Main Pulmonary Artery Pressure Research Articles

Dissecting contributions of pulmonary arterial remodeling to right ventricular afterload in pulmonary hypertension.

Pulmonary hypertension (PH) is defined as an elevation in the right ventricle (RV) afterload, characterized by increased hemodynamic pressure in the main pulmonary artery (PA). Elevations in RV afterload increase RV wall stress, resulting in RV remodeling and potentially RV failure. From a biomechanical standpoint, the primary drivers for RV afterload elevations include increases in pulmonary vascular resistance (PVR) in the distal vasculature and decreases in vessel compliance in the proximal PA. However, the individual contributions of the various vascular remodeling events toward the progression of PA pressure elevations and altered vascular hemodynamics remain elusive. In this study, we used a subject-specific one-dimensional (1D) fluid-structure interaction (FSI) model to investigate the alteration of pulmonary hemodynamics in PH and to quantify the contributions of vascular stiffening and increased resistance towards increased main pulmonary artery (MPA) pressure. We used a combination of subject-specific hemodynamic measurements, ex-vivo mechanical testing of arterial tissue specimens, and ex-vivo X-ray micro-tomography imaging to develop the 1D-FSI model and dissect the contribution of PA remodeling events towards alterations in the MPA pressure waveform. Both the amplitude and pulsatility of the MPA pressure waveform were analyzed. Our results indicated that increased distal resistance has the greatest effect on the increase in maximum MPA pressure, while increased stiffness caused significant elevations in the characteristic impedance. The method presented in this study will serve as an essential step toward understanding the complex interplay between PA remodeling events that leads to the most severe adverse effect on RV dysfunction.

A Personalized Pulmonary Circulation Model to Non-Invasively Calculate Fractional Flow Reserve for Artery Stenosis Detection

Fractional Flow Reserve (FFR) is regarded as a fundamental index to assess pulmonary artery stenosis. The application of FFR can increase the accuracy of detection of pulmonary artery stenosis. However, the invasive examination may carry a number of physiological risks for patients. Therefore, we propose a personalized pulmonary circulation model to non-invasively calculate FFR of pulmonary artery stenosis. We have employed a personalized pulmonary circulation model to non-invasively calculate FFR. This model combines boundary condition estimation and 3D pulmonary artery morphology reconstruction for CFD simulation. Firstly, we obtain patient-specific boundary conditions by matching cardiac output and main pulmonary artery pressure. Secondly, the 3D pulmonary artery morphology is reconstructed by semi-automatic segmentation. The CFD simulation is performed to obtain the pressure distribution in the entire pulmonary artery. Finally, the FFR in pulmonary artery stenosis is calculated as the ratio of distal pressure and proximal pressure. To validate our model, we compare the simulated FFR with the measured FFR by pressure guide wires examination of 20 patients. The FFR simulated by our model shows a good agreement with the measured FFR by pressure guide wires examination ( r= 0.989, 0.001). Our proposed personalized pulmonary circulation model is shown to be capable of non-invasively calculating FFR with sufficient accuracy. The FFR calculated by our personalized circulation model may effectively contribute to non-invasive detection of pulmonary artery stenosis and to a comprehensive evaluation of the entire pulmonary artery vascular tree.

Mechanical thrombectomy for pulmonary embolism in patients with patent foramen Ovale

BackgroundThe current level of evidence for mechanical thrombectomy (MT) of pulmonary embolism (PE) in patients with patent foramen ovale (PFO) is limited.ResultsThis was a retrospective analysis of 9 patients with PFO and acute high-risk or intermediate-high-risk PE, 6 with intermediate-high risk and 3 with high-risk PE. All underwent MT using the Inari FlowTriever System from Dec 2018 to November 2019. Six of these patients had confirmed deep venous thrombosis. The technical and clinical success rate for MT in all patients was 100% and 77.8%, respectively. Right-heart strain improved in 6/8 patients on follow-up echocardiography. Mean main pulmonary artery (MPA) pressure significantly decreased after MT (p < 0.012). One patient presented with altered mental status (somnolence and disorientation) prior to coronary artery angiogram and thrombectomy, developed a middle cerebral artery embolic stroke 1 day after MT, and recovered with minor sequalae and later was discharged. There was no in-hospital mortality.ConclusionsMT using FlowTriever was feasible and safe, successfully improving MPA pressure in patients presenting with concurrent PFO and PE.

Abstract 14310: Elephant Sitting on My Chest: A Tale of Two Vessels

Introduction: A dilated main pulmonary artery (MPA) seen in congenital heart disease (CHD) or pulmonary arterial hypertension (PAH) is a rare cause of angina due to left main coronary artery (LMCA) compression. Case: A 49 year old male with no prior cardiac history presented with substernal chest pain. He reported exercise intolerance for several years. On exam he had an oxygen saturation of 85%, loud P2, fixed split second heart sound and ejection click. Electrocardiogram showed right ventricular (RV) hypertrophy and no significant ST changes. Laboratory data revealed a negative troponin. An enlarged main and right pulmonary artery (RPA) (Figure 1A) was seen on computed tomography (CT) chest angiography for pulmonary embolism (CTPE) and on echocardiography he had a severely dilated RV with decreased function (Figure 1B,1C). Cardiac catheterization showed a step up in saturations from 56 to 71%, Qp:Qs of 1.5 mean MPA pressure of 53 mmHg, pulmonary capillary wedge pressure of 11mmHg and pulmonary vascular resistance (PVR) of 7WU. A slit-like narrowing of LMCA ostium was seen on coronary angiography and intravascular ultrasound (Figure 1D). He was diagnosed with a sinus venosus defect, anomalous right upper pulmonary venous drainage and suspicion for extrinsic compression of LMCA by the dilated RPA that was confirmed on cardiac CT (Figure 1E-I). He was started on triple therapy for PAH with a significant reduction in PA pressures (mean 36 mmHg and PVR 2.1 WU). Percutaneous stenting of the LMCA was deferred and he underwent successful sinus venosus defect repair with a 5mm fenestrated patch, baffling of the anomalous pulmonary veins and a 32 mm interposition graft in the MPA with reduction plasty of MPA/RPA. Conclusion: This is an unusual presentation of unrepaired CHD with angina due to a compressed LMCA from a dilated pulmonary artery. Treatment of the underlying PAH as well as repair of the defect including reduction plasty of the MPA is a consideration for symptomatic relief.

Effects of Red Blood Cell Sickling on Right Ventricular Afterload in vivo.

Hemolysis in sickle cell disease (SCD) releases cell free hemoglobin, which scavenges nitric oxide (NO), leading to pulmonary vascular vasoconstriction, increased pulmonary vascular resistance (PVR), and the development of PH. However, PVR is only one component of right ventricular (RV) afterload. Whether sickled red blood cells increase the total RV afterload, including compliance and wave reflections, is unclear. Patients with SCD and pulmonary hypertension (PH) have a significantly increased risk of sudden death compared to patients with SCD alone. Sickled red blood cells (RBCs) are fragile and lyse easily. Here, we sought to determine the acute effects of SCD RBCs and increased cell free hemoglobin on RV afterload. Main pulmonary artery pressures and flows were measured in C57BL6 mice before and after exchanges of whole blood (~200 uL, Hct=45%) with an equal volume of SCD RBCs in plasma (Hct=45%) or cell free hemoglobin (Hb+) in solution. After transfusions, animals were additionally stressed with acute hypoxia (AH; 10% O2). SCD RBCs increased PVR only compared to control RBCs; cell free hemoglobin increased PVR and wave reflections. These increases in RV afterload increased further with AH. The release of cell free hemoglobin from fragile SCD RBCs in vivo increases the total RV afterload and may impair RV function more than the SCD RBCs themselves.

Characteristics of Patent Ductus Arteriosus in Congenital Rubella Syndrome

This study investigated the characteristics of congenital rubella syndrome (CRS)-associated cardiac complications, particularly patent ductus arteriosus (PDA). We reviewed the medical records of patients with CRS who were admitted to the Children’s Hospital 1 in Vietnam between December 2010 and December 2012, and patients with CRS who underwent PDA transcatheter occlusion therapy at the cardiology department between December 2009 and December 2015. We compared the characteristics of PDA treated with transcatheter closure between children with CRS (CRS-PDA) and those without CRS (non-CRS-PDA) who underwent PDA transcatheter closure between July 2014 and December 2015. One-hundred-and-eight children with CRS were enrolled. Cardiac defects (99%), cataracts (72%), and hearing impairment (7%) were detected. Fifty CRS-PDA and 290 non-CRS-PDA patients were examined. CRS-PDA patients had smaller median birthweight (p < 0.001), more frequent pulmonary (p < 0.001) and aortic stenosis (p < 0.001), higher main pulmonary artery pressure, and higher aortic pressure in systole/diastole (p < 0.001 for each) than did non-CRS-PDA patients. The proportion of tubular-type PDA was higher in CRS-PDA patients (16%) than in non-CRS-PDA patients (3%) (p = 0.020). Tubular-type PDA was frequently seen in patients with CRS and accompanied by pulmonary/systemic hypertension and pulmonary/aortic stenosis; in these patients, more cautious device selection is needed for transcatheter PDA closure.

Sensitivity analysis and uncertainty quantification of 1-D models of pulmonary hemodynamics in mice under control and hypertensive conditions.

Pulmonary hypertension (PH), defined as an elevated mean blood pressure in the main pulmonary artery (MPA) at rest, is associated with vascular remodeling of both large and small arteries. PH has several sub-types that are all linked to high mortality rates. In this study, we use a one-dimensional (1-D) fluid dynamics model driven by in vivo measurements of MPA flow to understand how model parameters and network size influence MPA pressure predictions in the presence of PH. We compare model predictions with in vivo MPA pressure measurements from a control and a hypertensive mouse and analyze results in three networks of increasing complexity, extracted from micro-computed tomography (micro-CT) images. We introduce global scaling factors for boundary condition parameters and perform local and global sensitivity analysis to calculate parameter influence on model predictions of MPA pressure and correlation analysis to determine a subset of identifiable parameters. These are inferred using frequentist optimization and Bayesian inference via the Delayed Rejection Adaptive Metropolis (DRAM) algorithm. Frequentist and Bayesian uncertainty is computed for model parameters and MPA pressure predictions. Results show that MPA pressure predictions are most sensitive to distal vascular resistance and that parameter influence changes with increasing network complexity. Our outcomes suggest that PH leads to increased vascular stiffness and decreased peripheral compliance, congruent with clinical observations.

Exercise-Induced Changes in Pulmonary Artery Stiffness in Pulmonary Hypertension.

Background: Pulmonary hypertension causes pulmonary artery (PA) stiffening, which overloads the right ventricle (RV). Since symptoms of pulmonary hypertension (PH) are exacerbated by exercise, exercise-induced PA stiffening is relevant to cardiopulmonary status. Here, we sought to demonstrate the feasibility of using magnetic resonance imaging (MRI) for non-invasive assessment of exercise-induced changes in PA stiffness in patients with PH.Methods: MRI was performed on 7 PH patients and 8 age-matched control subjects at rest and during exercise stress. Main pulmonary artery (MPA) relative area change (RAC) and pulse wave velocity (PWV) were measured from 2D-PC images. Invasive right heart catheterization (RHC) was performed on 5 of the PH patients in conjunction with exercise stress to measure MPA pressures and stiffness index (β).Results: Heart rate and cardiac index (CI) were significantly increased with exercise in both groups. In controls, RAC decreased from 0.27 ± 0.05 at rest to 0.22 ± 0.06 with exercise (P < 0.05); a modest increase in PWV was not significant (P = 0.06). In PH patients, RAC decreased from 0.15 ± 0.02 to 0.11 ± 0.01 (P < 0.05) and PWV and β increased from 3.9 ± 0.54 m/s and 1.86 ± 0.12 at rest to 5.75 ± 0.70 m/s and 3.25 ± 0.26 with exercise (P < 0.05 for both), respectively. These results confirm increased MPA stiffness with exercise stress in both groups and the non-invasive metrics of MPA stiffness correlated well with β. Finally, as assessed by PWV but not RAC, PA stiffness of PH patients increased more than that of controls for comparable levels of moderate exercise.Conclusion: These results demonstrate the feasibility of using MRI for non-invasive assessment of exercise-induced changes in MPA stiffness in a small, heterogeneous group of PH patients in a research context. Similar measurements in a larger cohort are required to investigate differences between PWV and RAC for estimation of MPA stiffness.

Black Oesophagus as the Terminal Event in Severe Pulmonary Arterial Hypertension

We present the case of a 74-year-old nurse practitioner, who had suffered from breathlessness since December 2014, and was diagnosed with idiopathic pulmonary arterial hypertension in May 2016. Right heart catheterisation in August 2016 showed a right atrial pressure of 12 mmHg, a main pulmonary artery pressure of 51 mmHg, and a pulmonary vascular resistance of 9.0 Wood units. She was treated with tadalafil (30 mg, Septenber 2016) and ambrisentan (10 mg, October 2016), and iloprost added (April 2017). Iloprost was switched to an intravenous infusion of epoprostenol in October 2017, (peak dose 26 ng/kg/min) and continuous home oxygen. Pertussis bronchitis in July 2017 was accompanied by a reactive pleural effusion and heralded clinical deterioration with subsequent pleural effusions (transudates) requiring drainage of 1.5–2 L per week on 10 occasions. Her final admission was precipitated by a fall. She was found to be in worse right heart failure, despite taking heart failure drugs. She was treated by diuresis, paracentesis, pleurocentesis, and dobutamine for hypotension. At day 4 of treatment she reported odynophagia, her haemoglobin fell from 166 g/L to 47 g/L, and melena became manifest (despite long-term pantoprazole). Urgent gastroscopy showed black oesophagus (necrosis of distal third of the oesophagus), and diffuse duodenal bleeding and haemostasis was unable to be achieved. She died in palliative care 3 days later. Autopsy confirmed the diagnosis of idiopathic pulmonary arterial hypertension, with right ventricular hypertrophy and dilatation and ulceration of the distal oesophagus (with black slough) and duodenal ulceration. Black oesophagus is rare, and has not been reported previously in pulmonary arterial hypertension or in patients on multiple therapies for pulmonary arterial hypertension. It, nevertheless, was the terminal event in this patient with idiopathic pulmonary arterial hypertension.

Pulmonary arterial hypertension in children: diagnosis using ratio of main pulmonary artery to ascending aorta diameter as determined by multi-detector computed tomography.

The ratio of the transverse diameter of the main pulmonary artery (MPA) to ascending aorta as determined at multi-detector CT is a tool that can be used to assess the pulmonary arterial size in cases of pulmonary arterial hypertension in children. To establish a ratio of MPA to ascending aorta diameter using multi-detector CT imaging suggestive of pulmonary arterial hypertension in children. We hypothesize that a defined ratio of MPA to ascending aorta is identifiable on multi-detector CT and that higher ratios can be used to reliably diagnose the presence of pulmonary arterial hypertension in children. We calculated the multi-detector CT ratio of MPA to ascending aorta diameter in 44 children with documented pulmonary arterial hypertension by right heart catheterization and in 44 age- and gender-matched control children with no predisposing factors for pulmonary arterial hypertension. We compared this multi-detector-CT-determined ratio with the MPA pressure in the study group, as well as with the ratio of MPA to ascending aorta in the control group. A threshold ratio value was calculated to accurately identify children with pulmonary arterial hypertension. Children with documented primary pulmonary arterial hypertension have a significantly higher ratio of MPA to ascending aorta (1.46) than children without pulmonary arterial hypertension (1.11). A ratio of 1.3 carries a positive likelihood of 34 and a positive predictive value of 97% for the diagnosis of pulmonary arterial hypertension. The pulmonary arteries were larger in children with pulmonary arterial hypertension than in a control group of normal children. A CT-measured ratio of MPA to ascending aorta of 1.3 should raise the suspicion of pulmonary arterial hypertension in children.

Abstract No. 508 - Main pulmonary artery pressures measurements before and after hemodialysis access thrombectomy/thrombolysis: conventional versus a novel ‘protected’ technique

Abstract No. 508 - Main pulmonary artery pressures measurements before and after hemodialysis access thrombectomy/thrombolysis: conventional versus a novel ‘protected’ technique

Circulation : Clinical Summaries

<i>Circulation</i> : Clinical Summaries

Adjusting for Risk Associated With Pediatric and Congenital Cardiac Catheterization: A Report From the NCDR IMPACT Registry.

As US health care increasingly focuses on outcomes as a means for quantifying quality, there is a growing demand for risk models that can account for the variability of patients treated at different hospitals so that equitable comparisons between institutions can be made. We sought to apply aspects of prior risk-standardization methodology to begin development of a risk-standardization tool for the National Cardiovascular Data Registry (NCDR) IMPACT (Improving Pediatric and Adult Congenital Treatment) Registry. Using IMPACT, we identified all patients undergoing diagnostic or interventional cardiac catheterization between January 2011 and March 2013. Multivariable hierarchical logistic regression was used to identify patient and procedural characteristics predictive of experiencing a major adverse event after cardiac catheterization. A total of 19,608 cardiac catheterizations were performed between January 2011 and March 2013. Among all cases, a major adverse event occurred in 378 of all cases (1.9%). After multivariable adjustment, 8 variables were identified as critical for risk standardization: patient age, renal insufficiency, single-ventricle physiology, procedure-type risk group, low systemic saturation, low mixed venous saturation, elevated systemic ventricular end-diastolic pressure, and elevated main pulmonary artery pressures. The model had good discrimination (C statistic, 0.70), confirmed by bootstrap validation (validation C statistic, 0.69). Using prior risk-standardization efforts as a foundation, we developed and internally validated a model to predict the occurrence of a major adverse event after cardiac catheterization for congenital heart disease. Future efforts should be directed toward further refinement of the model variables within this large, multicenter data set.

Ultrasound-Accelerated Catheter-Directed Thrombolysis for Acute Submassive Pulmonary Embolism

PurposeTo evaluate the safety and efficacy of ultrasound-accelerated catheter-directed thrombolysis (USAT) in patients with submassive pulmonary embolism (PE). Materials and MethodsThis retrospective study comprised 45 consecutive patients (15 prospective, 30 retrospective) who underwent USAT for submassive PE from June 2012–May 2014. Inclusion criteria were right ventricular dysfunction (RVD) as indicated by right ventricle-to-left ventricle (RV:LV) ratio > 0.9, symptoms of < 2 weeksʼ duration, and absence of absolute contraindication to thrombolysis. All patients underwent pulmonary artery catheterization with a standardized protocol (24 mg recombinant tissue plasminogen activator). Hemodynamic evaluation immediately after USAT, RV:LV ratio evaluation at 48–72 hours after USAT by computed tomography angiography and echocardiography, and adverse event reporting for a minimum of 30 days were performed. Outcomes and complications are reported as per the Society of Interventional Radiology Reporting Standards for Endovascular Treatment of Pulmonary Embolism. ResultsUSAT was technically successful in 100% (n = 45) of patients. Main pulmonary artery pressure significantly decreased from 49.8 mm Hg to 31.1 mm Hg (P < .0001). RVD significantly improved with mean RV:LV ratios decreasing from 1.59 to 0.93 (P < .0001). There were 6 complications: 4 minor bleeding episodes at access sites and 2 major bleeding complications (flank and arm hematoma). All-cause mortality at 30 days was 0%. There were no readmissions for PE at 30 days after discharge. ConclusionsUltrasound-accelerated catheter-directed thrombolysis using a standardized low-dose protocol is a safe and efficacious method of treatment of submassive PE to reduce acute pulmonary hypertension and RVD.

5:18 PM, Abstract No. 158 - Safety and efficacy of ultrasound-accelerated thrombolysis for the treatment of submassive pulmonary embolism

Standards for Endovascular Treatment of Pulmonary Embolism. Results: CDT was technically successful in 100% (n1⁄445) of patients. Main pulmonary artery pressure significantly decreased from 49.8 mm to 31.1 mm (po0.0001). Right ventricle dysfunction significantly improved with mean RV/ LV ratios decreasing from 1.59 to 0.93 (po0.0001). There were 6 complications: 4 minor bleeding episodes at access sites, and 2 major bleeding complications (flank and arm hematoma). All cause mortality at 30 days was 0%. There were no re-admissions for PE at 30 days after discharge in all patients. Conclusion: CDT is a safe and efficacious method in the treatment of SPE to reduce acute pulmonary hypertension and RVD. Using a standardized protocol for pulmonary thrombolysis may allow for more widespread adoption of interventional therapy.

Anomalous Origin of the Right Pulmonary Artery from the Ascending Aorta: A Surgical Case Study in an Adult Patient with “Irreversible” Pulmonary Vascular Disease

An adult patient presented with an anomalous right pulmonary artery arising from the ascending aorta with severe unilateral pulmonary vascular disease of the left lung due to a large left-sided patent ductus arteriosus. A stenosis in the right pulmonary artery protected the right pulmonary vasculature. Right ventricular pressure was suprasystemic. After ductal ligation and surgical repair, pulmonary artery pressures fell dramatically. An immediate postoperative angiography confirmed extremely poor perfusion of the left lung. At four-and-a-half years of follow-up, the patient's quality of life had improved dramatically, main pulmonary artery pressure was one-sixth of systemic pressures, and there was vastly improved perfusion of the left lung at this lower perfusion pressure. The calculated pulmonary vascular resistance of the left lung was within normal limits. These findings suggested a significant degree of reversal of pulmonary hypertensive disease in the left lung sustained to 54 months postoperatively.

Noninvasive Methods for Determining Pulmonary Vascular Function in Children with Pulmonary Arterial Hypertension: Application of a Mechanical Oscillator Model

Noninvasive diagnostics for pulmonary arterial hypertension (PAH) have traditionally sought to predict main pulmonary artery pressure from qualitative or direct quantitative measures of the flow velocity pattern obtained from spectral Doppler ultrasound examination of the main pulmonary artery. A more detailed quantification of flow velocity patterns in the systemic circuit has been obtained by parameterizing the flow trace with a simple dynamic system model. Here, we investigate such a model's utility as a noninvasive predictor of total right heart afterload and right heart function. Flow velocity and pressure was measured within the main pulmonary artery during right heart catheterization of patients with normal hemodynamics (19 subjects, 20 conditions) and those with PAH undergoing reactivity evaluation (34 patients, 69 conditions). Our model parameters were obtained by least-squares fitting the model velocity to the measured flow velocity. Five parameter means displayed significant (P < .05) differences between normotensive and hypertensive groups. The model stiffness parameter correlated to actual pulmonary vascular resistance (r = 0.4924), pulmonary vascular stiffness (r = 0.6811), pulmonary flow (r = 0.6963), and stroke work (r = 0.7017), while the model initial displacement parameter had good correlation to stiffness (r = 0.6943) and flow (r = 0.6958). As predictors of total right heart afterload (resistance and stiffness) and right ventricle work, the model parameters of stiffness and initial displacement offer more comprehensive measures of the disease state than previous noninvasive methods and may be useful in routine diagnostic monitoring of patients with PAH.

Percutaneous selective pulmonary artery bands (Joeys) in a pulmonary overcirculation model

Control of distal pulmonary artery (PA) pressure and flow is a critical step in palliating infants with complex congential heart disease. Surgical procedures to protect or isolate the pulmonary circulation carry significant risk and can be unpredictable. Interventional control of pulmonary pressure/flow with an intravascular device (band) could reduce risk and improve regulation of pulmonary flow. Internal pulmonary bands were created from woven nitinol to create an internal orifice estimated to reduce distal pulmonary arterial pressure by 50%. Two designs were tested, a single eccentric lumen and two symmetrical lumens. The devices were approximately 7-mm long and the external diameter varied to suit the pulmonary arterial lumen size. A total of 15 devices were implanted in seven lambs with a stented ductus arteriosus to create high pulmonary pressure/flow. Four lambs were followed with devices and stent in place for a mean of 37 +/- 13 days. Fourteen of 15 devices were successfully implanted. One was acutely removed since the size was too large. Both device designs created greater than a 50% reduction in distal pulmonary pressure. Main PA pressure was 70/38, mean 50 +/- 13 mm Hg, and distal PA pressure 25/16, mean 20 +/- 7 mm Hg (P < 0.05). Angiography demonstrated protection of the internal banded pulmonary segments from overcirculation. Late follow-up showed that the device lumen(s) remained patent. Histology showed the vessel media to be intact but there was intimal proliferation where the device approximated the wall. There were no thrombotic emboli detected. Percutaneous internal banding of the pulmonary arteries was feasible and successful in lambs with high pulmonary flow/pressure analogous to infants with complex congenital heart disease.

Pulmonary Vascular Resistance and Impedance in Isolated Mouse Lungs: Effects of Pulmonary Emboli

To study pulsatile pressure-flow rate relationships in the intact pulmonary vascular network of mice, we developed a protocol for measuring pulmonary vascular resistance and impedance in isolated, ventilated, and perfused mouse lungs. We used pulmonary emboli to validate the effect of vascular obstruction on resistance and impedance. Main pulmonary artery and left atrial pressures and pulmonary vascular flow rate were measured under steady and pulsatile conditions in the lungs of C57BL/6J mice (n = 6) before and after two infusions with 25 microm-diameter microspheres (one million per infusion). After the first and second embolizations, pulmonary artery pressures increased approximately two-fold and three and a half-fold, respectively, compared to baseline, at a steady flow rate of 1 ml/min (P < 0.05). Pulmonary vascular resistance and 0 Hz impedance also increased after the first and second embolizations for all flow rates tested (P < 0.05). Frequency-dependent features of the pulmonary vascular impedance spectrum were suggestive of shifts in the major pulmonary vascular reflection sites with embolization. Our results demonstrate that pulmonary artery pressure, resistance, and impedance magnitude measured in this isolated lung setup changed in ways consistent with in vivo studies in larger animals and humans and demonstrate the usefulness of the isolated, ventilated, and perfused mouse lung for investigating steady and pulsatile pressure-flow rate relationships.

Non-Anti-Galα1-3Gal Antibody Mechanisms Are Sufficient to Cause Hyperacute Lung Dysfunction in Pulmonary Xenotransplantation1

Hyperacute lung dysfunction, which is always associated with pulmonary pig-to-primate xenotransplantation is not well understood. The mechanisms associated with its occurrence seem to differ from mechanisms involved in hyperacute xenograft rejection seen in porcine hearts or kidneys transplanted into primates. To determine the contribution of anti-Gal alpha1-3Gal antibodies (alphaGAb) in such a process, we performed a set of orthotopic pig lung transplants into baboons depleted of alphaGAb and compared graft function and survival with those receiving only immunosuppression. Pigs expressing human membrane cofactor protein served as donors. All baboons received triple immunosuppressive therapy. Depletion of alphaGAb in the experimental group (n = 4) was done by way of immunoadsorption using immunoaffinity membranes. Controls (n = 4) did not undergo immunoadsorption. Orthotopic lung transplants were performed through a left thoracotomy. Main pulmonary artery blood flow and pressure, left pulmonary artery blood flow, and left atrial pressure were recorded. At 1 hour after reperfusion, pulmonary artery graft flows and pulmonary vascular resistances (PVR) were better in animals depleted of alphaGAb than in controls (605 +/- 325.2 mL/min versus 230 +/- 21 mL/min; 27.1 +/- 41.3 mmHg/L/min versus 63 +/- 1 mmHg/L/min). But at 3 hours after reperfusion average graft flows in baboons depleted of alphaGAb had decreased to 277.6 +/- 302.2 mL/min and PVRs had increased 58.3 +/- 42.0 mmHg/L/min. On the other hand, controls maintained stable flows and PVRs (223 +/- 23 mL/min; 61 +/- 3 mmHg/L/min). Survival was ultimately better in control baboons when compared with alphaGAb depleted ones (12.2 +/- 3.3 h versus 4.4 +/- 3.2 h). Unlike heart and kidney xenograft transplants, hyperacute lung xenograft dysfunction seems to be mediated by factors other than alphaGAb.