Regional distribution of lung perfusion and ventilation at rest and during steady-state exercise after unilateral lung transplantation

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.

Pulmonary Perfusion Changes Following Single-Lung Transplantation

Following single-lung transplantation (SLT), there is significant redistribution of flow preferentially to the transplanted lung. Altered lung perfusion leads to unusual results when performing pulmonary scintigraphy, which could result in interpretation errors. We present pulmonary scintigraphy images from a 67-year-old female patient with history of chronic obstructive pulmonary disease that were obtained before SLT, 10 days after SLT, and 3 months after SLT.

Probable Phaeoacremonium parasiticum as a cause of cavitary native lung nodules after single lung transplantation

Lung nodules after lung transplantation most often represent infection or post-transplant lymphoproliferative disorder in the allograft. Conversely, native lung nodules in single lung transplant recipients are more likely to be bronchogenic carcinoma. We present a patient who developed native lung cavitary nodules. Although malignancy was anticipated, evaluation revealed probable Phaeoacremonium parasiticum infection. Phaeoacremonium parasiticum is a dematiaceous fungus first described as a cause of soft tissue infection in a renal transplant patient. Lung nodules have not been previously described and this is the first case, to our knowledge, of P. parasiticum identified after lung transplantation.

Lung transplantation and lung volume reduction surgery

Since the publication of the last edition of the Handbook of Physiology, lung transplantation has become widely available, via specialized centers, for a variety of end-stage lung diseases. Lung volume reduction surgery, a procedure for emphysema first conceptualized in the 1950s, electrified the pulmonary medicine community when it was rediscovered in the 1990s. In parallel with their technical and clinical refinement, extensive investigation has explored the unique physiology of these procedures. In the case of lung transplantation, relevant issues include the discrepant mechanical function of the donor lungs and recipient thorax, the effects of surgical denervation, acute and chronic rejection, respiratory, chest wall, and limb muscle function, and response to exercise. For lung volume reduction surgery, there have been new insights into the counterintuitive observation that lung function in severe emphysema can be improved by resecting the most diseased portions of the lungs. For both procedures, insights from physiology have fed back to clinicians to refine patient selection and to scientists to design clinical trials. This section will first provide an overview of the clinical aspects of these procedures, including patient selection, surgical techniques, complications, and outcomes. It then reviews the extensive data on lung and muscle function following transplantation and its complications. Finally, it reviews the insights from the last 15 years on the mechanisms whereby removal of lung from an emphysema patient can improve the function of the lung left behind.

Late unilateral pulmonary edema in single lung transplant recipients

In this study we describe 3 single lung transplant recipients who developed unilateral pulmonary edema in the setting of cardiac and renal dysfunction. All 3 patients responded to diuresis with clinical and radiographic improvement. Unilateral cardiogenic pulmonary edema should be considered in the differential diagnosis of dyspnea and unilateral radiographic infiltrates in single lung transplant recipients.

Pulmonary blood flow is inhomogeneously reduced after Euro Collins-preservation and lung transplantation

BACKGROUND

Vasoconstriction after lung transplantation is a well-known phenomenon, but only limited information is available on blood flow distribution after ischemia and reperfusion. The aim of our study was to determine the regional flow characteristics in transplanted and native dog lungs after 24 hours of cold storage and preservation with Euro Collins-solution.

METHODS

Six pairs of weight-matched Foxhounds (25 to 30 kg) were used. In donors and recipients, aortic and pulmonary artery catheters were inserted percutaneously and a reference withdrawal catheter was placed into the main pulmonary artery. For preservation, the lungs were perfused with modified Euro Collins-solution and stored at 4 degrees C. After 24 hours, the left lung was transplanted. Regional pulmonary blood flow was assessed by injection of colored microspheres into the right atrium using the reference withdrawal technique. Measurements of regional pulmonary blood flow were conducted twice in donors and recipients (baseline and 3 hours after reperfusion). Tissue samples from five distinct regions (apical, medial, dorsal, ventral, and lateral) were taken to assess regional pulmonary blood flow and wet-dry ratios.

RESULTS

The relative (per thousand Confidence Intervals/100 mg dry weight) regional pulmonary blood flow was significantly reduced in the transplanted lung but not in the native organ. This reduction was most pronounced in apical regions and smallest in regions close to the hilum. Edema formation occurred in both lungs, as judged from wet-to-dry ratios of lung tissue specimen.

CONCLUSIONS

Two separate processes can be observed after single lung transplantation: (1) reduced regional pulmonary blood flow, which is a regional phenomenon restricted to the transplanted organ, and (2) extensive edema affecting both the transplanted and the native lung.

Calculation of lung flow differential after single-lung transplantation: a transesophageal echocardiographic study

Single-lung transplantation (SLT) is a viable option for patients with end-stage pulmonary disease. After successful SLT, pulmonary blood flow is preferentially shifted to the transplanted lung, creating a flow differential. Lack of flow differential may be indicative of potential vascular complications such as anastomotic stenosis or thrombosis. To assess the ability of transesophageal echocardiography (TEE) in estimating lung flow differential in patients undergoing SLT, biplane TEE was prospectively performed in 18 consecutive patients undergoing SLT early (24 to 72 hours), and in 10 of them late (3 to 6 months) after surgery. Right and left pulmonary vein flow were calculated as Qnu=A. VTI, where A, the pulmonary vein area, was derived as pi.(D/2)(2) and VTI is the velocity time integral of the pulmonary vein spectral display. Lung flow differential was calculated as the ratio of right (RQnu) or left (LQnu) pulmonary vein flow to total pulmonary venous flow (RQnu + LQnu). Lung perfusion imaging scintigraphy (technetium-99m) was used for comparison. Pulmonary vein velocity time integral of transplanted lung was significantly greater than that of native lung (34 +/- 9 vs 18 +/- 8 cm, p <0.001). Percent differential lung flow derived by perfusion imaging scintigraphy and by TEE showed a good correlation (r = 0.67, p <0.001). Pulmonary artery anastomoses were seen in all 12 right-lung recipients, and in 4 of the 6 left-lung recipients; no significant stenosis was noted in the arteries visualized. The pulmonary venous anastomoses were imaged in all patients. Small, nonocclusive pulmonary vein thrombi were seen in 1 patient. In conclusion, TEE is a useful method for calculating lung flow differential in patients undergoing SLT. In addition, TEE provides superb direct visualization of the venous and arterial anastomoses in most patients. Contrary to previous reports, the overall incidence of anastomotic complications is relatively low.

The role of magnetic resonance imaging and spectroscopy in transplantation: from animal models to man

Critical success factors in solid organ and vascular transplantation are the assessment of graft status/viability as well as stringent monitoring of transplant recipients, preferentially using noninvasive techniques. This review addresses the application of magnetic resonance imaging (MRI) and spectroscopy (MRS) in the field of transplantation. The first section is devoted to the description of the main MR techniques used for monitoring the status of the graft noninvasively. Subsequently, the role of MRI/MRS in the analysis of the viability of organs for transplantation is discussed. Since chronic rejection remains a major difficulty, development of new therapies is still ongoing. Thus, the third part is devoted to the use of MRI/MRS for monitoring graft rejection in animal models of transplantation. This is followed by a discussion of clinical studies of transplantation involving MRI/MRS. Finally, a general appraisal is made on available imaging techniques for the non-invasive characterization of grafts in situ, highlighting the role of MR methods in the field of transplantation.

Cardiopulmonary exercise testing before and after lung and heart-lung transplantation

Heart-lung (HLT) and lung transplantation (LT) have been shown to be effective procedures for patients with end-stage cardiopulmonary disorders. As yet, few data exist on the exercise performance of patients before and after thoracic transplantation except with regard to 6-min walk tests. In this article we report cardiopulmonary exercise test results of lung and heart-lung transplant recipients in comparison with their pretransplant values. We studied 103 consecutive recipients of single-lung (n = 46), bilateral lung (n = 32), and heart-lung (n = 25) transplants. Cardiopulmonary exercise testing with a cycle ergometer was performed before and shortly after surgery. Before transplantation, all patients showed severe exercise intolerance and markedly impaired parameters reflecting cardiopulmonary function (e.g., work capacity: 20 +/- 11% predicted; oxygen uptake: 34 +/- 12% predicted; oxygen pulse: 50 +/- 18% predicted; functional dead space ventilation: 57 +/- 10% of minute ventilation; alveolar-arterial oxygen difference during exercise: 79 +/- 15 mm Hg). At 55 +/- 9 d after transplantation, transplant recipients reached maximum oxygen uptakes in the range of 22 to 71% of predicted values; the peak oxygen uptake was increased after transplantation (13.1 +/- 3.4 ml/min/kg versus 10.4 +/- 3.8 ml/min/kg; p < 0.001). Work capacity, oxygen pulse, tidal volume, and peak minute ventilation did not differ in patients following single- or double-lung tranplantation or HLT. Ventilatory factors did not appear to limit exercise capacity in any group. Despite the persistent limitations in aerobic capacity and work rate seen in many of the recipients, cardiopulmonary performance is reasonably well restored shortly after LT and HLT.

Lung perfusion demonstrated by contrast-enhanced dynamic magnetic resonance imaging. Application to unilateral lung transplantation

RATIONALE AND OBJECTIVES

The authors evaluate the use of magnetic resonance (MR) to image pulmonary perfusion in healthy controls and to detect pulmonary defects in patients with unilateral lung transplantation, using dynamic images after contrast administration.

METHODS

Five patients with right lung transplantation and nine healthy volunteers underwent MR imaging. Twenty-five subsecond contrast-enhanced MR images (turbo-fast low-angle shot [FLASH]) were obtained at the level of the pulmonary arteries after a single injection of gadopentetate dimeglumine (0.1 mmol/kg) in an antecubital vein. Perfusion lung scintigraphy was done within 24 hours after the MR imaging examination in the transplanted patients.

RESULTS

Before administration of contrast material, MR images showed both lungs to be homogeneous and of low signal intensity in healthy controls and in patients with lung transplantation. After contrast administration in controls, the mean signal intensity of the dependent lung increased markedly to 171 +/- 24% above baseline, whereas the nondependent signal intensity lung increased by only 105 +/- 17%; these changes were significantly different. In all patients with lung transplantation, a clear perfusion defect was demonstrated in the native lung. This defect was confirmed in all cases by perfusion nuclear scintigraphy, which showed that the majority of lung perfusion is directed to the transplanted allograft, compared with the native contralateral lung.

CONCLUSIONS

Our results suggest that dynamic contrast-enhanced MR imaging is a potential method for detecting pulmonary perfusion defects in patients with lung transplantation.

Single lung transplantation for chronic obstructive pulmonary disease: pulmonary function and impact of bronchiolitis obliterans syndrome

Chronic obstructive pulmonary disease (COPD) is now the most common indication for single lung transplantation. In long-term follow-up, obliterative bronchiolitis is a major problem. The aim of the present study was to perform a long-term follow-up of the pulmonary function and to examine the effect of development of bronchiolitis obliterans syndrome (BOS). Nineteen patients with end-stage COPD underwent single lung transplantation and were followed regularly with pulmonary function tests, and ventilation and perfusion scintigraphy (mean observation time 29 months). They were divided into two categories, with and without BOS, using the definition recommended by the International Society for Heart and Lung Transplantation working group. A mixed model analysis of variance with BOS as co-variate was used to evaluate its effect on pulmonary function. Spirometry, lung transfer factor for carbon monoxide (TLCO), arterial blood gases and 6-min walk test improved significantly (P < 0.001) from before transplantation to 3 months after transplantation. Nine patients developed BOS. Implied by the definition of the syndrome, forced expiratory volume in 1 s (FEV1) was significantly (P < 0.001) lower for patients with BOS while there was no significant effect of BOS category on TLCO corrected for alveolar volume (VA) or perfusion to transplant. Patients without BOS maintained their pulmonary function, and ventilation and perfusion to transplant for more than 3 yr after transplantation. The present results suggest that decreasing FEV1 accompanied by an unchanged TLCO/VA and pulmonary perfusion support the diagnosis of BOS after single lung transplantation for COPD.

Utility of inhaled pentamidine prophylaxis in lung transplant recipients

The incidence of Pneumocystis carinii pneumonia (PCP) has been shown to be high posttransplantation in the absence of prophylaxis. For this reason, lung transplant recipients routinely receive prophylaxis. We report on our results using aerosolized pentamidine prophylaxis in nine patients post-lung transplantation (eight single lung transplants, one double). The patients received monthly treatments of 300 mg of aerosolized pentamidine for a mean of 10.6 months (range, 4 to 21 months). Patients were routinely monitored with serial pulmonary function studies and bronchoscopy as clinically indicated. Two of the patients experienced bronchospasm in response to the therapy. None of the patients experienced any episodes of PCP during the period of inhaled pentamidine prophylaxis. Inhaled pentamidine is a safe and effective form of PCP prophylaxis and may be used instead of sulfamethoxazole-trimethoprim in patients who have a sulfa allergy or other untoward sulfa side effects.