Should All Patients With Pulmonary Hypertension Undergoing Non-Cardiac Surgery Be Managed by Cardiothoracic Fellowship-Trained Anesthesiologists?

OBJECTIVES: To identify differences in practice patterns and outcomes related to the induction of general anesthesia for patients with pulmonary hypertension (PH) performed by anesthesiologists who have completed a cardiothoracic fellowship (CTA group) vs those who have not (non-CTA group). DESIGN: Retrospective study with propensity score matching. SETTING: Operating room. PARTICIPANTS: All adult patients with PH undergoing general anesthesia requiring intubation at a single academic center over 5 years. INTERVENTIONS: Patient baseline characteristics, peri-induction management variables, post-induction mean arterial pressure (MAP), and other outcomes were compared between CTA and non-CTA groups. METHODS AND MAIN RESULTS: Following propensity scoring matching, 402 patients were included in the final model, 100 in the CTA group and 302 in the non-CTA group. Also following matching, only cases of mild to moderate PH without right ventricular dysfunction remained in the analysis. Matched groups were overall statistically similar with respect to baseline characteristics; however, there was a greater incidence of higher ASA class (P = .025) and cardiology and thoracic procedures (P < .001) being managed by the CTA group. No statistical differences were identified in practice patterns or outcomes related to the induction of anesthesia between groups, except for longer hospital length of stay in the CTA group (P = .008). CONCLUSIONS: These results provide early evidence to suggest the induction of general anesthesia of patients with non-severe PH disease can be comparably managed by either anesthesiologists with or without a cardiothoracic fellowship. However, these findings should be confirmed in a prospective study.

Surgical Repair of Truncus Arteriosus: A Long-Term Hemodynamic Assessment.

Background: Unrepaired truncus arteriosus (TA) carries poor prognosis due to complications of unrestricted pulmonary flow, truncal valve insufficiency, and pulmonary vascular disease. Currently, the hemodynamic profile of adults late after TA repair is unknown. We reviewed the hemodynamics, prevalence, and pathophysiology of pulmonary hypertension (PH) in this population. Methods: Eighteen adult patients with repaired TA who underwent cardiac catheterization at Mayo Clinic, MN, between 1997 and 2021 were identified. PH was defined as either precapillary (mean pulmonary artery pressure [mPAP] ≥25 mm Hg, pulmonary artery wedge pressure [PAWP] ≤15 mm Hg, and pulmonary vascular resistance [PVR] >3 Wood units), isolated postcapillary (mPAP ≥25, PAWP >15, PVR ≤3), or combined (mPAP ≥25, PAWP >15, and PVR >3). Diastolic pressure and transpulmonary gradients were used as ancillary data for classification. Results: Mean age at catheterization was 34 ± 10 years. Mean right ventricular (RV) systolic pressure was 82 ± 22.6 mm Hg, mean right and left mPAPs 28.1 ± 16.2 and 27.9 ± 11.9 mm Hg, respectively. Seven patients (41.2%) had PAWP >15 mm Hg and, among those undergoing arterial catheterization, 7 (53.8%) had a left ventricular (LV) end-diastolic pressure >15 mm Hg. PH was diagnosed in 13 patients (72.2%): 6 (33.3%) precapillary, 4 (22.2%) isolated postcapillary, and 3 (16.7%) combined. PAWP >15 mm Hg was associated with male sex (P = .049),

Proposition of quantitative parameters for pre- and early post-operative assessment in pulmonary thromboendarterectomy - An Indian prospective study.

INTRODUCTION: Chronic thromboembolic pulmonary hypertension results from the incomplete resolution of the vascular obstruction associated with pulmonary embolism. Symptoms are exertional dyspnoea and fatigue, and over a period of time, right ventricular dysfunction sets in. Pulmonary thromboendarterectomy is an effective surgical remedy for this condition. Our study is an initial post-operative experience of pulmonary thromboendarterectomy and we have also tried to formulate quantitative parameters for the prediction of the post-operative course in patients who are undergoing surgery. METHODS: Twenty patients with chronic thromboembolic pulmonary hypertension underwent pulmonary thromboendarterectomy between July 2017 and January 2020. Pre-operatively, each patient was subjected to the (i) 6-min walk test, (ii) pre-operative brain natriuretic peptide values and (iii) pulmonary artery systolic pressure. Following the surgery and subsequent discharge, the patients were followed up at intervals of 15 days, 1, 3, 6, 9 months and at 1 year. At one year post-operatively, the same three quantitative tests were performed on each subject. RESULTS: Post-operatively, the mean 6-min walk distance was 499.75 m as against 341.35 m pre-operatively (p < 0.0001). Mean brain natriuretic peptide was 8.69 pm/l as against 47.58 pm/l pre-operatively (p < 0.0001). Mean pulmonary artery systolic pressure was 22.25 as against 67.1 pre-operatively (p < 0.0001). CONCLUSION: 6-Min walk test, brain natriuretic peptide and pulmonary artery systolic pressure could be considered as useful predictors of the haemodynamic severity of disease and predict the post-operative outcome.

Serial right heart catheter assessment between balloon pulmonary angioplasty sessions identify procedural factors that influence response to treatment.

BACKGROUND: Balloon pulmonary angioplasty (BPA) is delivered as a series of treatments for patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH) however, there is little published data on the procedural determinants of outcome. METHODS: Pre- and post-BPA clinical and hemodynamic data, as well as serial hemodynamic and procedural data at each BPA session were evaluated to determine patient and procedure-related factors that influence hemodynamic response. RESULTS: Per procedure data from 210 procedures in 84 patients and per patient data from 182 procedures in 63 patients with completed treatment and 3-month follow-up were analyzed. A median of 3 (range 1-6) BPA procedures treating a median of 2 segments per procedure (range 1-3) were performed per patient with a median interval between procedures of 42 (range 5-491) days. Clinical outcome correlated with hemodynamic change (pulmonary vascular resistance [ΔPVR] vs Cambridge Pulmonary Hypertension Outcome Review [CAMPHOR] symptom score: p < 0.001, Pearson's r = 0.48, n = 49). Responders to BPA had more severe disease at baseline and 37.5 % of non-responders were post-PEA. There was a dose-response relationship between per procedure and total number of segments treated and hemodynamic improvement (ΔPVR: 1 segment: -0.9%, 2: -14.5%, 3 or more: -16.1%, p < 0.001). Treating totally occluded vessels had a greater hemodynamic effect (mean pulmonary artery pressure [ΔmPAP]: sessions with occlusion: -8.0%, without occlusion treated: -3.2%, p < 0.05) without an increased complication rate. CONCLUSIONS: The magnitude of clinical benefit is related to the hemodynamic effect of BPA which in turn is related to the number of segments treated and lesion severity. Patients who were post-PEA were less likely to respond to BPA.

Postoperative Inhaled Nitric Oxide Does Not Decrease Length of Stay in Pediatric Cardiac Surgery Admissions.

Pulmonary hypertension is one of the most challenging complications in congenital heart surgery. The purpose of this study was to characterize inhaled nitric oxide administration in children with and without pulmonary hypertension who underwent congenital heart surgery and to describe the effect of nitric oxide administration on admission outcomes. This is a cross-sectional study utilizing data from the Pediatric Health Information System (PHIS) and PHIS + databases from 2004 to 2015. Pediatric patients with a congenital heart disease diagnosis were included and divided into groups with pulmonary hypertension that received and not received inhaled nitric oxide and patients without diagnosis of pulmonary hypertension who received and did not receive inhaled nitric oxide. For all admissions, the following were captured: age of admission, gender, year of admission, length of stay, billed charges, inpatient mortality, the presence of specific congenital malformations of the heart, specific cardiac surgeries, and comorbidities. Comparisons between groups were completed using a Mann-Whitney-U test and Fisher's exact test. Outcomes evaluation was completed using univariate and regression analyses. A total of 40,194 pediatric cardiac surgical admissions without pulmonary hypertension were identified. Of these, 726 (1.8%) received inhaled nitric oxide. Regression analyses demonstrated that inhaled nitric oxide was independently associated with increased length of stay, billed charges, and inpatient mortality. A total of 1678 pediatric cardiac surgical admissions with pulmonary hypertension were identified. Of these, 195 (11.6%) received inhaled nitric oxide. Regression analyses demonstrated that inhaled nitric oxide was independently associated with a significant increase in length of stay and billed charges. There was no statistically significant association between inhaled nitric oxide and decrease mortality. Administration of inhaled nitric oxide after pediatric cardiac surgery increases length of stay and billed charges while not providing improved inpatient mortality. In fact, administration of inhaled nitric oxide was associated with increased mortality in those without pulmonary hypertension while not impacting mortality in any way in those with pulmonary hypertension.

Pulmonary hypertension in patients with a subaortic right ventricle: prevalence, impact and management.

OBJECTIVE: This study sought to determine the prevalence, predictors, prognostic relevance and evolution of pulmonary hypertension (PH) (mean pulmonary artery pressure ≥25 mm Hg) in adult patients with a subaortic right ventricle (RV) in a biventricular circulation (2V-RV). METHODS: We analysed retrospective data from patients with 2V-RV undergoing cardiac catheterisation in our centre between 2000 and 2018. Echocardiographic assessment of subpulmonary ventricular pressures (left ventricular systolic pressure (LVSP)), age and B-type natriuretic peptide (BNP) were assessed as PH screening tools. Kaplan-Meier curves examined time to a composite outcome of death, transplant or ventricular assist device (VAD). Data from repeat catheterisations were analysed to evaluate PH changes over time, including the effects of therapy. RESULTS: A total of 141 patients (median age 39 (IQR 33-45) years, 68% men) underwent 191 cardiac catheterisations. At baseline, 55% had PH (isolated postcapillary 24%, combined precapillary and postcapillary 26% and precapillary 5%). BNP (area under the curve 0.80; 95% CI 0.72 to 0.88; p<0.0001), but not age at catheterisation or echocardiographic estimates of LVSP were associated with the presence of PH. The absence of PH and BNP <100 pg/mL discriminated a subgroup at very low risk during short-term (2.5 (1.3-3.9) years) follow-up (p<0.0001). Diuretics, milrinone and VAD improved haemodynamics over time. CONCLUSION: PH is prevalent in patients with 2V-RV even when asymptomatic. It is difficult to identify by echocardiography and most importantly, is strongly associated with adverse outcomes. PH affects prognosis and transplant options for this patient group and yet is often amenable to treatment. Awareness of these results ought to lower the threshold for invasive haemodynamic assessment and may change the management of failing patients with 2V-RV.

Effectiveness, safety, and Economic Comparison of Two Inhaled Epoprostentol Products (Flolan and Veletri) in Cardiothoracic Surgery Patients.

BACKGROUND: No previous studies exist examining two inhaled epoprosternol formulations (Flolan compared with Veletri) in a homogenous cardiothoracic surgery patient population. OBJECTIVE: To compare the impact of inhaled Flolan and inhaled Veletri on the effectiveness, safety, or cost in cardiothoracic surgery patients. MATERIALS AND METHODS: This was a retrospective, noninferiority study comparing inhaled Flolan and inhaled Veletri in cardiothoracic surgery patients. Participants included were ≥18 years old, admitted to the cardiothoracic intensive care unit, and received inhaled Flolan or inhaled Veletri therapy for ≥1 hour. RESULTS: A total of 244 patients were included in the primary outcome analysis (122 patients per group). The primary outcome, change in the partial pressure of arterial oxygen to fraction of inspired oxygen (PaO2/FiO2) ratio 1 hour after administration of inhaled Flolan or inhaled Veletri, did not cross the lower limit of the noninferiority margin (95% CI = -14.8 to 65.4). Significant differences in secondary outcomes included duration of mechanical ventilation (4.4 vs 2.6 days; P < 0.01), number of tracheostomies (24 vs 9; P = 0.01), number of patients initiated on dialysis (25 vs 12; P = 0.02), and cost per median duration of therapy ($257 vs $183; P = 0.02) in the inhaled Flolan and inhaled Veletri groups, with the average duration of therapy being 1.6 and 1.3 days, respectively. CONCLUSIONS AND RELEVANCE: Inhaled Veletri was demonstrated to be non-inferior to inhaled Flolan when comparing change in PaO2/FiO2 ratio 1 hour post -therapy initiation,and inhaled Veletri was an acceptable alternative to inhaled Flolan in a cardiothoracic surgery patient population.

Transesophageal Echocardiographic Assessment of Pulmonary Artery-to-Ascending Aorta Ratio for the Detection of Pulmonary Hypertension in Cardiac Surgical Patients.

OBJECTIVE: The objective of the study was to investigate if the main pulmonary artery (mPA)-to-ascending aorta (AscAo), (mPA:AscAo) ratio could serve as a screening tool in identifying pulmonary artery hypertension (PAH). DESIGN: A prospective observational study. SETTING: Tertiary care center, university hospital. PARTICIPANTS: Fifty-four adult patients undergoing off-pump coronary artery bypass grafting surgery (OPCAB). INTERVENTIONS: mPA and AscAo transverse diameters were measured by transesophageal echocardiography (TEE) and the mean pulmonary arterial pressures (mPAP) were recorded simultaneously using a pulmonary artery catheter. MEASUREMENTS AND MAIN RESULTS: mPA:AscAo ratio demonstrated significant linear correlation with mPAP measured by pulmonary artery catheterization (ie, r = 0.61, confidence interval [CI] = 0.5352-0.6736, p < 0.0001). Receiver operating characteristic curves were performed to evaluate sensitivity and specificity of mPA:AscAo ratio ≥1 for diagnosing PAH (mPAP ≥25 mmHg). Area under the curve for mPA:AscAo ratio was 0.91 (95% CI, 0.869-0.936, p < 0.0001), with a sensitivity of 84.27%, specificity of 83.92%, positive-predictive value of 87.6% and negative-predictive value of 81.1% for a mPAP ≥25 mmHg. CONCLUSIONS: The ratio of mPA:AscAo is a simple, reliable, and reproducible method that can be obtained through TEE, which guides the clinician to screen patients with PAH.

Operability assessment in CTEPH: Lessons from the CHEST-1 study.

Pulmonary endarterectomy is the gold standard treatment for chronic thromboembolic pulmonary hypertension and is potentially curative, although some patients are unsuitable for pulmonary endarterectomy and require alternative management. Lack of standardized assessment of pulmonary endarterectomy eligibility risks suboptimal treatment in some patients. We discuss the implications for future clinical trials and practice of a unique operability assessment in patients who have chronic thromboembolic pulmonary hypertension and were initially screened for inclusion in the CHEST-1 (Chronic Thromboembolic Pulmonary Hypertension Soluble Guanylate Cyclase Stimulator Trial-1) study. The CHEST-1 study evaluated riociguat for the treatment of inoperable chronic thromboembolic pulmonary hypertension (CTEPH) or persistent/recurrent pulmonary hypertension after pulmonary endarterectomy. Screened patients who were initially considered "inoperable" underwent central independent adjudication by a committee of experienced surgeons, or local adjudication in collaboration with an experienced surgeon. Operability decisions were based on accessibility of thrombi and the association between pulmonary vascular resistance (PVR) and the extent of obstruction, using pulmonary angiography/computed tomography with ventilation/perfusion scintigraphy as the minimum diagnostic tests. Of 446 patients screened for CHEST-1, a total of 188 and 124 underwent central and local adjudication, respectively, after being initially considered to be "inoperable." After a second assessment by an experienced surgeon, 69 of these 312 "inoperable" patients were deemed operable. Rigorous measures in CHEST-1 guaranteed that only technically inoperable patients, or patients who had persistent/recurrent pulmonary hypertension, were enrolled, thus ensuring that only patients for whom surgery was not an option were enrolled. This study design sets new standards for future clinical trials and practice in CTEPH, helping to ensure that patients who have CTEPH receive optimal treatment.

Assessment of right ventricular adaptability to loading conditions can improve the timing of listing to transplantation in patients with pulmonary arterial hypertension.

BACKGROUND: Right ventricle (RV) performance is load dependent, and right-sided heart failure (RHF) is the main cause of death in pulmonary arterial hypertension (PAH). Prediction of RV worsening for timely identification of patients needing transplantation (Tx) is paramount. Assessment of RV adaptability to load has proved useful in certain clinical circumstances. This study assessed its predictive value for RHF-free and Tx-free outcome with PAH. METHODS: Between 2006 and 2012, all potential Tx candidates with PAH, without RHF at the first evaluation, were selected for follow-up (except congenital heart diseases). At selection and at each follow-up, N-terminal prohormone brain natriuretic peptide (NT-proBNP) and the 6-minute walk distance were measured, and RV adaptability to load was assessed by echocardiography. Collected data were tested for the ability to predict RV stability and Tx-free survival. RESULTS: During a 12-month to 92-month follow-up, RHF developed in 23 of 79 evaluated patients, despite similar medication and no differences in initial RV size and ejection fraction compared with the patients who remained stable. However, unstable patients had an initially lower RV load-adaptation index and afterload-corrected peak global systolic longitudinal strain-rate values as well as higher RV dyssynchrony, tricuspid regurgitation, and NT-proBNP levels (p ≤ 0.01). At certain cutoff values, these variables appeared predictive for 1-year and 3-year freedom from RHF and 3-year Tx-free survival. An RV load-adaptation index reduction of ≥20% showed the highest predictive value (90.0%) for short-term (≤1 year) RV decompensation. CONCLUSIONS: Assessment of RV adaptability to load allows prediction of RV function and Tx-free survival with severe PAH during the next 1 to 3 years. This can improve the timing of listing for Tx.

Significance of echocardiographic assessment for right ventricular function after balloon pulmonary angioplasty in patients with chronic thromboembolic induced pulmonary hypertension.

Balloon pulmonary angioplasty (BPA) may improve hemodynamics and exercise tolerance in patients with chronic thromboembolic pulmonary hypertension (CTEPH). We studied consecutive 25 patients with CTEPH who underwent BPA and evaluated hemodynamics by right-sided heart catheterization. Right ventricular (RV) function was assessed before and after BPA by echocardiography including speckle-tracking echocardiography and 3-dimensional echocardiography. BPA improved the mean pulmonary artery pressure, pulmonary vascular resistance, and cardiac index. BPA also ameliorated the 3-dimentional RV volume, RV ejection fraction, and RV systolic peak strain, all of which were significantly correlated with hemodynamic parameters. The changes in cardiac index were significantly correlated with those in 3-dimentional RV volume index. Furthermore, RV dyssynchrony quantified by the RV strain analyses was ameliorated after BPA even in patients with mild pulmonary hypertension, implicating the merit of BPA in this patient population with CTEPH. BPA not only improved the hemodynamics in patients with CTEPH, but also ameliorated RV remodeling and dyssynchrony as assessed by 3-dimensional echocardiography or speckle-tracking echocardiography. Thus, the assessment of RV function may provide valuable information about the appropriate indication for BPA, its efficacy, and the therapeutic goal for patients with CTEPH.

Functional assessment and quality of life before and after pulmonary endoarterectomy.

PURPOSE: The study investigates Quality of Life (QOL) and correlation with functional status of patients affected by Chronic Thromboembolic Pulmonary Hypertension who undergo Pulmonary Endoarterectomy. METHODS: We investigated with an observational design (before surgery, three and twelve months afterwards) the hemodynamic data (NYHA class, mean pulmonary arterial pressure, cardiac output and pulmonary vascular resistance), the functional status (using the 6-Minute Walk Test) and the QOL, using three questionnaires: Medical Outcome Study Short Form-36 (SF-36), Minnesota Living with Heart Failure Questionnaire (MLHFQ), Saint George Respiratory Questionnaire (SGRQ). We report the results of forty-nine patients. RESULTS: After surgery there was an improvement on functional and hemodynamic parameters and on QOL. The physical domain (PCS) of SF-36 was weakly but significantly associated with all functional parameters. There was no association between functional parameters and mental domain (MCS) of SF-36 or SGRQ. The improvement in 6-Minute Walk Distance was associated with an increase in MLHFQ. CONCLUSIONS: Both QOL and submaximal exercise tolerance improve after surgery. However only the physical domains of SF-36 appear to be significantly associated to the functional data.

Assessment of left atrial volume before and after pulmonary thromboendarterectomy in chronic thromboembolic pulmonary hypertension.

BACKGROUND: Impaired left ventricular diastolic filling is common in chronic thromboembolic pulmonary hypertension (CTEPH), and recent studies support left ventricular underfilling as a cause. To investigate this further, we assessed left atrial volume index (LAVI) in patients with CTEPH before and after pulmonary thromboendarterectomy (PTE). METHODS: Forty-eight consecutive CTEPH patients had pre- & post-PTE echocardiograms and right heart catheterizations. Parameters included mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR), cardiac index, LAVI, & mitral E/A ratio. Echocardiograms were performed 6 ± 3 days pre-PTE and 10 ± 4 days post-PTE. Regression analyses compared pre- and post-PTE LAVI with other parameters. RESULTS: Pre-op LAVI (mean 19.0 ± 7 mL/m2) correlated significantly with pre-op PVR (R = -0.45, p = 0.001), mPAP (R = -0.28, p = 0.05) and cardiac index (R = 0.38, p = 0.006). Post-PTE, LAVI increased by 18% to 22.4 ± 7 mL/m2 (p = 0.003). This change correlated with change in PVR (765 to 311 dyne-s/cm5, p = 0.01), cardiac index (2.6 to 3.2 L/min/m2, p = 0.02), and E/A (.95 to 1.44, p = 0.002). CONCLUSION: In CTEPH, smaller LAVI is associated with lower cardiac output, higher mPAP, and higher PVR. LAVI increases by ~20% after PTE, and this change correlates with changes in PVR and mitral E/A. The rapid increase in LAVI supports the concept that left ventricular diastolic impairment and low E/A pre-PTE are due to left heart underfilling rather than inherent left ventricular diastolic dysfunction.

RV stroke work in children with pulmonary arterial hypertension: estimation based on invasive haemodynamic assessment and correlation with outcomes.

BACKGROUND: RV performance is an important determinant of outcomes in children with pulmonary arterial hypertension (PAH). RV stroke work (RVSW), the product of mean pulmonary artery pressure and stroke volume, integrates contractility, afterload and ventricular-vascular coupling. RVSW has not been evaluated in children with PAH. We tested the hypothesis that RVSW would be a predictor of outcomes in children with PAH. METHODS: Patients in the Children's Hospital Colorado PAH database were evaluated retrospectively, and those with idiopathic PAH and those with minor or repaired congenital heart disease were included. Haemodynamic data were obtained by catheterisation and echocardiography, performed within 3 months. RVSW was calculated: mean pulmonary arterial pressure × stroke volume, and indexed to body surface area. Statistics included Kruskal-Wallis, Wilcoxon rank sum, and Spearman correlation. RESULTS: Fifty patients were included. Median age of the cohort was 9.5 (6.0, 15.7) years, with a median indexed pulmonary vascular resistance (PVRi) of 6.5 (3.7, 11.6) WU m(2). RVSW had a significant association with PVRi (r=0.6, p<0.0001), tricuspid annular systolic plane excursion (r=0.55, p=0.0001), and RV fractional area change (r=-0.4, p=0.005). Grouped by WHO class, there was a significant difference in RVSW (p=0.04). Need for atrial septostomy and death were associated with higher RVSW (p=0.04 and p=0.03, respectively). CONCLUSIONS: RVSW can be estimated in children with PAH, and is significantly associated with abnormal WHO class, the need for septostomy, as well as mortality. Indices accounting for RV performance as well as ventricular-vascular coupling may be useful in the prognosis and, hence, management of children with PAH.

Biocompatibility Assessment of the CentriMag-Novalung Adult ECMO Circuit in a Model of Acute Pulmonary Hypertension.

Extracorporeal membrane oxygenation (ECMO) is rarely used in patients with severe pulmonary hypertension (PH) as a bridge to lung transplantation. In this study, we assess the blood biocompatibility of the integrated CentriMag-Novalung ECMO system (venoarterial) in an acute model of PH. Severe PH (≥2/3 systemic) was induced in eight sheep through progressive ligation of the main pulmonary artery. System performance, platelet activation, thromboelastography (TEG) parameters, fibrinogen, plasma-free hemoglobin, and total plasma protein were measured at initiation, 3, and 6 hr of support in the ECMO (N = 4) and sham (N = 4) groups. A stable ECMO flow (2.2 ± 0.1 L/min), low transmembrane pressure gradient, and steady blood O2 and CO2 levels were maintained. Platelet activation was low (<4%) in both the groups, whereas platelet responsiveness to agonist (platelet activating factor) was reduced in the sham group when compared with the ECMO group. There were no differences in the TEG parameters, fibrinogen concentration, plasma-free hemoglobin (<10 mg/dl), and plasma total protein between the two groups. The findings of low levels of platelet activation and plfHb suggest adequate blood biocompatibility of the integrated CentriMag-Novalung circuit use for short-term support in a model of PH.