation.