Jonathan B. Orens

Dysfunctional Voltage-Gated K+ Channels in Pulmonary Artery Smooth Muscle Cells of Patients With Primary Pulmonary Hypertension

BACKGROUND Primary pulmonary hypertension (PPH) is a rare disease of unknown cause. Although PPH and secondary pulmonary hypertension (SPH) share many clinical and pathological characteristics, their origins may be disparate. In pulmonary artery smooth muscle cells (PASMCs), the activity of voltage-gated K+ (KV) channels governs membrane potential (Em) and regulates cytosolic free Ca2+ concentration ([Ca2+]cyt). A rise in [Ca2+]cyt is a trigger of vasoconstriction and a stimulus of smooth muscle proliferation. METHODS AND RESULTS Fluorescence microscopy and patch clamp techniques were used to measure [Ca2+]cyt, Em, and KV currents in PASMCs. Mean pulmonary arterial pressures were comparable (46+/-4 and 53+/-4 mm Hg; P=0.30) in SPH and PPH patients. However, PPH-PASMCs had a higher resting [Ca2+]cyt than cells from patients with SPH and nonpulmonary hypertension disease. Consistently, PPH-PASMCs had a more depolarized Em than SPH-PASMCs. Furthermore, KV currents were significantly diminished in PPH-PASMCs. Because of the dysfunctional KV channels, the response of [Ca2+]cyt to the KV channel blocker 4-aminopyridine was significantly attenuated in PPH-PASMCs, whereas the response to 60 mmol/L K+ was comparable to that in SPH-PASMCs. CONCLUSIONS These results indicate that KV channel function in PPH-PASMCs is inhibited compared with SPH-PASMCs. The resulting membrane depolarization and increase in [Ca2+]cyt lead to pulmonary vasoconstriction and PASMC proliferation. Our data suggest that defects in PASMC KV channels in PPH patients may be a unique mechanism involved in initiating and maintaining pulmonary vasoconstriction and appear to play a role in the pathogenesis of PPH.

A review of lung transplant donor acceptability criteria

Abstract (A consensus report from The Pulmonary Council of the International Society for Heart and Lung Transplantation)

Impaired β-adrenergic receptor stimulation of cyclic adenosine monophosphate in human septic shock : association with myocardial hyporesponsiveness to catecholamines

ObjectivesTo determine whether myocardial hyporesponsiveness to administered catecholamines occurs in human sepsis and whether this phenomenon is associated with impaired β-adrenergic receptor stimulation of cyclic adenosine monophosphate. DesignProspective study. SettingMedical ICU in a university hospital. PatientsNormal human volunteers (n = 7), critically ill patients who were not septic (n = 9), septic patients not in shock (n = 16), and septic patients in shock (n = 17). Measurements and Main ResultsPulmonary artery catheter-derived hemodynamic data were obtained in patients with sepsis and septic shock. Isoproterenol and sodium fluoride-stimulated cyclic adenosine monophosphate accumulations were measured in circulating lymphocytes. The hemodynamic response to sequential infusions of dobutamine, 5 and 10 μg/ kg/min, was obtained in septic and septic shock patients. Baseline hemodynamic values for mean arterial pressure, cardiac index, left ventricular stroke work index, and oxygen delivery index at approximately 2 days after the onset of sepsis were significantly lower in septic shock patients compared with septic (nonshock) patients (p < .01, p < .05, p < .001, p < .01, respectively). Isoproterenol-and sodium fluoride-stimulated cyclic adenosine monophosphate accumulations were significantly reduced in septic shock patients compared with those accumulations observed in septic patients (p < .01 and p < .001, respectively). The heart rate response to 10 μg/ kg/min of dobutamine was significantly (p < .01) lower in septic shock patients compared with septic patients. ConclusionsIn patients with septic shock, impaired β-adrenergic receptor stimulation of cyclic adenosine monophosphate is associated with myocardial hyporesponsiveness to catecholamines, suggesting that β-adrenergic receptor dysfunction may contribute to the reduced myocardial performance observed in this shock state. (Crit Care Med 1993; 21:31–39)

An international ISHLT/ATS/ERS clinical practice guideline: diagnosis and management of bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is a major complication of lung transplantation that is associated with poor survival. The International Society for Heart and Lung Transplantation, American Thoracic Society, and European Respiratory Society convened a committee of international experts to describe and/or provide recommendations for 1) the definition of BOS, 2) the risk factors for developing BOS, 3) the diagnosis of BOS, and 4) the management and prevention of BOS. A pragmatic evidence synthesis was performed to identify all unique citations related to BOS published from 1980 through to March, 2013. The expert committee discussed the available research evidence upon which the updated definition of BOS, identified risk factors and recommendations are based. The committee followed the GRADE (Grading of Recommendation, Assessment, Development and Evaluation) approach to develop specific clinical recommendations. The term BOS should be used to describe a delayed allograft dysfunction with persistent decline in forced expiratory volume in 1 s that is not caused by other known and potentially reversible causes of post-transplant loss of lung function. The committee formulated specific recommendations about the use of systemic corticosteroids, cyclosporine, tacrolimus, azithromycin and about re-transplantation in patients with suspected and confirmed BOS. The diagnosis of BOS requires the careful exclusion of other post-transplant complications that can cause delayed lung allograft dysfunction, and several risk factors have been identified that have a significant association with the onset of BOS. Currently available therapies have not been proven to result in significant benefit in the prevention or treatment of BOS. Adequately designed and executed randomised controlled trials that properly measure and report all patient-important outcomes are needed to identify optimal therapies for established BOS and effective strategies for its prevention. Diagnosis of BOS requires careful exclusion of other complications that can cause delayed lung allograft dysfunction http://ow.ly/AZmbr

PDE5A Inhibitor Treatment of Persistent Pulmonary Hypertension After Mechanical Circulatory Support

Background—Pulmonary hypertension (PH) secondary to left heart failure portends a poor prognosis and is a relative contraindication to heart transplantation at many centers. We tested the hypothesis that when PH persists after adequate left ventricle unloading via recent left ventricular assist device (LVAD) therapy, phosphodiesterase type 5A inhibition would decrease PH in this population. Methods and Results—We performed an open-label clinical trial using control patients not receiving therapy. Between 1999 and 2007, 138 consecutive patients undergoing cardiac transplantation evaluation with advanced left ventricular dysfunction, an elevated pulmonary capillary wedge pressure, and PH (defined by a pulmonary vascular resistance (PVR) >3 Woods Units), were treated with LVAD therapy. Fifty-eight of these patients reduced their pulmonary capillary wedge pressure to a value <15 mm Hg (11.8±2.0 mm Hg from baseline 23.2±6.2 mm Hg) 1 to 2 weeks after LVAD implantation, but despite this improvement, the PVR of these patients was only minimally affected (5.65±3.00 to 5.39±1.78 Wood Units). Twenty-six consecutive patients from this group with persistently elevated PVR were started on oral phosphodiesterase type 5A inhibition with sildenafil and titrated to an average of dose of 51.9 mg by mouth 3 times per day. The average PVR in the sildenafil-treated group fell from 5.87±1.93 to 2.96±0.92 Wood Units (P<0.001) and the mean pulmonary artery pressure fell from 36.5±8.6 to 24.3±3.6 mm Hg (P<0.0001) and was significantly lower when compared with the 32 LVAD recipients not receiving sildenafil at weeks 12 to 15 after the initial post-LVAD hemodynamic measurements (13 to 17 weeks post-LVAD implantation). In addition, hemodynamic measurements of right ventricular function in sildenafil-treated patients was also improved compared with patients not receiving sildenafil. Conclusions—In patients with persistent PH after recent LVAD placement, phosphodiesterase type 5A inhibition in this open-label trial resulted in a significant decrease in PVR when compared with control patients.

Patterns and Significance of Exhaled-Breath Biomarkers in Lung Transplant Recipients with Acute Allograft Rejection

BACKGROUND Obliterative bronchiolitis (OB) remains one of the leading causes of death in lung transplant recipients after 2 years, and acute rejection (AR) of lung allograft is a major risk factor for OB. Treatment of AR may reduce the incidence of OB, although diagnosis of AR often requires bronchoscopic lung biopsy. In this study, we evaluated the utility of exhaled-breath biomarkers for the non-invasive diagnosis of AR. METHODS We obtained breath samples from 44 consecutive lung transplant recipients who attended ambulatory follow-up visits for the Johns Hopkins Lung Transplant Program. Bronchoscopy within 7 days of their breath samples showed histopathology in 21 of these patients, and we included them in our analysis. We measured hydrocarbon markers of pro-oxidant events (ethane and 1-pentane), isoprene, acetone, and sulfur-containing compounds (hydrogen sulfide and carbonyl sulfide) in exhaled breath and compared their levels to the lung histopathology, graded as stable (non-rejection) or AR. None of the study subjects were diagnosed with OB or infection at the time of the clinical bronchoscopy. RESULTS We found no significant difference in exhaled levels of hydrocarbons, acetone, or hydrogen sulfide between the stable and AR groups. However, we did find significant increase in exhaled carbonyl sulfide (COS) levels in AR subjects compared with stable subjects. We also observed a trend in 7 of 8 patients who had serial sets of breath and histopathology data that supported a role for COS as a breath biomarker of AR. CONCLUSIONS This study demonstrated elevations in exhaled COS levels in subjects with AR compared with stable subjects, suggesting a diagnostic role for this non-invasive biomarker. Further exploration of breath analysis in lung transplant recipients is warranted to complement fiberoptic bronchoscopy and obviate the need for this procedure in some patients.

Induction therapy in lung transplantation: a prospective, controlled clinical trial comparing OKT3, anti-thymocyte globulin, and daclizumab

BACKGROUND Because acute rejection is associated with inferior outcomes in lung transplantation, we have routinely employed OKT3, anti-thymocyte globulin (ATG), or daclizumab as adjuncts to reduce rejection. METHOD We performed a 4-year prospective, controlled clinical trial of these 3 therapies to determine differences in post-operative infection, rejection, survival, and bronchiolitis obliterans syndrome (BOS). Eighty-seven consecutive lung transplant patients received OKT3 (n = 30), ATG (n = 34), and daclizumab (n = 23) as induction agents. The groups had similar demographics and immunosuppression protocols differing only in induction agents used. RESULTS No differences were observed in immediate post-operative outcomes such as length of hospitalization, ICU stay, or time on ventilators. Twelve months post-transplant, OKT3 had more infections per patient than the other agents, a difference that only became significant 2 months post-operatively (p = 0.009). The most common infection was bacterial and OKT3 had more bacterial infections than any other agent. Daclizumab had more patients remain infection free in the first year (p = 0.02), having no fungal infections and a low rate of viral infections. No patient receiving daclizumab developed drug specific side-effects. Only those patients with episodes of acute rejection developed BOS. There were no significant differences in the freedom from acute rejection or BOS between the groups. The 2-year survival for the entire cohort was 68%, with no differences observed in patient survival. CONCLUSIONS This study again reveals the importance of acute rejection in the subsequent development of BOS. Although daclizumab offers a low risk of post-transplant infection and drug specific side-effects, no drug is superior in delaying rejection or BOS or in prolonging long-term survival.

Impact of U.S. Lung Allocation Score on Survival After Lung Transplantation

BACKGROUND The Lung Allocation Score (LAS) dramatically changed organ allocation in lung transplantation. The impact of this change on patient outcomes is unknown. The purpose of the study was to examine early mortality after lung transplantation under the LAS system. METHODS All patients undergoing first-time lung transplantation during the period from May 1, 2005 through April 30, 2008 were included in the study. The cohort was divided into quintiles by LAS. A high-risk group (LAS >46) was comprised of the highest quintile, Quintile 5, and a low-risk group (LAS < or =46) included the lower quintiles, Quintiles 1 through 4. A time-to-event analysis was performed for risk of death after transplantation using Kaplan-Meier survival and Cox proportional hazards models. RESULTS There were 4,346 patients who underwent lung transplantation during the study period. Patients in the high-risk group (LAS >46) were more likely to have idiopathic pulmonary fibrosis (IPF; 52.9% vs 23.8%, p < 0.001) and diabetes (25.8% vs 16.8%, p < 0.001) and to require mechanical ventilatory support (15.4% vs 2.2%, p < 0.001) at the time of transplant as compared with patients in the low-risk group. One-year survival using the Kaplan-Meier product limit estimator was significantly worse in the high-risk group (75% vs 83%, p < 0.001 by log-rank test). Patients in the high-risk group were also found to have increased risk of death (hazard ratio 1.46, 95% confidence interval 1.24 to 1.73) compared with the low-risk group. CONCLUSIONS Overall 1-year survival under the new LAS system appears to be similar to that in historic reports. However, risk of death was significantly increased among patients with LAS >46.

Obesity and Primary Graft Dysfunction after Lung Transplantation: The Lung Transplant Outcomes Group Obesity Study

RATIONALE Obesity has been linked to acute lung injury and is a risk factor for early mortality after lung transplantation. OBJECTIVES To examine the associations of obesity and plasma adipokines with the risk of primary graft dysfunction after lung transplantation. METHODS We performed a prospective cohort study of 512 adult lung transplant recipients with chronic obstructive pulmonary disease or interstitial lung disease enrolled in the Lung Transplant Outcomes Group Study. In a nested case-control study, we measured plasma leptin, adiponectin, and resistin before lung transplantation and 6 and 24 hours after lung transplantation in 40 cases of primary graft dysfunction and 80 control subjects. Generalized linear mixed models and logistic regression were used to estimate risk ratios and odds ratios. MEASUREMENTS AND MAIN RESULTS Grade 3 primary graft dysfunction developed within 72 hours of transplantation in 29% participants. Obesity was associated with a twofold increased risk of primary graft dysfunction (adjusted risk ratio 2.1; 95% confidence interval, 1.7-2.6). The risk of primary graft dysfunction increased by 40% (confidence interval, 30–50%) for each 5 kg/m(2) increase in body mass index after accounting for center, diagnosis, cardiopulmonary bypass, and transplant procedure. Higher plasma leptin levels were associated with a greater risk of primary graft dysfunction (sex-adjusted P = 0.02). The associations of both obesity and leptin with primary graft dysfunction tended to be stronger among those who did not undergo cardiopulmonary bypass. CONCLUSIONS Obesity is an independent risk factor for primary graft dysfunction after lung transplantation.

Construct validity of the definition of primary graft dysfunction after lung transplantation

BACKGROUND This study tested the discriminant validity of International Society for Heart and Lung Transplantation (ISHLT) primary graft dysfunction (PGD) grades with lung injury biomarker profiles and survival. METHODS The study samples consisted of a multicenter prospective cohort study for the biomarker analysis and a cohort study of 450 patients for the mortality analyses. PGD was defined according to ISHLT consensus at 24, 48, and 72 hours after transplantation. We compared the changes in plasma markers of acute lung injury between PGD grades using longitudinal data models. To test predictive validity, we compared differences in the 30-day mortality and long-term survival according to PGD grade. RESULTS PGD Grade 3 demonstrated greater differences between plasma intercellular adhesion molecule 1 (ICAM-1), protein C, and plasminogen activator inhibitor type 1 (PAI-1) levels than did PGD Grades 0 to 2 at 24, 48, and 72 hours after lung transplantation (p < 0.05 for each). Grade 3 had the highest 30-day (test for trend p < 0.001) and overall mortality (log rank p < 0.001), with PGD Grades 1 and 2 demonstrating intermediate risks of mortality. The ability to discriminate both 30-day and overall mortality improved as the time of grading moved away from the time of transplantation (test for trend p < 0.001). CONCLUSIONS The ISHLT grading system has good discriminant validity, based on plasma markers of lung injury and mortality. Grade 3 PGD was associated with the most severely altered plasma biomarker profile and the worst outcomes, regardless of the time point of grading. PGD grade at 48 and 72 hours discriminated mortality better than PGD grade at 24 hours.