Incidence of clinically unsuspected pulmonary embolism in mechanically ventilated lung transplant recipients

Mechanical thrombectomy for acute pulmonary embolism in lung transplant recipients

The rates of pulmonary embolism (PE) are high among lung transplant (LT) recipients. Management is challenging because of elevated bleeding risks and inadequacy of conventional PE risk stratification tools. New percutaneous large bore mechanical thrombectomy catheters are being increasingly used effectively to debulk thrombus and restore flow immediately. We describe the use of mechanical thrombectomy (MT) in 8 LT recipients. All patients were diagnosed with intermediate/high-risk proximal PE involving the allograft and underwent successful MT within 30 hours of diagnosis. Estimated blood loss was between 200 and 450 cc, with 3 patients requiring blood transfusions. Improvement in heart rate and oxygenation was seen in all 8 patients after the procedure. In the 30 days after MT, 7 of 8 patients survived. One patient died from major bleeding occurred 16 days after MT and 5 days after venoarterial extracorporeal membrane oxygenator decannulation. Mechanical thrombectomy may provide a feasible management strategy in select LT recipients with pulmonary embolism.

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.

[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.

Early postoperative complications in lung transplant recipients

Lung transplantation has become an established therapy for end-stage lung diseases. Early postoperative complications can impact immediate, mid-term, and long-term outcomes. Appropriate management, prevention, and early detection of these early postoperative complications can improve the overall transplant course. In this review, we highlight the incidence, detection, and management of these early postoperative complications in lung transplant recipients.

Incidentally found pulmonary embolism: what's the clinician to do?

Incidental pulmonary embolism (IPE) is a management challenge for the unsuspecting clinician. Patients with IPE frequently have signs or symptoms that are unrecognized as PE related, and their clots occur predominantly in the proximal pulmonary vasculature. There is uniformity in recommending anticoagulation for patients with IPE proximal to the subsegmental pulmonary vasculature, but prospective data are not currently available to guide the duration of therapy in this population. Several studies suggest that outcomes, including recurrence, mortality, and bleeding, are similar for patients with IPE and suspected PE, especially among those who also have cancer. Patients with isolated incidental subsegmental pulmonary embolism (ISSPE) are particularly challenging because some studies suggest that they can be managed without anticoagulation. Therefore, an algorithm is proposed to guide the evaluation and treatment of patients with ISSPE.

Percutaneous mechanical thrombectomy for extensive acute lower-extremity deep venous thrombosis in a patient after double-lung transplantation

Venous thromboembolism, which includes deep venous thrombosis (DVT) and pulmonary embolism (PE), has been estimated to affect 25% of patients after major surgery; however, the literature on venous thromboembolism after thoracic transplantation and optimal approach remains limited. We report the status of a 67-year-old female who developed massive right lower-extremity DVT after double-lung transplantation. Because her surgery had taken place a week before this event, it was decided that pharmaco-thrombolysis was contraindicated due to the high risk of bleeding complications in a fresh double-lung transplant recipient. The patient was taken emergently to the operating room for percutaneous mechanical thrombectomy, which provided grade III (complete lysis) and restored venous patency in the affected extremity. This report highlights the successful use of purely percutaneous mechanical thrombectomy for acute DVT in a double-lung recipient, and also advocates inferior vena cava filter placement to prevent embolic events during the mechanical thrombectomy.

Laser-targeted photosensitizer-induced lung injury: noninvasive rat model of pulmonary infarction

Pulmonary infarction is a life-threatening lung injury that requires rapid and accurate diagnosis for proper treatment. Targetable and reproducible small-animal models that would allow experimental development and preclinical evaluation of diagnostic methods for detecting pulmonary infarction are critically missing. The authors report here a novel procedure to selectively induce pulmonary infarction by photodestructive laser-light irradiation in a targeted location within a specific lung compartment after administration of a photosensitizer. Histopathological analysis of the illuminated lung tissue revealed massive hemorrhage and vascular occlusion after acute injury localized to the site of irradiation. Collapse of alveolar structure, neutrophil influx, and necrosis were subsequently observed. Computed tomography (CT) scans showed evidence of abnormal density and airspace consolidation in the irradiated area of the lung, but not elsewhere in the lung compartment. Perfusion imaging using 99mTc-labeled macroaggregated albumin by single-photon emission computed tomography revealed diminished scintigraphic signal in the opaque area of infarcted lung tissue. The histological changes, CT findings, and perfusion characteristics of pulmonary infarction are mimicked using laser-irradiated, photosensitizer-mediated photodestruction to selectively induce chronic lung injury in a localized area. This small-animal model can be easily and readily used for targeted induction of pulmonary infarction in a designated area of lung compartment and offers the potential for use in evaluating novel diagnostic and therapeutic methods.

Interventional techniques in the management of airway complications following lung transplantation

The last four decades have seen tremendous advances in the field of pulmonary transplantation. Vast improvements in the areas of surgical transplantation techniques, immunosuppressive agents, and postoperative care have all contributed to improved survival of patients. Advances in noninvasive imaging and bronchoscopy have allowed the pulmonary transplant team to intervene early in patients presenting with airway complications, often using minimally invasive procedures such as endobronchial balloon dilation or stent placement, or both. Stent technology itself has also improved and stents may sometimes be customized for treatment of short airway lesions or to optimize continued airflow through the sides of stents by creating openings using balloons or bronchoscopically directed laser. Preliminary work with brachytherapy may be decreasing the need for secondary reinterventions. The authors present an overview of some of these conventional and novel approaches to the treatment of airway complications after lung transplantation.

Pulmonary embolism and pulmonary infarction after lung transplantation

Venous thromboembolism (VTE), which includes pulmonary embolism (PE) and deep vein thrombosis (DVT), is a common occurrence in patients undergoing surgery and is a potentially fatal complication. Especially after lung transplantation, vascular complications can compromise the function of the allograft and limit survival. Typically, the risk of pulmonary infarction after PE in lung transplant recipients is high because the absence or poor development of the collateral bronchial circulation may predispose lung transplant recipients to pulmonary infarction. This article reports 2 cases of PE with associated pulmonary infarction after lung transplantation with significant morbidity.

MDCT evaluation of central airway and vascular complications of lung transplantation

OBJECTIVE

The purpose of this article is to illustrate the spectrum of central airway and vascular complications in lung transplantation using MDCT, with an emphasis on the usefulness of advanced postprocessing techniques.

CONCLUSION

MDCT is an invaluable tool in the diagnosis, evaluation, and posttreatment assessment of central airway and vascular complications in lung transplant recipients. Advanced postprocessing techniques provide complementary information that is visually accessible and anatomically meaningful for the clinician.

Pulmonary embolism at multi-detector row CT of chest: one-year survival of treated and untreated patients

PURPOSE

To retrospectively assess outcome in patients with clinically unsuspected pulmonary embolism (PE) at chest multi-detector row computed tomography (CT).

MATERIALS AND METHODS

Institutional review board approval and informed consent were not required. PE was assessed in consecutive CT scans in 1966 patients (mean age, 60 years; range, 15-96 years; male-female ratio, 1.79) and graded with severity score. Studies with true-positive and false-negative radiologic diagnoses were determined. Coexisting morbidity, anticoagulant therapy (ACT), complications, and 1-year outcome were reviewed. Statistical evaluation included Mann-Whitney U test, chi(2) test, Poisson regression, and Kaplan-Meier statistics.

RESULTS

Scans were PE positive in 117 patients. Clinical data review was complete in 96 patients; 63 of 96 patients had malignancy; in 58, PE was not suspected. In 38 of these 58 patients, radiology report findings were false-negative (mean severity score, 20.21 +/- 17.88 [standard deviation] and 9.55 +/- 7.12 for those with true-positive and false-negative findings, respectively; P = .012). Forty-nine patients received therapeutic ACT; 21, prophylactic ACT; and 26, no treatment. PE severity was higher in patients with therapeutic ACT versus those without (P < .001). Bleeding complications were more frequent with therapeutic ACT (two early deaths, five major nonfatal hemorrhages) than without (one minor hemorrhage; P = .037). There were eight early deaths (therapeutic ACT, seven; without ACT, one; P = .037). Positive predictors of early death included severity score >28, use of systemic thrombolytic therapy, occurrence of major hemorrhage, and new-onset cardiac or renal failure (P = .001-.043). Negative predictors were report with false-negative findings and no therapeutic ACT (P = .007-.037). Predictors of late death (n = 25) were older age, malignancy, and renal failure (P = .001-.043).

CONCLUSION

Clinically unsuspected PE may remain undetected at routine chest CT; these patients have favorable short-term outcome without therapeutic ACT.

Suspected and incidental pulmonary embolism on multidetector-row CT: Analysis of technical and morphological factors influencing the diagnosis in a cross-sectional cancer centre patient cohort

AIM

To assess technical and computed tomography (CT) predictors of true-positive (TP) and false-negative (FN) radiological diagnoses in a retrospective patient cohort with pulmonary embolism (PE) in the setting of a cancer centre.

MATERIALS AND METHODS

Two thousand, four hundred and twelve consecutive chest multidetector-row CT images from 1869 patients were reviewed for presence of PE. CT protocols and TP and FN radiological reports were determined and the clinical files reviewed for suspicion of PE. The severity of PE was assessed by an arterial obstruction index. Ancillary pulmonary findings were scored qualitatively and on a lobar basis. Statistical tests included analysis of variance and univariate and multivariate logistic regressions.

RESULTS

Ninety-one out of a total of 111 PE-positive images were included. Thirty-five patients had clinically suspected PE; 56 were not suspected of having PE. Forty-eight patients had TP diagnoses; 43 (39 of whom were not suspected of having PE) had FN radiological diagnoses. FN diagnoses were most frequent in oesophageal (17/19; 89.5%) and standard chest CT (19/35; 54.3%). Pulmonary CT angiography was associated with TP diagnosis (p<0.0001), whereas oesophageal CT was associated with FN diagnosis (p=0.001). Artefacts and arterial attenuation did not influence PE detection (p=0.017 and 0.066 for artefacts and arterial attenuation, respectively). However, the arterial obstruction index strongly predicted PE diagnosis (p=0.001). This was confirmed on multivariate analysis (p=0.041, 0.027 and 0.020 for pulmonary CT angiography, oesophageal protocols and arterial obstruction index, respectively). When stratified for clinically unsuspected cases, the arterial obstruction index remained the only predictor of PE diagnosis (p=0.009).

CONCLUSION

Predictors of PE diagnosis were PE severity and technical factors; the latter were linked to clinical suspicion of PE. Arterial enhancement appears unlikely to contribute to missed diagnoses, if judged adequate for diagnosis of PE, and ancillary chest findings are unlikely to improve embolus detection.

High Prevalence of Pulmonary Arterial Thrombi in Donor Lungs Rejected for Transplantation

BACKGROUND

Donor hypoxemia is a common reason for the rejection of lungs for transplantation. Organ donors are at high risk for venous thromboembolism. Pulmonary arterial thrombosis could contribute to donor hypoxemia. The primary objective of this study was to prospectively quantify the incidence of pulmonary arterial thrombosis in organ donors whose lungs were rejected for transplantation. The secondary objective was to better define the spectrum of histologic abnormalities in the same group of lungs.

METHODS

A complete gross pathologic and histologic analysis of whole lung specimens was done on lungs from 17 donors whose lungs were rejected for transplantation. Lungs had not been flushed with a pulmonary preservation solution.

RESULTS

Overall, 35% of the donors had gross or microscopic evidence of either pulmonary arterial thrombosis, pulmonary infarction, or both. Clinical characteristics, including oxygenation, were not significantly different between donors who had thrombi or infarction and donors who did not. Other pathologic findings included bronchopneumonia (focal or early in 4/17, moderate or severe in 8/17), respiratory bronchiolitis (7/17) and centriacinar emphysema (7/17).

CONCLUSIONS

Pulmonary arterial thrombosis and/or pulmonary infarction are very common in organ donors whose lungs are rejected for transplantation and might contribute to lung dysfunction both in lung donors and lung recipients. Further studies are needed to define the incidence of pulmonary arterial thrombosis in organ donors whose lungs are used for transplantation and to better assess the adverse clinical consequences of donor pulmonary arterial thrombosis in lung recipients.

Lung transplantation and interstitial lung disease

PURPOSE OF REVIEW

Interstitial lung disease includes a heterogeneous group of disorders that leads to respiratory insufficiency and death in a significant number of patients. Lung transplantation is a therapeutic option in select candidates.

RECENT FINDINGS

The indications, transplant procedure options, and outcomes continue to evolve. Various recipient comorbidities influence the choice of procedure in patients with interstitial lung disease. Single lung transplants are used as the procedure of choice and bilateral transplants are reserved for patients with suppurative lung disease and patients with pulmonary hypertension. Issues unique to patients with interstitial lung disease affect the morbidity, mortality and recurrence of the disease.

SUMMARY

Lung transplantation is an effective therapy for respiratory failure in interstitial lung disease with survival following transplant being similar to that achieved in transplant recipients with other diseases.