Single lung transplantation for primary pulmonary hypertension

Single Lung Transplant for Secondary Pulmonary Hypertension: The Right Option for the Right Patient

Introduction: The optimal treatment for Secondary Pulmonary Hypertension from End-Stage Lung Disease remains controversial. Double Lung Transplantation is widely regarded as the treatment of choice as it eliminates all diseased parenchyma and introduces a large volume of physiologically normal allograft. By comparison, the role of single lung transplantation for pulmonary hypertension (PAH) is less clear. The remaining diseased lung will limit clinical improvements and permit downstream sequelae; including residual cough, recurrent infection, and continued pulmonary hypertension. But not every patient can undergo DLT. Advanced age, frailty, co-morbid conditions, and limited availability of organs will all affect surgical candidacy and can offset the benefits of double lung procedures. Studies that compare SLT and DLT do not commonly explore the utility of single lung procedures even though multiple theoretical advantages exist; including reduced waiting times, less waitlist mortality, fewer surgical complications, and lower operative mortality. Worse, multiple forms of publication and selection bias may favor DLT in registry-based studies. In this review, we present the prevailing literature on single and double lung transplants in patients with secondary pulmonary hypertension and clarify the potential utility of these procedures. Materials and Methods: A PubMed search for English-language articles exploring single and double lung transplants in the setting of secondary pulmonary hypertension was conducted from 1990 to 2023. Key words included "single lung transplant", "double lung transplant", "pulmonary hypertension", "rejection", "complications", "extracorporeal membranous oxygenation", "death", and all appropriate Boolean operators. We prioritized research from retrospective studies that evaluated clinical outcomes from single centers. Conclusions: The question is not whether DLT is better at resolving lung disease; instead, we must ask if SLT is an acceptable form of therapy in a select group of high-risk patients. Further research should focus on how best to identify recipients that may benefit from each type of procedure, and the clinical utility of perioperative VA ECMO.

Advanced Circulatory Support and Lung Transplantation in Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a progressive fatal disease. Although medical therapies have improved the outlook for these patients, there still exists a cohort of patients with PAH who are refractory to these therapies. Lung transplantation (LT), and in certain cases heart-lung transplantation (HLT), is a therapeutic option for patients with severe PAH who are receiving optimal therapy yet declining. ECMO may serve as a bridge to transplant or recovery in appropriate patients. Although, the mortality within the first 3 months after transplant is higher in PAH recipients than the other indications for LT, and the long-term survival after LT is excellent for this group of individuals. In this review, we discuss the indications for LT in PAH patients, when to refer and list patients for LT, the indications for double lung transplant (DLT) versus HLT for PAH patients, types of advanced circulatory support for severe PAH, and short and long-term outcomes in transplant recipients with PAH.

Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic and progressive disease leading to right heart failure and ultimately death if untreated. The first classification of PH was proposed in 1973. In 2008, the fourth World Symposium on PH held in Dana Point (California, USA) revised previous classifications. Currently, PH is devided into five subgroups. Group 1 includes patients suffering from idiopathic or familial PAH with or without germline mutations. Patients with a diagnosis of PAH should systematically been screened regarding to underlying mutations of BMPR2 gene (bone morphogenetic protein receptor type 2) or more rarely of ACVRL1 (activine receptor-like kinase type 1), ENG (endogline) or Smad8 genes. Pulmonary veno occusive disease and pulmonary capillary hemagiomatosis are individualized and designated as clinical group 1'. Group 2 'Pulmonary hypertension due to left heart diseases' is divided into three sub-groups: systolic dysfonction, diastolic dysfonction and valvular dysfonction. Group 3 'Pulmonary hypertension due to respiratory diseases' includes a heterogenous subgroup of respiratory diseases like PH due to pulmonary fibrosis, COPD, lung emphysema or interstitial lung disease for exemple. Group 4 includes chronic thromboembolic pulmonary hypertension without any distinction of proximal or distal forms. Group 5 regroup PH patients with unclear multifactorial mechanisms. Invasive hemodynamic assessment with right heart catheterization is requested to confirm the definite diagnosis of PH showing a resting mean pulmonary artery pressure (mPAP) of ≥ 25 mmHg and a normal pulmonary capillary wedge pressure (PCWP) of ≤ 15 mmHg. The assessment of PCWP may allow the distinction between pre-capillary and post-capillary PH (PCWP > 15 mmHg). Echocardiography is an important tool in the management of patients with underlying suspicion of PH. The European Society of Cardiology and the European Respiratory Society (ESC-ERS) guidelines specify its role, essentially in the screening proposing criteria for estimating the presence of PH mainly based on tricuspid regurgitation peak velocity and systolic artery pressure (sPAP). The therapy of PAH consists of non-specific drugs including oral anticoagulation and diuretics as well as PAH specific therapy. Diuretics are one of the most important treatment in the setting of PH because right heart failure leads to fluid retention, hepatic congestion, ascites and peripheral edema. Current recommendations propose oral anticoagulation aiming for targeting an International Normalized Ratio (INR) between 1.5-2.5. Target INR for patients displaying chronic thromboembolic PH is between 2–3. Better understanding in pathophysiological mechanisms of PH over the past quarter of a century has led to the development of medical therapeutics, even though no cure for PAH exists. Several specific therapeutic agents were developed for the medical management of PAH including prostanoids (epoprostenol, trepoprostenil, iloprost), endothelin receptor antagonists (bosentan, ambrisentan) and phosphodiesterase type 5 inhibitors (sildenafil, tadalafil). This review discusses the current state of art regarding to epidemiologic aspects of PH, diagnostic approaches and the current classification of PH. In addition, currently available specific PAH therapy is discussed as well as future treatments.

Transplantation for Idiopathic Pulmonary Arterial Hypertension

Background—

Lung transplantation and heart-lung transplantation represent surgical options for treatment of medically refractory idiopathic pulmonary arterial hypertension. The effect of the lung allocation score on wait-list and transplantation outcomes in patients with idiopathic pulmonary arterial hypertension is poorly described.

Methods and Results—

Adults diagnosed with idiopathic pulmonary arterial hypertension and listed for transplantation in the 80 months before and after the lung allocation score algorithm was implemented (n=1430) were identified in the United Network for Organ Sharing thoracic registry. Patients were stratified by organ listed and pre– and post–lung allocation score era. The cumulative incidences of transplantation and mortality for wait-listed patients in both eras were appraised with competing outcomes analysis. Posttransplantation survival was assessed with the Kaplan-Meier method. These analyses were repeated in propensity-matched subgroups. Cox proportional hazards analysis evaluated the effect of prelisting and pretransplantation characteristics on mortality. We found that patients in the post–lung allocation score era had significantly worse comorbidities; nevertheless, both lung transplantation and heart-lung transplantation candidates in this era enjoyed lower wait-list mortality and a higher incidence of transplantation in unmatched and propensity-matched analyses. On multivariable analysis, heart-lung transplantation and double-lung transplantation were associated with improved survival from the time of wait-listing, as was being listed at a medium- to high-volume institution. Donor/recipient sex matching predicted posttransplantation survival.

Conclusions—

The incidence of transplantation has increased while wait-list mortality has decreased in patients with idiopathic pulmonary arterial hypertension wait-listed for transplantation in the post–lung allocation score era. Both heart-lung transplantation and double-lung transplantation are predictive of survival in transplantation candidates with idiopathic pulmonary arterial hypertension, as is being listed at a medium- to high-volume institution. Donor/recipient sex matching is associated with better posttransplantation survival.

Pulmonary hypertension-"state of the art" management in 2012

Pulmonary artery hypertension (PAH) is a pathological condition of small pulmonary arteries, characterised by vascular proliferation and remodelling. The pulmonary artery pressure and pulmonary vascular resistance progressively rise, leading to right heart failure and death. Pulmonary artery hypertension may be secondary to various conditions, or it may be idiopathic where no underlying cause is identifiable. Earlier, only symptomatic treatment was available for such patients which did not change the natural history of the disease. However, over the years, improvement in understanding the pathogenesis has resulted in the development of targeted approaches to the treatment of PAH. Survival advantage has also been shown with some of the pharmacologic agents. This review article discusses the current management strategy for PAH with special emphasis on an idiopathic variety, in an Indian context.

Lung transplantation for pulmonary hypertension

Although medical therapies for pulmonary arterial hypertension have greatly improved, it remains a chronic and fatal disease. For patients who are refractory to medical therapy, lung transplantation is an important treatment option. This review discusses issues pertaining to indications for transplant, preparation for transplant and listing, operative issues, and outcomes for patients with pulmonary arterial hypertension.

New approaches to the treatment of pulmonary hypertension: from bench to bedside

Pulmonary hypertension (PH) is a severe, life-threatening disease for which there are no effective curative therapies. A diverse group of agents such as prostacyclins, endothelin antagonists, phosphodiesterase inhibitors, calcium channel blockers, diuretics, inotropic agents, and anticoagulants are used to treat PH; however, none of these agents have a marked effect upon survival. Among the new agents that promise treatment of PH are rho-kinase inhibitors and soluble guanylate cyclase stimulators. Although these new classes of agents have beneficial effects in experimental animal models and clinical studies, they are not selective in their actions on the pulmonary vascular bed. This manuscript reviews the actions of rho-kinase inhibitors and soluble guanylate cyclase stimulators on the pulmonary vascular bed. It is our hypothesis that these new agents may be more effective than current therapies in the treatment of PH. Moreover, new methods in the delivery of these agents to the lung need to be developed so that their main effects will be exerted in the pulmonary vascular bed and their systemic effects can be minimized or avoided.

Review: Therapeutic advances in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by vasoconstriction, in situ thrombosis, and vascular remodeling of small pulmonary arteries inducing increased pulmonary arterial resistance. Conventional treatment is based on life style modification and nonspecific treatment (warfarine, diuretics, oxygen). Calcium channel blockers are vasodilatators that have been shown to be of great efficacy in a very specific subpopulation of patients with PAH. For the majority of patients, specific PAH therapies are still lacking. Numerous studies evaluating prostacyclin agonists, endothelin-receptor antagonists, and phosphodiesterase type 5 inhibitors are now available to guide therapeutic choices. Despite those important advances there is still no cure for PAH. Fortunately, research is ongoing and many drugs show promises.

Traitement de l’hypertension artérielle pulmonaire

Pulmonary arterial hypertension (PAH) is characterized by vasoconstriction, in situ thrombosis, and vascular remodeling of small pulmonary arteries. It induces a fixed pulmonary arterial obstruction, persistent elevation of pulmonary arterial resistance, and eventually right heart failure. Conventional therapy is based on simple measures (exercise limitation) and nonspecific treatments (warfarin, diuretics, and oxygen). Pure vasodilators, such as calcium channel blockers, are effective only in a minority of patients who have an acute response to vasodilator testing. Intravenous prostacyclin (epoprostenol) and endothelin receptor blockers have vasodilator and antiproliferative properties. Epoprostenol therapy has significantly improved PAH prognosis and remains the first-line treatment for patients with the most severe disease. Bosentan is an interesting first-line treatment for NYHA functional class III patients. Availability of novel specific drugs (endothelin receptor type A antagonists, prostacyclin analogues, type 5 phosphodiesterase inhibitors) is opening new perspectives in PAH treatment. The long-term benefit of these drugs remains to be evaluated and their respective place in treatment of these patients is still uncertain. The evolution of therapy from vasodilators to antiproliferative agents reflects the advancement in our understanding of the mechanisms mediating pulmonary arterial hypertension.

[Treatments for pulmonary arterial hypertension]

PURPOSE

Pulmonary arterial hypertension (PAH) is characterized by vasoconstriction, in situ thrombosis and vascular remodeling of small pulmonary arteries inducing a fixed pulmonary arterial obstruction and persistent elevation of pulmonary arterial resistance. Conventional treatment is based on simple measures (exercise limitation) and non-specific drugs (warfarine, diuretics, oxygen).

CURRENT KNOWLEDGE AND KEY POINTS

Pure vasodilators like calcium channel antagonists have little or no effect on the vast majority of patients, presumably because fixed pulmonary arteriopathy predominate over vasoconstriction. Intravenous prostacyclin (epoprostenol) and endothelin receptor antagonists have vasodilator and antiproliferative properties. Epoprostenol therapy has resulted in significant improvements in prognosis of this disease and this drug remains the first-line treatment of the most severe patients. Bosentan is an interesting first-line treatment for NYHA functional class III patients. Availability of novel specific drugs (endothelin receptor type A antagonists, prostacyclin analogues, type 5 phosphodiesterase inhibitors) open new perspectives in treatment of PAH. The long-term benefit of these drugs remains to be evaluated and their respective place in treatment of these patients is still uncertain. We here present the different therapeutic alternatives available in the PAH and propose an algorithm for treatment of these patients.

FUTURE PROSPECTS AND PROJECTS

The evolution of therapy from vasodilators to antiproliferative agents reflects the advancement in our understanding of the mechanisms mediating pulmonary arterial hypertension.

Primary pulmonary hypertension: Current therapy

Because the causes of primary pulmonary hypertension (PPH) remains unknown, the therapeutic approach of the disease can be only empirical, based on the pathology and pathobiology of pulmonary circulation. Despite the inability to cure the disease, therapeutic advances over the past 20 years have contributed to an improvement of quality of life and prolonged survival in PPH patients. Current therapeutic approach of PPH mostly includes limitation of physical activity, long-term anticoagulation, and vasodilator therapy. Among all tested oral vasodilators, calcium-channel blockers are the most efficient long-term therapies by improving symptoms and hemodynamics in a subset of PPH patients (10% to 15%) who acutely respond to such drugs. Acute pulmonary vasodilator response to inhalation of nitric oxide can predict acute and chronic responses to oral calcium-channel blockers. A better understanding of the pathogenesis of PPH has changed the focus of medical treatments from purely chronic vasodilator therapy to the evaluation of agents, such as prostaglandins, that may reverse the proliferation of pulmonary vascular cells and result in regression of the pulmonary vascular hypertrophy and remodeling. Long-term treatment with intravenous epoprostenol (prostaglandin I(2) or prostacyclin) improves exercise capacity, hemodynamics and survival in most patients with PPH in functional class NYHA III or IV, and may be currently considered as the "gold standard" therapy for severe patients. However, response to long-term epoprostenol therapy may be incomplete, adverse effects are common, and survival remains unsatisfactory (55% at 5 years). In such patients with severe pulmonary hypertension refractory to medical therapy, atrioseptostomy and lung transplantation can be indicated.

[Pulmonary hypertension associated with connective tissue diseases]

PURPOSE

Pulmonary hypertension is a rare but well-known life-threatening complication of connective tissue diseases. The aim of this article is to analyse the available literature and to report the experience of a pulmonary vascular diseases centre about this complication.

CURRENT KNOWLEDGE AND KEY POINTS

Scleroderma and its limited variant, the CREST syndrome (calcification, Raynaud phenomenon, esophageal dysmotility, sclerodactily, telangiectasia), is the most common connective tissue disease affected by pulmonary hypertension. Dyspnea is the main symptom and is frequently severe. Echocardiography is an excellent exam to detect pulmonary hypertension. However, right heart catheterization is necessary to confirm the diagnosis of pulmonary hypertension and to test vasoreactivity with a potent vasodilator such as nitric oxide. Pulmonary hypertension is less severe in patients with connective tissue diseases perhaps because of an earlier diagnosis. A significantly lower proportion of patients presents an acute vasodilator response, suggesting an early constitution of irreversible pulmonary vascular lesions. Continuous intravenous epoprostenol therapy seems to be less effective as compared with patients with primitive pulmonary hypertension and does not improve survival. So, we observed dramatic improvement in rare cases after immunosuppressive therapy.

FUTURE PROSPECTS AND PROJECTS

New treatments with oral, subcutaneous or inhaled stable prostacyclin analogs or with an endothelin receptor antagonist are currently being evaluated. The role of immunosuppressive therapy has to be defined.

Lung transplantation for primary pulmonary hypertension

Recent progress in medical therapies has diminished the role of transplantation in the management of PPH during the past decade. Drug therapy is not effective in some patients, responses to therapy are not sustained over time in others, and drug side effects eventually limit the benefits of treatment in a few more. Lung transplantation therefore ultimately is the only alternative for patients whose PPH is severe and cannot be managed medically. Choosing the right patient as a transplant candidate and the right time to make the initial referral to a transplant center are the crucial initial steps in the transplantation process, and the long waiting time before transplantation must be integrated into this decision. The outcome of lung and heart-lung transplantation for PHH has been good but sobering. Functional recovery has been excellent, but long-term survival results have been limited by the high prevalence of chronic allograft rejection.

Pulmonary artery systolic pressures estimated by echocardiogram vs cardiac catheterization in patients awaiting lung transplantation

BACKGROUND

At many lung transplant centers, right heart catheterization and transthoracic echocardiogram are part of the routine pre-transplant evaluation to measure pulmonary pressures. Because decisions regarding single vs bilateral lung transplant procedures and the need for cardiopulmonary bypass are often made based on pulmonary artery systolic pressures, we sought to examine the relationship between estimated and measured pulmonary artery systolic pressures using echocardiogram and catheterization, respectively.

METHODS

We retrospectively reviewed all patients in our program who had measured pulmonary hypertension (n = 57). Patients with both echocardiogram-estimated and catheterization-measured pulmonary artery systolic pressures performed within 2 weeks of each other were included (n = 19). We analyzed results for correlation and linear regression in the entire group and in the patients with primary pulmonary hypertension (n = 8) and pulmonary fibrosis (n = 8).

RESULTS

In patients with primary pulmonary hypertension, pulmonary artery systolic pressure was 94 +/- 27 and 95 +/- 15 mm Hg by echocardiogram and catheterization, respectively, with r(2) = 0.11; in patients with pulmonary fibrosis, 57 +/- 23 and 58 +/- 12 mm Hg with r(2) = 0.22; and in the whole group, 76 +/- 29 and 75 +/- 23 mm Hg with r(2) = 0.50. Thirty-two additional patients had mean pulmonary artery systolic pressure = 48 +/- 16 mm Hg by catheterization but either had no evidence of tricuspid regurgitation by echocardiogram (n = 22) or the pulmonary artery systolic pressure could not be measured (n = 10).

CONCLUSIONS

In patients with pulmonary hypertension awaiting transplant, pulmonary artery systolic pressures estimated by echocardiogram correspond but do not serve as an accurate predictive model of pulmonary artery systolic pressures measured by catheterization. Technical limitations of the echocardiogram in this patient population often preclude estimating pulmonary artery systolic pressure.

The effects of single lung transplantation in rats with monocrotaline-induced pulmonary hypertension

Acute haemodynamic change after single lung transplantation for primary pulmonary hypertension was evaluated using a rat transplantation model. Inbred Fisher 344 rats were administered with 40 mg/kg monocrotaline in order to induce pulmonary hypertension. The rats whose mean pulmonary arterial pressure (PAP) was over 30.0 mm Hg received a left lung isograft from a normal donor after right heart catheterization. In the control group, PAP increased after single lung transplantation. On the other hand, in the pulmonary hypertensive group, PAP was significantly decreased 60 min after the transplantation, but 3 and 6 h after the transplantation, the PAP significantly increased again. On the day after the operation, it again decreased significantly. Left-to-right lung blood flow ratio was significantly increased in rats with pulmonary hypertension compared to rats with normal pulmonary pressure on both the 1st and 3rd postoperative days. The oedema of the grafted lung was more severe in the pulmonary hypertensive group than in the control group in the acute phase. In conclusion, single lung transplantation for pulmonary hypertension shifted pulmonary blood perfusion to the grafted lung and this shift made pulmonary oedema of the grafts more severe in the acute phase. These oedematous changes, which were more pronounced in the grafts in the pulmonary hypertensive rats, might have contributed to the transient rise in PAP in those rats after single lung transplantation.

Maximal expiratory flow patterns after single-lung transplantation in patients with and without chronic airways obstruction

BACKGROUND

A biphasic-plateau pattern in the maximal expiratory flow-volume (MEFV) curve has been described after single-lung transplantation (SLT) in patients with chronic airways obstruction (CAO). It has been theorized that this pattern is either related to stenosis at the anastomotic or subanastomotic site, or the sum of the airflow contribution from the native lung with airways obstruction and transplanted lung.

SUBJECTS AND METHODS

We analyzed data in 16 patients with CAO who had undergone transplantations (5 men, 11 women; mean age [+/- SD], 53.8 +/- 4.9 years), and 9 patients with pulmonary vascular disease (PVD) without airways obstruction who had undergone transplantations (2 men, 7 women; mean age, 35.4 +/- 11.4 years).

RESULTS

In the patients with PVD, there were no significant changes in static or dynamic lung volumes or in the MEFV curve after SLT. In the patients with CAO, indexes of airways obstruction improved significantly after SLT, and the typical biphasic-plateau pattern developed in the MEFV curve. In one patient with CAO who required pneumonectomy of the native lung after SLT, the biphasic pattern was absent.

CONCLUSIONS

These results support the view that this MEFV pattern is a result of airflow from the native and transplanted lungs in patients with CAO. In addition, the results show that in patients with no prior airways obstruction, SLT does not alter static or dynamic lung volumes or maximal expiratory flow rate.

Heart-lung transplantation for primary pulmonary hypertension

BACKGROUND

The operation of choice for primary pulmonary hypertension remains controversial, as heart-lung transplantation, single-lung transplantation, and double-lung transplantation have all been advocated.

METHODS

We reviewed our institution's experience with heart-lung transplantation for primary pulmonary hypertension.

RESULTS

Thirty-nine patients had heart-lung transplantation for primary pulmonary hypertension. Operative mortality rate was 18%, and actuarial survival was 72% at 1 year, 67% at 2 years, and 42% at 5 years. Freedom from obliterative bronchiolitis was 91% at 1 year, 83% at 2 years, and 70% at 5 years. Freedom from obliterative bronchiolitis-related death was 100% at 1 year, 90% at 2 years, and 87% at 5 years. Freedom from accelerated graft coronary disease was 92% at 5 years. The most frequent causes of death were infection, obliterative bronchiolitis, and accelerated graft coronary disease.

CONCLUSIONS

Heart-lung transplantation results in survival comparable to that reported for single or double lung transplantation. Obliterative bronchiolitis is a significant cause of late death but seems to occur less frequently with heart-lung transplantation than with lung transplantation alone. Accelerated coronary graft disease is rare in the first 5 years after transplantation.

Endothelial defect mediates attenuated vasorelaxant response to isoproterenol after lung transplantation

We have previously demonstrated that pulmonary vasodilation in response to isoproterenol is attenuated in conscious dogs after left lung autotransplantation (LLA). Our present goal was to identify the cellular mechanism responsible for this dysfunction. Size- and position-matched pulmonary arterial rings were isolated from the right (control) and left (LLA) lungs of 23 dogs 1-14 mo post-LLA. The rings were suspended for isometric tension recording and precontracted, and the vasorelaxant responses to activators of the beta-adrenoreceptor signaling pathway were examined. With the endothelium intact the maximal pulmonary vasorelaxant response to isoproterenol was reduced (P < 0.02) to 57 +/- 9% in LLA rings, compared with 87 +/- 3% in control rings. Responses to the Gs protein activator cholera toxin were also attenuated post-LLA, with the concentration-effect curve shifted to the right (P < 0.01) and no change in the maximal response. In contrast, the vasorelaxant responses to forskolin (adenylyl cyclase activator) or dibutyryl cAMP were similar in endothelium-intact control and LLA rings. In endothelium-denuded rings the maximal vasorelaxant responses to isoproterenol were reduced (P < 0.01) to approximately 25% in both control and LLA rings. In denuded rings cholera toxin, forskolin, and dibutyryl cAMP caused 100% vasorelaxation, and the IC50 values for these agonists were similar in control and LLA rings. Isoproterenol increased (P < 0.05) tissue cAMP to the same extent in control and LLA rings with or without endothelium. In contrast, isoproterenol increased (P < 0.05) tissue cGMP only in endothelium-intact rings, and this effect was reduced (P < 0.05) approximately 50% in LLA rings compared with control. Oxypurinol (endothelial xanthine oxidase inhibitor) restored the pulmonary vasorelaxant response to isoproterenol in endothelium-intact LLA rings. Our results provide the first evidence that activation of the beta-adrenoreceptor signaling pathway in endothelium-intact pulmonary arterial rings results in an increase in cGMP. Moreover, the attenuation in beta-adrenoreceptor-mediated pulmonary vasorelaxation post-LLA is due to inactivation of nitric oxide by endothelium-derived superoxide anion.

Superoxide anion scavengers restore NO-mediated pulmonary vasodilation after lung transplantation

Left lung autotransplantation (LLA) results in a chronic attenuation in endothelium-dependent, nitric oxide (NO)-mediated pulmonary vasodilation. We tested the hypothesis that this abnormality involves a decrease in the effective concentration of NO due to inactivation by superoxide anion. Size- and position-matched pulmonary arterial rings were isolated from the right (control) and left (LLA) lungs of seven dogs 1-5 mo post-LLA. The rings were suspended for isometric tension recording and contracted with phenylephrine, and cumulative dose-response curves for ACh or calcium ionophore (A-23187) were generated. Endothelium-dependent relaxation to ACh was inhibited post-LLA, with the maximum vasorelaxation response reduced from 88 +/- 5 to 63 +/- 5% (P < 0. 01) post-LLA. In contrast, after pretreatment with the superoxide anion scavengers tiron or superoxide dismutase (SOD), the dose-response relationships for ACh were similar in control and LLA rings. Oxypurinol, which inhibits superoxide anion production by endothelial xanthine oxidase, also restored the vasorelaxation response to ACh in LLA rings. The pulmonary vasorelaxant response to A-23187 was also attenuated (P < 0.01) post-LLA, and this effect was entirely reversed by pretreatment with tiron, SOD, or oxypurinol. These results indicate that the attenuated responses to these pulmonary vasorelaxants post-LLA involve inactivation of NO by superoxide anion generated by endothelial xanthine oxidase.

The impact of bronchiolitis obliterans on late morbidity and mortality after single and bilateral lung transplantation for pulmonary hypertension

Primary pulmonary hypertension (PPH) is a rare cardiovascular disease with a variable course; however, in general, its prognosis is poor. Among the various treatment options available, transplantation (initially heart-lung transplantation, and later isolated single or bilateral lung transplantation) has become an accepted modality. Heart-lung transplantation is necessary only in a minority of patients because right ventricular recovery has been gratifying after isolated lung transplantation. Furthermore, the scarcity of suitable donor organs mandates the achievement of the maximal number of heart and lung transplants from the limited donor pool. Available published data show that both single and bilateral lung transplantation are suitable alternatives for the majority of patients with pulmonary hypertension. Bronchiolitis obliterans syndrome (BOS), the main cause of late mortality and morbidity in lung transplant recipients, affects pulmonary hypertensive patients as it does other recipient subgroups. The available data regarding the impact of BOS on single versus bilateral lung recipients with pulmonary hypertension are somewhat scanty. Although some have suggested that BOS is more prevalent among PPH recipients, this is not uniformly supported through the literature. Other reports have documented severe ventilation-perfusion imbalance associated with graft dysfunction secondary to BOS in single lung transplant recipients with PPH. Despite this, there are no available data to document a significant survival benefit for PPH patients receiving bilateral versus single lung transplantation. Our own transplantation experience at Washington University in St. Louis with pulmonary hypertension shows a trend toward better survival in bilateral lung recipients, although this difference is not significant. Ultimately, both single and bilateral lung replacement seem to be satisfactory transplant options in PPH. Both recipient groups are affected by BOS, and longer follow-up of larger numbers of patients may document superior survival and functional outcome with bilateral lung replacement.

Controlling perioperative morbidity and mortality after lung transplantation for pulmonary hypertension

Lung transplantation for pulmonary hypertension now accounts for more than 18% of all transplantations performed with 1-year survival rates for primary pulmonary hypertension approximating 65%. Patients have NYHA class III or IV symptoms and typically have marked right ventricular dysfunction. Accelerated or acute decompensation can occur. A decline in status leads to a patient with severe right heart failure, hepatic dysfunction and severe malnutrition, conditions that increase perioperative morbidity and mortality. Immediate right ventricular dysfunction may be related to allograft injury with persistent elevation of pulmonary artery pressures or to intrinsic right ventricular disease; this can be supported with inotropic medications. Single-lung transplantation results in postoperative physiology that can require aggressive therapy to limit mortality. When allograft dysfunction occurs, significant hypoxemia results to a greater degree than that observed with single-lung transplantations for other diseases or following double-lung transplantation. As a result, careful donor selection for a single lung transplantation is crucial. The most common reason for prolonged ventilation is allograft reperfusion injury with ventilation-perfusion mismatching. Neuromuscular blockade can decrease oxygen utilization and improve chest wall compliance, whereas lateral positioning with the native lung down can be crucial to improving V/Q matching. Differential lung ventilation allows the application of larger quantities of positive end-expiratory pressure to the injured allograft. The use of exogenous nitrates has been advocated to reduce pulmonary vascular resistance. Nitric oxide has attractive potential benefits because it can be delivered directly to the lungs and functions to dilate the pulmonary vascular bed. All else having failed, we and others have successfully used extracorporeal membrane oxygenation to support cardiopulmonary function.

Medical and surgical treatment options for pulmonary hypertension

Significant advances in the treatment of pulmonary hypertension have been achieved in the past decade. Approximately one quarter of patients with primary pulmonary hypertension (PPH) can be effectively managed with chronic calcium channel blocker therapy; for the remainder, transplantation or continuous intravenous epoprostenol are complex but effective approaches. Epoprostenol therapy was initially envisioned as a bridge to transplantation, but recent experience has established this approach as an alternative to transplantation in some patients, with comparable survival rates. Not all patients derive benefit from epoprostenol, however, and adverse effects are common. Accordingly, patients who fall into New York Heart Association Functional Classes III and IV and who are refractory to oral vasodilator therapy should be evaluated both for the initiation of epoprostenol therapy and concurrent listing for transplantation. By delaying or avoiding transplantation through the use of epoprostenol, these patients may also benefit from ongoing research that targets novel therapeutic approaches and less cumbersome delivery mechanisms. Thus, epoprostenol may serve as a bridge to transplantation for some patients and to newer therapeutic options for others.

Lung transplantation. A disease-specific approach

Lung transplantation has emerged as a viable option for the treatment of end-stage disease attributable to a wide spectrum of primary disorders. Although many aspects of patient management are indifferent to the underlying indication, important differences related to timing of transplantation, selection of candidates, choice of procedure, and post-transplant complications exist among the various primary disease groups. Optimal utilization of transplantation for these challenging patient populations with advanced lung disease mandates a thorough appreciation of those differences.

The past, present, and future of lung transplantation

BACKGROUND

The history of lung transplantation from the first human transplant performed in 1963 to the present is reviewed with particular focus on the added challenges because of the contaminated bronchus, exposure of the graft to airborne organisms, the poor blood supply to the bronchus, and the problem of reperfusion pulmonary edema.

METHODS

The technical aspects of single and double sequential lung transplantation are reviewed, as are the current indications for single, double sequential, and heart/lung transplantation. Criteria for lung transplant recipients, in addition to their primary disease are noted, as are absolute and relative contraindications. The standard criteria for donor selection are also reviewed.

RESULTS

The results of single, double sequential, and heart-lung transplantation over the past 10 years as reported by the International Society for Heart and Lung Transplantation Database are reviewed. In addition, the statistics of the lung and heart-lung transplantation program at the University of Colorado Health Sciences Center are reviewed, including the current immunosuppressive regimens and early and late monitoring for infection and rejection. This experience includes 3 early deaths in the first 53 patients for an operative mortality of 5.6%, with a 1-year actuarial survival of 90%.

CONCLUSIONS

During the past decade remarkable improvement in the result of single and double sequential lung transplantation have occurred. As 1-year, actuarial survival is now approaching 90% at some institutions. Living related lobar transplantation, new antirejection agents, chimerism, and xenograft transplantation are areas for continuing and future investigation. The shortage in donor organ supply continues to be a very significant factor in limiting human lung transplantation.

Graft damage after a single lung transplantation for pulmonary hypertension in a rat model

The hemodynamic effect and degree of damage in grafts of single lung transplants for pulmonary hypertension were studied in rats with monocrotaline-induced pulmonary hypertension. Inbred male Lewis rats (weight 200-230 g) were divided into two groups. Group 1 (control group, n = 16) underwent isogenic left lung transplantation, while group 2 (n = 15) received an intravenous administration of monocrotaline (80 mg/kg i.v.) and underwent isogenic left single lung transplantation 3 week later. Hemodynamic evaluations were performed prior to transplantation, at 1 h postoperatively, and on days 3 and 7 after transplantation. Mean pulmonary arterial pressure (mPAP) rapidly declined after transplantation in group 2, from 39.3 +/- 8.7 mmHg to 18.5 +/- 3.0 mmHg 1 h after transplantation, and remained stable on day 7 after transplantation. No significant difference in the mPAP between the two groups was observed after transplantation. The extravascular lung water volume (ELWV: dry/wet ratio) in the right lung of group 2 significantly increased on day 3 (0.86 +/- 0.02) (P < 0.01), and subsequently decreased to control levels on day 7 (0.83 +/- 0.02). There was no significant difference in the ELWV in the grafted lungs between the two groups (0.84 +/- 0.03 vs 0.86 +/- 0.04), but there was tendency toward an increase in ELWV in group 2 on days 3 and 7. These data thus demonstrated that a hemodynamic improvement was obtained by single lung transplantation; however the degree of graft damage was remarkable in the pulmonary hypertension group.

Delayed right heart failure following lung transplantation

Dynamic right ventricular outflow tract obstruction (RVOTO) has been reported following lung transplantation for pulmonary hypertension, usually in association with the use of inotropic agents. This report describes delayed severe right-sided heart failure associated with right ventricular outflow tract obstruction following sequential bilateral lung transplantation and closure of a ventricular septal defect. The patient had no evidence of outflow tract obstruction in the early posttransplant period but developed progressive right heart failure more than 2 months later. Catheterization revealed dynamic RVOTO and an elevated right ventricular end-diastolic pressure. The patient was treated with metoprolol tartrate and diltiazem hydrochloride with resolution of the outflow tract obstruction and heart failure. This case demonstrates that RVOTO can occur in the late posttransplant period and must be included in the differential diagnosis for patients who develop right-sided heart failure.

Pediatric lung transplantation for graft-versus-host disease following bone marrow transplantation

Nine years after receiving a bone marrow transplant for aplastic anemia, a 14-year-old girl with severe pulmonary disease associated with graft-versus-host disease received a double lung transplant. Subsequent to lung transplant, her lung function improved dramatically (FEV1 increasing from 20 to 73 percent predicted normal, residual volume decreasing from 316 to 130 percent predicted normal values). The patient is currently well 15 months after transplant, while receiving immunosuppression consisting of FK506 and azathioprine. Double lung transplantation may offer a therapeutic option for the treatment of graft-versus-host pulmonary disease in selected patients.

Survival in primary pulmonary hypertension. Validation of a prognostic equation

BACKGROUND

The prognosis of patients with primary pulmonary hypertension (PPH) remains a major problem for the planning and assessment of therapeutic interventions. The objectives of this study were (1) to characterize mortality in a Mexican population of patients with PPH and to investigate factors associated with survival and (2) to test the applicability in this population of the prognostic equation proposed by the US National Institutes of Health study on PPH.

METHODS AND RESULTS

A dynamic cohort of patients with PPH at our institution were enrolled between June 1977 and August 1991 and prospectively followed at regular intervals through September 1992. Measurements at diagnosis included hemodynamic and pulmonary function variables in addition to information on demographic data and medical history. The response to vasodilator treatment was also analyzed. The estimated median survival of the group was 4.04 years (95% confidence interval, 2.98 to 5.08 years). Variables associated with poor survival (univariate analysis) included an elevated mean right atrial pressure, a decreased cardiac index, and a decreased mixed venous PO2. A reduced forced vital capacity and the absence of vasodilator treatment were also associated with poor survival. A multivariate Cox proportional-hazards regression analysis was used to assess the adjusted hazard ratios, hence the relative contributions of the variables controlling for confounding. Reduced forced vital capacity and cardiac index and increased right atrial pressure were still significantly associated as risk factors for survival in patients with PPH. Survival as computed by the equation correlated with real survival of PPH patients with positive predictive values of 87%, 91%, and 89% at 1, 2, and 3 years, respectively. The equation, however, was relatively unable to predict deaths in our population, in part because of the strict limits of poor prognosis.

CONCLUSIONS

Mortality in PPH is largely associated with hemodynamic variables that assess right ventricular function. The proposed prognostic equation had a high sensitivity and a relatively low specificity to predict survival in our PPH population. To improve this specificity it may be necessary to increase the limits of poor prognosis as defined by the equation.

Single lung transplantation in patients with systemic disease

OBJECTIVE

To report functional results and survival in patients undergoing single lung transplantation (SLT) for pulmonary involvement associated with systemic disease or prior malignancy, criteria traditionally considered contraindications to SLT.

DESIGN

Case series.

SETTING

The University of Texas Health Science Center at San Antonio.

PATIENTS

Nine patients who have undergone SLT for end-stage lung disease: four patients with sarcoidosis; two patients with limited scleroderma; and three patients with prior malignancies (two with prior lymphoma and bleomycin-induced pulmonary fibrosis and one who received two bone marrow transplants for acute lymphocytic leukemia and subsequently developed chemotherapy-induced pulmonary fibrosis).

MEASUREMENTS

Pulmonary function testing, exercise oximetry, quantitative ventilation-perfusion lung scanning. Actuarial survival.

RESULTS

All patients had marked improvement in pulmonary function, exercise oximetry, and quantitative ventilation perfusion to the SLT. One patient with scleroderma died 90 days postoperatively from Pseudomonas pneumonia with a sepsis syndrome. One patient with sarcoidosis died 150 days postoperatively from disseminated aspergillosis. At autopsy, there was no evidence of recurrent fibrosis or sarcoidosis in the transplanted lungs in either of these two patients. The seven surviving patients have returned to work or school and are conducting all activities of daily living without pulmonary disability. The 1- and 2-year actuarial survival rates in these nine patients is 68.6 percent as compared with the 1- and 2-year actuarial survival rates of 66.3 percent and 55.8 percent in the remainder of our SLT group as a whole (n = 49). Despite pharmacologic immunosuppression, there is no evidence of recurrent malignancy in the 3 patients with prior malignancies.

CONCLUSIONS

We conclude that carefully selected patients with end-stage lung involvement related to systemic disease or chemotherapy-induced fibrosis may benefit from SLT.

Lung transplantation

Solid-organ transplantation has flourished during the last decade, with transplantation of heart and lungs becoming available to patients with end-stage cardiac or pulmonary diseases. The first lung transplant was performed in 1963 on a 58-year-old man with bronchogenic carcinoma. He survived for 18 days. During the next two decades, approximately 40 lung transplant procedures were attempted without success. These early attempts at lung transplantation were unsuccessful because of the development of lung rejection, anastomotic complications, or infection in the transplant recipients. In the early 1980s, human heart-lung transplantation was successfully performed for the treatment of pulmonary vascular disease. After this procedure, single-lung transplantation for the treatment of end-stage interstitial lung disease and obstructive lung disease was developed. More recently, the technique of double-lung transplantation has come into existence. This article reviews various aspects of lung transplantation, including immunosuppression, lung graft preservation, the various surgical techniques and types of lung transplant procedures available, recipient and donor selection criteria, and postoperative care of the transplant recipient. In addition, infectious and noninfectious complications seen in this particular patient population, including acute and chronic rejection, will be discussed.

Early bacterial infections in lung transplant recipients

Early bacterial pulmonary infections within 2 weeks after lung transplantation were studied in 29 patients undergoing surgery between December 1989 and May 1992. Suspected pulmonary infections occurred in 11 patients (38 percent). The most common bacterial organisms isolated were Klebsiella pneumoniae (45 percent; 5/11), Pseudomonas aeruginosa (36 percent; 4/11), Escherichia coli (27 percent; 3/11), Staphylococcus aureus (18 percent; 2/11), and Enterobacter cloacae (18 percent; 2/11). The mortality due to infection was 3 percent (1/29) in the early postoperative period. None of the following variables was found to be of prognostic significance: positive donor cultures, ischemic time of the graft, use of cardiopulmonary bypass, number of courses of methylprednisolone for acute rejection, duration of postoperative intubation, and type of surgical procedure. The presence of infection in the early postoperative period did not influence long-term survival. In the absence of prognostic parameters, prompt adjustment of antibiotic therapy to the results of antibiograms remains the most important therapeutic step in the management of infections in the early postoperative period after lung transplantation.

Prostacyclin (epoprostenol) and heart-lung transplantation as treatments for severe pulmonary hypertension

OBJECTIVE

To determine whether epoprostenol (prostacyclin, PGI2) or heart-lung transplantation (HLT), or both improves survival of patients with severe pulmonary hypertension.

DESIGN

This was a prospective study where the effects of epoprostenol were compared with conventional treatment. Also, the benefits of epoprostenol and HLT were assessed by comparing survival in this group with that of 120 patients at the Mayo Clinic before HLT and epoprostenol treatment became available.

PATIENTS AND INTERVENTIONS

Forty four patients were studied; 25 received continuous epoprostenol over a four year period (mean (SD) cardiac index 1.8 (0.4) 1 min-1 m-2 and mean (SD) pulmonary artery pressure (PAP) 70 (16) mm Hg) and 19 did not (cardiac index 2.1 (0.6) 1 min-1 m-2 and PAP 64 (13) mm Hg). Ten patients underwent HLT: seven had received epoprostenol, and three had not.

RESULTS

The therapeutic intervention with epoprostenol, or HLT, or both improved survival compared with the Mayo clinic patients (p = 0.05). Most of the benefit was conferred by epoprostenol, which prolonged survival twofold from a median time of eight to 17 months and doubled the changes of successful HLT. The improved survival with epoprostenol was not related to its immediate capacity to cause pulmonary vasodilation. Those patients who had limited acute pulmonary vasodilation when treated with epoprostenol showed the greatest improvement in survival.

CONCLUSIONS

These preliminary results indicate that those pulmonary hypertensive patients with the poorest chance of survival can be helped by epoprostenol and by HLT.

Echocardiographic characterization of the improvement in right ventricular function in patients with severe pulmonary hypertension after single-lung transplantation

OBJECTIVES

This study was designed to characterize immediate, early and long-term changes in right ventricular structure and function, as defined by two-dimensional and Doppler echocardiography, after single-lung transplantation in patients with severe pulmonary hypertension.

BACKGROUND

Single-lung transplantation has recently been shown to dramatically improve hemodynamics in patients with primary pulmonary hypertension who had unsuccessful medical therapy.

METHODS

Fourteen patients with severe pulmonary hypertension who underwent single-lung transplantation were studied with transthoracic and transesophageal two-dimensional and Doppler echocardiography. Right ventricular dimensions were measured in the apical four-chamber view. Right ventricular ejection and acceleration times and peak velocity of tricuspid regurgitation were measured by Doppler study. Results of right heart catheterization were available early (< 3 months) after transplantation in 10 of 13 patients and late after transplantation (6 months to 2 years) in 11 patients.

RESULTS

In the early posttransplantation studies, right ventricular dimensions decreased and fractional area change and ejection fraction increased in all patients, but right ventricular wall thickness did not change significantly. Tricuspid regurgitation lessened markedly in all patients. Long-term decreases in right ventricular dimension and improvement in systolic function were sustained. Right ventricular wall thickness significantly decreased compared with the early postoperative value (0.76 +/- 0.1 cm compared with 0.63 +/- 0.14 cm, p < 0.02).

CONCLUSIONS

Two-dimensional echocardiography demonstrates sustained improvement in right ventricular function after single-lung transplantation for severe pulmonary hypertension despite severe preoperative dysfunction.