Pulmonary embolism and pulmonary infarction after lung transplantation

Pulmonary Embolism Following Lung Transplantation: Prevention and Management

Thromboembolic events are the third leading cardiovascular diagnosis following stroke and myocardial infarction. In the United States, 300,000 to 600,000 people per year are diagnosed with venous thromboembolism, either deep venous thrombosis or pulmonary embolism (PE). Of those patients, thousands die from PE despite heightened vigilance and improved therapies. Lung transplant recipients are at increased risk of developing PE due to multiple risk factors unique to this population. Additionally, the transplant recipients are more susceptible to morbid complications from PE. As a result, prevention, timely recognition, and intervention of PE in the lung transplant population are of the utmost importance.

Pulmonary transplant complications: a radiologic review

Lung transplantation has become the definitive treatment for end stage respiratory disease. Numbers and survival rates have increased over the past decade, with transplant recipients living longer and with greater comorbidities, resulting in greater complexity of care. Common and uncommon complications that occur in the immediate, early, intermediate, and late periods can have significant impact on the course of the transplant. Fortunately, advancements in surgery, medical care, and imaging as well as other diagnostics work to prevent, identify, and manage complications that would otherwise have a negative impact on survivability. This review will focus on contextualizing complications both categorically and chronologically, with highlights of specific imaging and clinical features in order to inform both radiologists and clinicians involved in post-transplant care.

The Association of Post-Lung Transplant Pulmonary Embolism With the Development of Chronic Lung Allograft Dysfunction

Background

Pulmonary embolism (PE) is a rare yet serious postoperative complication for lung transplant recipients (LTRs). The association between timing and severity of PE and the development of chronic allograft lung dysfunction (CLAD) has not been described.

Methods

A single-center, retrospective cohort analysis of first LTRs included bilateral or single lung transplants and excluded multiorgan transplants and retransplants. PEs were confirmed by computed tomography angiography or ventilation/perfusion (VQ) scans. Infarctions were confirmed on computed tomography angiography by a trained physician. The PE severity was defined by the Pulmonary Embolism Severity Index (PESI) score, a 30-d post-PE mortality risk calculator, and stratified by low I and II (0-85), intermediate III and IV (85-125), and high V (>125). PE and PESI were analyzed in the outcomes of overall survival, graft failure, and chronic lung allograft dysfunction (CLAD).

Results

We identified 57 of 928 patients (6.14%) who had at least 1 PE in the LTR cohort with a median follow-up of 1623 d. In the subset with PE, the median PESI score was 85 (75.8-96.5). Most of the PESI scores (32/56 available) were in the low-risk category. In the CLAD analysis, there were 49 LTRs who had a PE and 16 LTRs (33%) had infarction. When treating PE as time-dependent and adjusting for covariates, PE was significantly associated with death (hazard ratio [HR] 1.8; 95% confidence interval [CI], 1.3-2.5), as well as increased risk of graft failure, defined as retransplant, CLAD, or death (HR 1.8; 95% CI, 1.3-2.5), and CLAD (HR 1.7; 95% CI, 1.2-2.4). Infarction was not associated with CLAD or death. The PESI risk category was not a significant predictor of death or CLAD.

Conclusions

PE is associated with decreased survival and increased hazard of developing CLAD. PESI score was not a reliable predictor of CLAD or death in this lung transplant cohort.

Limited Effect of Prevention Strategies on Incidence of Clinically Detectable Venous Thromboembolism After Lung Transplantation

BACKGROUND

Thromboembolic complications are common post-lung transplant, leading to significant morbidity. We instituted multiple interventions because of an observed 36.8% incidence of venous thromboembolism (VTE) (Incidence rate (IR) 5.74/1000 pt days) in our recipients.

METHODS

Our initiative commenced January 2015 with enoxaparin initiation within 6-8 hours of intensive care unit arrival and continuation for 4-6 weeks. We evaluated the IR of VTE in lung transplant recipients within 90 days of transplant. In 2017, the protocol was modified to extend the time to initiation of prophylaxis to within 72 hours of ICU arrival. In 2019, we further amended our intraoperative vascular access strategy.

RESULTS

Eighteen of 26 lung transplant recipients (LTR) met inclusion criteria in the 2015 cohort. Six of 18 (33.3%) developed VTE, 50% of which were upper extremity (UE), line associated. Fifty two of 75 LTR were eligible for enoxaparin prophylaxis in the 2017 cohort. Fifteen of 52 subjects (28.8%) developed VTE, 77.8% of which were UE and line associated. Despite improved adherence in 2017, there was little change in VTE IR (3.90/1000 pt days compared with 3.85/1000 pt days). Twenty six of 43 LTR met protocol inclusion criteria in the 2019 cohort. Ten subjects (38.5%) developed VTE, 67% of which were UE and line associated (IR 5.18/1000 pt days).

CONCLUSION

Our prospective study found that LTR remain at high risk for VTE despite aggressive prophylaxis with 4-6 weeks of enoxaparin and adjustment of vascular access approach. Alternative interventions should be investigated to minimize VTE development in this vulnerable population.

The Role of Mechanical Thrombectomy for Acute Massive Pulmonary Embolism in a Patient With Unilateral Lung Transplant and Atrial Septal Defect

PURPOSE

The risk of thromboembolic disease is high in patients with lung transplantation and is associated with significant morbidity and mortality with single healthy transplanted lung. We present a case involving successful endovascular management of life-threatening acute massive pulmonary embolism (PE) in a patient with single lung transplant and atrial septal defect (ASD).

CASE REPORT

A 65-year-old man with a history of interstitial lung disease status post single left orthotopic lung transplant in 2012 presented with acute massive PE and clot burden in the pulmonary arteries of the transplanted left lung. Severe right heart dysfunction, hemodynamic instability, and requirement for vasopressors persisted post systemic thrombolytic therapy. As a result, the patient underwent successful endovascular mechanical thrombectomy with immediate improvement in oxygen saturation and hemodynamic status. The procedure was performed without adverse outcomes or paradoxical embolization despite the presence of ASD. The right heart dysfunction resolved, the patient was extubated the next day, and was discharged to home 2 days post procedure.

CONCLUSIONS

Endovascular mechanical thrombectomy was safely used to treat acute massive PE in a single transplanted lung in the presence of ASD.

CLINICAL IMPACT

Endovascular mechanical thrombectomy could be safely utilized to treat patients with lung transplant and acute massive or submassive pulmonary embolism. However, safely of mechanical thrombectomy should be determined in case-based scenarios and based on time interval from transplantation to when the thrombectomy is required.

Alterations in Pulmonary Physiology with Lung Transplantation

Lung transplant is a treatment option for patients with end-stage lung diseases; however, survival outcomes continue to be inferior when compared to other solid organs. We review the several anatomic and physiologic changes that result from lung transplantation surgery, and their role in the pathophysiology of common complications encountered by lung recipients. The loss of bronchial circulation into the allograft after transplant surgery results in ischemia-related changes in the bronchial artery territory of the allograft. We discuss the role of bronchopulmonary anastomosis in blood circulation in the allograft posttransplant. We review commonly encountered complications related to loss of bronchial circulation such as allograft airway ischemia, necrosis, anastomotic dehiscence, mucociliary dysfunction, and bronchial stenosis. Loss of dual circulation to the lung also increases the risk of pulmonary infarction with acute pulmonary embolism. The loss of lymphatic drainage during transplant surgery also impairs the management of allograft interstitial fluid, resulting in pulmonary edema and early pleural effusion. We discuss the role of lymphatic drainage in primary graft dysfunction. Besides, we review the association of late posttransplant pleural effusion with complications such as acute rejection. We then review the impact of loss of afferent and efferent innervation from the allograft on control of breathing, as well as lung protective reflexes. We conclude with discussion about pulmonary function testing, allograft monitoring with spirometry, and classification of chronic lung allograft dysfunction phenotypes based on total lung capacity measurements. We also review factors limiting physical exercise capacity after lung transplantation, especially impairment of muscle metabolism. © 2023 American Physiological Society. Compr Physiol 13:4269-4293, 2023.

Roles of electrical impedance tomography in lung transplantation

Lung transplantation is the preferred treatment method for patients with end-stage pulmonary disease. However, several factors hinder the progress of lung transplantation, including donor shortages, candidate selection, and various postoperative complications. Electrical impedance tomography (EIT) is a functional imaging tool that can be used to evaluate pulmonary ventilation and perfusion at the bedside. Among patients after lung transplantation, monitoring the graft’s pulmonary function is one of the most concerning issues. The feasible application of EIT in lung transplantation has been reported over the past few years, and this technique has gained increasing interest from multidisciplinary researchers. Nevertheless, physicians still lack knowledge concerning the potential applications of EIT in lung transplantation. We present an updated review of EIT in lung transplantation donors and recipients over the past few years, and discuss the potential use of ventilation- and perfusion-monitoring-based EIT in lung transplantation.

[The bronchial arteries: a small but vital contribution to lung perfusion after lung transplantation]

Blood supply to the lungs is carried out by the pulmonary and bronchial-arterial system. The bronchial-arterial vessels are involved in supplying the small airways all the way up to the terminal bronchioles. The bronchial-arterial system is also necessary for the regulation of airway temperature, humidity and mucociliary clearance. Chronic ischaemia of the small airways due to damage or injury to bronchial arterial supply increases the risk of fibrosis of the small airways (bronchiolitis obliteration), especially in lung transplantation (LTx). Although survival after LTx has improved over time, it is, with a 5-year survival rate of only 50 to 60%, still significantly worse than that of other organ transplants. It is likely that bronchial arterial revascularisation at the time of LTx plays an important transplant-preserving function.

Surgical Complications of Lung Transplantation

Lung transplantation is a life-saving intervention and the most effective therapy for select patients with irreversible lung disease. Despite the effectiveness of lung transplantation, it is a major operation with several opportunities for complications. For example, recipient and donor factors, technical issues, early postoperative events, and immunology can all contribute to potential complications. This article highlights some of the key surgery-related complications that can undermine a successful lung transplantation. The authors offer their expert opinion and experience to help practitioners avoid such complications and recognize and treat them early should they occur.

Venous thromboembolism in lung transplant recipients real world experience from a high volume center

BACKGROUND

Venous thromboembolism (VTE) post lung transplantation is common and has been associated with worse post transplant survival. We report a comprehensive single center review of VTE incidence in the first post transplant year, investigate modifiable risk factors and assess impact on short term outcomes.

METHODS

Retrospective review of all lung transplant recipients between August 2016 to 2018 at Temple University Hospital. Patients were followed for 1 year post transplant. All patients were screened for deep venous thrombosis (DVT) within the first 2 weeks with a venous duplex study. Pre transplant, intra operative, post operative variables, and peri-operative practice patterns were compared between VTE positive and VTE negative groups. Logistic regression modeling was used to identify risk factors for early VTE (VTE within 30 days after transplant).

RESULTS

A total of 235 patients were included in the study, 58 patients (24.7%) developed a VTE in the first post transplant year. Median time to diagnosis was 17 days. Of the patients with VTE, 76% had an isolated DVT, 13.5 % had an isolated pulmonary embolism (PE), and 10.3% had concomitant DVT and PE. In a multivariate logistic regression model, cardiopulmonary bypass (CPB) (OR 1.93 p = 0.015) and interruption of VTE prophylaxis (OR 4.42 p < 0.0001) were predictive of early VTE.

CONCLUSION

VTE post lung transplant is common despite the use of prophylactic anticoagulation. CPB use and interruption of DVT prophylaxis are risk factors for early post transplant VTE. Measures to ensure consistent and uninterrupted prophylaxis may help decrease VTE incidence after lung transplantation.

Ventilation perfusion pulmonary scintigraphy in the evaluation of pre-and post-lung transplant patients

Lung transplantation is an established treatment for patients with a variety of advanced lung diseases. Imaging studies play a valuable role not only in evaluation of patients prior to lung transplantation, but also in the follow up of patients after transplantation for detection of complications. After lung transplantation, complications can occur as a result of surgical procedure, pulmonary embolism and ultimately chronic lung allograft dysfunction. Lung scintigraphy, which includes physiologic assessment of lung ventilation and perfusion by imaging, has become an important procedure in the evaluation of these patients, assuming a complementary role to high resolution anatomic imaging (computed tomography [CT]), as well as spirometry. The purpose of this atlas article is to demonstrate the uses of ventilation perfusion scintigraphy in the pre-transplantation setting for surgical planning and in the evaluation of complications post-lung transplantation based upon experience at our institution.

Pulmonary Transplant Salvage Using Ultrasound-Assisted Thrombolysis of Subacute Occlusive Main Pulmonary Artery Embolus

A 53-year-old woman who underwent bilateral lung transplantation 14 months before presented with 2 to 3 weeks of severe exertional dyspnea. Workup revealed a complete embolic occlusion of her left main pulmonary artery related to a femoral deep venous thrombosis. The occlusion did not respond to systemic anticoagulation, and a trial of catheter-directed thrombolysis was pursued. Flow to the left lower lobe was restored after 2 days of thromobolytic therapy. The patient is alive and well at more than 1 year of follow-up.

Imaging features of intrathoracic complications of lung transplantation: What the radiologists need to know

Lung transplantation has been a method for treating end stage lung disease for decades. Despite improvements in the preoperative assessment of recipients and donors as well as improved surgical techniques, lung transplant recipients are still at a high risk of developing post-operative complications which tend to impact negatively the patients’ outcome if not recognised early. The recognised complications post lung transplantation can be broadly categorised into acute and chronic complications. Recognising the radiological features of these complications has a significant positive impact on patients’ survival post transplantation. This manuscript provides a comprehensive review of the radiological features of post lung transplantations complications over a time continuum.

Single Lung Retransplantation for Graft Infarction due to Herniation of Heart

A young woman with terminal respiratory failure due to idiopathic pulmonary hypertension underwent bilateral lung transplantation. The postoperative course was complicated by herniation of the heart through over the cut pericardial edge on left side leading to left-sided graft infarction requiring pneumonectomy. Unable to wean off mechanical ventilation, patient required lobar transplantation on the left side.