Prognostic Value and Determinants of High-Sensitivity Cardiac Troponin T in Patients With a Systemic Right Ventricle: Insights From the SERVE Trial.

BACKGROUND: The determinants and prognostic value of high-sensitivity cardiac troponin T (hs-cTnT) among patients with a systemic right ventricle are largely unknown. METHODS AND RESULTS: Ninety-eight patients from the randomized controlled SERVE (Effect of Phosphodiesterase-5 Inhibition With Tadalafil on Systemic Right Ventricular Size and Function) trial were included. The correlation between baseline hs-cTnT concentrations and biventricular volumes and function quantified by cardiac magnetic resonance or cardiac multirow detector computed tomography was assessed by adjusted linear regression models. The prognostic value of hs-cTnT was assessed by adjusted Cox proportional hazards models, survival analysis, and concordance statistics. The primary outcome was time to the composite of clinically relevant arrhythmia, hospitalization for heart failure, or all-cause death. Median age was 39 (interquartile range, 32-48) years, and 32% were women. Median hs-cTnT concentration was 7 (interquartile range, 4-11) ng/L. Coefficients of determination for the relationship between hs-cTnT concentrations and right ventricular end-systolic volume index and right ventricular ejection fraction (RVEF) were +0.368 (P=0.046) and -0.381 (P=0.018), respectively. The sex- and age-adjusted hazard ratio for the primary outcome of hs-cTnT at 2 and 4 times the reference level (5 ng/L) were 2.89 (95% CI, 1.14-7.29) and 4.42 (95% CI, 1.21-16.15), respectively. The prognostic performance quantified by the concordance statistics for age- and sex-adjusted models based on hs-cTnT, right ventricular ejection fraction, and peak oxygen uptake predicted were comparable: 0.71% (95% CI, 0.61-0.82), 0.72% (95% CI, 0.59-0.84), and 0.71% (95% CI, 0.59-0.83), respectively. CONCLUSIONS: Hs-cTnT concentration was significantly correlated with right ventricular ejection fraction and right ventricular end-systolic volume index in patients with a systemic right ventricle. The prognostic accuracy of hs-cTnT was comparable to that of right ventricular ejection fraction and peak oxygen uptake predicted. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03049540.

Right Ventricular Myocardial Infarction-A Tale of Two Ventricles: JACC Focus Seminar 1/5.

Right ventricular infarction (RVI) complicates 50% of cases of acute inferior ST-segment elevation myocardial infarction, and is associated with high in-hospital morbidity and mortality. Ischemic right ventricular (RV) systolic dysfunction decreases left ventricular preload delivery, resulting in low-output hypotension with clear lungs, and disproportionate right heart failure. RV systolic performance is generated by left ventricular contractile contributions mediated by the septum. Augmented right atrial contraction optimizes RV performance, whereas very proximal occlusions induce right atrial ischemia exacerbating hemodynamic compromise. RVI is associated with vagal mediated bradyarrhythmias, both during acute occlusion and abruptly with reperfusion. The ischemic dilated RV is also prone to malignant ventricular arrhythmias. Nevertheless, RV is remarkably resistant to infarction. Reperfusion facilitates RV recovery, even after prolonged occlusion and in patients with severe shock. However, in some cases hemodynamic compromise persists, necessitating pharmacological and mechanical circulatory support with dedicated RV assist devices as a "bridge to recovery."

Prognostic value of the echocardiographic ratio tricuspid annular plane systolic excursion / pulmonary arterial systolic pressure in acute pulmonary embolism.

INTRODUCTION: The occurrence of death from acute pulmonary embolism (PE) is often linked to right ventricular (RV) failure, arising from an imbalance between RV systolic function and heightened RV afterload. In our study, we posited that an echocardiographic ratio derived from this disparity [RV systolic function assessed by tricuspid annular plane systolic excursion (TAPSE) divided by pulmonary arterial systolic pressure (PASP)] could offer superior predictive value for adverse outcomes compared to individual measurements of TAPSE and PASP alone. METHODS: We conducted a retrospective analysis using data from a University Hospital Centre spanning from 2017 to 2023. All individuals with confirmed PE and a formal transthoracic echocardiogram within 7 days of diagnosis were included. The primary endpoint was a composite outcome of death, hemodynamic deterioration needing introduction of inotropes or thrombolysis within 30 days. Secondary endpoints included 6 months all-cause mortality and onset of right-sided heart failure. RESULTS: Thirty-eight patients were included. Mean age was 58 ±15 years old. A male predominance was noted: 23 male patients (60.5%) and 15 female patients (39.5%). Eight patients met the primary composite endpoint while nine patients met the secondary composite endpoint. In multivariate analysis, the TAPSE/PASP ratio was independently associated with the primary outcome (OR=2.77, 95% CI 1.101-10.23, P=0.042). A TAPSE/PASP ratio <0.3 was independently associated with the secondary outcome (OR=3.07, 95% CI 1.185-10.18, P=0.034). CONCLUSION: This study suggests that a combined echocardiographic ratio of RV function to afterload is effective in predicting adverse outcomes in acute PE.

Impact of right ventricular dysfunction on outcomes in patients requiring intra-aortic balloon pump placement: A retrospective nationwide analysis (2016-2020).

Right ventricular dysfunction (RVD) continues to be a significant contributor to both mortality and morbidity, posing a significant challenge in the management of patients undergoing evaluation for mechanical circulatory support (MCS). Currently, there is a paucity of data regarding outcomes in this subset of patients. We analyzed the National Inpatient Sample database (NIS) to identify adult hospitalizations who underwent intra-aortic balloon pump (IABP) placement with or without co-existence of RVD. Multivariate logistic regression, and linear regression analyses were used to compare outcomes, and adjust for possible confounders. Out of 126,985 hospitalizations who underwent IABP placement, 1,475 (1.2%) had RVD. Patients with RVD who received an IABP had higher adjusted odds of inpatient mortality (Adjusted odds ratio [aOR]: 2.33, 95% confidence interval [CI]: 1.7-3.2, p<0.001) than those without co-existing RVD. Hospitalized patients who underwent IABP placement with RVD had higher adjusted odds of worse hospitalization outcomes in general. Conducting additional prospective studies and clinical trials with an emphasis on further subcategorization of patients with RVD is crucial for determining optimal management strategies for these patients.

Heterogeneity of right ventricular echocardiographic parameters in systemic lupus erythematosus among four clinical subgroups, as stratified by clinical organ involvement in observational cohort.

BACKGROUND: Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease. Cardiac involvement in SLE is rare but plays an important prognostic role. The degree of cardiac involvement according to SLE subsets defined by non-cardiac manifestations is unknown. The objective of this study was to identify differences in transthoracic echocardiography (TTE) parameters associated with different SLE subgroups. METHODS: One hundred eighty-one patients who fulfilled the 2019 American College of Rheumatology/EULAR classification criteria for SLE and underwent baseline TTE were included in this cross-sectional study. We defined four subsets of SLE based on the predominant clinical manifestations. A multivariate multinomial regression analysis was performed to determine whether TTE parameters differed between groups. RESULTS: Four clinical subsets were defined according to non-cardiac clinical manifestations: group A (n=37 patients) showed features of mixed connective tissue disease, group B (n=76 patients) had primarily cutaneous involvement, group C (n=18) exhibited prominent serositis and group D (n=50) had severe, multi-organ involvement, including notable renal disease. Forty TTE parameters were assessed between groups. Per multivariate multinomial regression analysis, there were statistically significant differences in early diastolic tricuspid annular velocity (RV-Ea, p<0.0001), RV S' wave (p=0.0031) and RV end-diastolic diameter (p=0.0419) between the groups. Group B (primarily cutaneous involvement) had the lowest degree of RV dysfunction. CONCLUSION: When defining clinical phenotypes of SLE based on organ involvement, we found four distinct subgroups which showed notable differences in RV function on TTE. Risk-stratifying patients by clinical phenotype could help better tailor cardiac follow-up in this population.

Echocardiographic diagnosis and clinical implications of wide-open tricuspid regurgitation for evaluating right ventricular dysfunction in the emergency department.

The tricuspid regurgitation pressure gradient (TRPG) reflects the difference in pressure between the right ventricle and right atrium (ΔPRV-RA). Its estimation by echocardiography correlates well with that obtained using right-heart catheterization. An elevated TRPG is an important marker for identifying right ventricular dysfunction in both the acute and chronic settings. However, in the "wide-open" variant of TR, the TRPG counterintuitively falls. Failure to recognize this potential pitfall and underlying pathophysiology can cause underestimation of the severity of right ventricular dysfunction. This could lead to erroneous fluid tolerance assessments, and potentially harmful resuscitative and airway management strategies. In this manuscript, we illustrate the pathophysiology and potential pitfall of wide-open TR through a series of cases in which emergency physicians made the diagnosis using cardiac point-of-care ultrasound. To our knowledge, this clinical series is the first to demonstrate recognition of the paradoxically-low TRPG of wide-open TR, which guided appropriate management of critically ill patients in the emergency department.

Immediate cardiopulmonary responses to consecutive pulmonary embolism: a randomized, controlled, experimental study.

BACKGROUND: Acute pulmonary embolism (PE) induces ventilation-perfusion mismatch and hypoxia and increases pulmonary pressure and right ventricular (RV) afterload, entailing potentially fatal RV failure within a short timeframe. Cardiopulmonary factors may respond differently to increased clot burden. We aimed to elucidate immediate cardiopulmonary responses during successive PE episodes in a porcine model. METHODS: This was a randomized, controlled, blinded study of repeated measurements. Twelve pigs were randomly assigned to receive sham procedures or consecutive PEs every 15 min until doubling of mean pulmonary pressure. Cardiopulmonary assessments were conducted at 1, 2, 5, and 13 min after each PE using pressure-volume loops, invasive pressures, and arterial and mixed venous blood gas analyses. ANOVA and mixed-model statistical analyses were applied. RESULTS: Pulmonary pressures increased after the initial PE administration (p < 0.0001), with a higher pulmonary pressure change compared to pressure change observed after the following PEs. Conversely, RV arterial elastance and pulmonary vascular resistance was not increased after the first PE, but after three PEs an increase was observed (p = 0.0103 and p = 0.0015, respectively). RV dilatation occurred following initial PEs, while RV ejection fraction declined after the third PE (p = 0.004). RV coupling exhibited a decreasing trend from the first PE (p = 0.095), despite increased mechanical work (p = 0.003). Ventilatory variables displayed more incremental changes with successive PEs. CONCLUSION: In an experimental model of consecutive PE, RV afterload elevation and dysfunction manifested after the third PE, in contrast to pulmonary pressure that increased after the first PE. Ventilatory variables exhibited a more direct association with clot burden.

The right ventricle outflow tract systolic function could predict the severity of the cirrhosis.

Background/aim: The distinctive liver framework is converted into structurally abnormal nodules as a consequence of tissue fibrosis in cirrhosis. Cardiac dysfunction in cirrhosis was described, and the term "cirrhotic cardiomyopathy (CCM)" was coined to describe this syndrome. Recent research has shown that the contractile characteristics of the right ventricular outflow tract (RVOT) have a significant impact on right ventricular functions. The right ventricular outflow tract-systolic excursion is an important systolic function marker of RVOT (RVOT-SE). There has yet to be published research on RVOT function in cirrhotic patients. We looked at the relationship between cirrhosis severity and the RVOT-SE. Materials and methods: Sixty-nine consecutive hepatic cirrhotic patients were recruited for the research between June 1, 2018 and January 1, 2022. A medical history, thorough physical examination, laboratory investigations, echocardiographic evaluation, and RVOT-SE were obtained. The patients were separated into two groups: those with compensated cirrhosis (Child-Pugh class 1) and those with decompensated cirrhosis (Child-Pugh class 2 and 3). Results: On the numerous standard echocardiographic parameters that examined the diameter and function of the left ventricle, we observed no significant difference between groups. Nevertheless, a statistically significant difference in Right Ventricle Wall (RVW) (p = 0.014), systolic pulmonary artery pressure (sPAP) (p = 0.034), RVOT-SE (p = 0.003), and Tricuspid Annular Plane Systolic Excursion (TAPSE) (p = 0.042) was detected across cirrhosis groups. The RVOT-SE had a positive correlation with cirrhosis severity (OR: 0.607; 95% CI: 0.425-0.866; p = 0.006), according to multiple logistic regression studies. According to the ROC curve study, RVOT-SE 8.8 cm/s predicted decompensated cirrhosis with 72% sensitivity and 72.7% specificity (AUC = 0.715, p: 0.001). Conclusion: In the current study, we found that RVOT-SE was related to the severity of cirrhosis. Larger patient cohorts and multi-center investigations will provide light on the notion.

4-hydroxysesamin protects rat with right ventricular failure due to pulmonary hypertension by inhibiting JNK/p38 MAPK signaling.

The specific mechanism of 4-hydroxysesamin (4-HS), a modification of Sesamin, on right ventricular failure due to pulmonary hypertension (PH) is ominous. By creating a rat model of PH in vivo and a model of pulmonary artery smooth muscle cell (PASMC) hypoxia and inflammation in vitro, the current work aimed to investigate in depth the molecular mechanism of the protective effect of 4-HS. In an in vitro model of hypoxia PASMC, changes in cell proliferation and inflammatory factors were detected after treatment with 4-HS, followed by changes in the JNK/p38 MAPK signaling pathway as detected by Western blot signaling pathway. The findings demonstrated that 4-HS was able to minimize PASMC cell death, block the JNK/p38 MAPK signaling pathway, and resist the promoting effect of hypoxia on PASMC cell proliferation. Following that, we found that 4-HS could both mitigate the right ventricular damage brought on by MCT and had a protective impact on rats Monocrotaline (MCT)-induced PH in in vivo investigations. The key finding of this study is that 4-HS may protect against PH by inhibiting the JNK/p38 MAPK signaling pathway.

Bioactive adrenomedullin as a marker of congestion and disease progression in patients with a systemic right ventricle.

BACKGROUND: Adults with a systemic right ventricle (sRV) are at a high risk for heart failure (HF) hospitalization and mortality. Bioactive adrenomedullin (bio-ADM) has been proposed as a marker of congestion and prognosis in patients with cardiovascular disease. We aimed to evaluate the association between bio-ADM and mortality and HF events in sRV patients. METHODS: Plasma bio-ADM was measured by a novel immunoassay in plasma of 85 sRV patients. A composite endpoint of all-cause mortality and HF events was used as outcome. HF events were defined as onset or progression of HF signs or symptoms requiring hospitalization, initiation or intensification of therapy. Multivariable Cox regression analyses were performed to evaluate the association between bio-ADM and outcome. RESULTS: The mean age of the patients was 37 ± 9 years and 65% were male. Patients with higher plasma bio-ADM concentrations were more often treated with diuretics (p = 0.007), possibly because of signs and/or symptoms of congestion. During a median follow-up of 10.2 years, 33.7% of the patients reached the endpoint. After adjustment for age and N-terminal pro B-type natriuretic peptide (NT-pro BNP), higher bio-ADM levels were associated with a higher risk of the composite endpoint (hazard ratio: 2.09 [95%-confidence interval: 1.15-3.78]). Bio-ADM improved risk prediction when added to NT-proBNP and age (C-statistic improved from 0.748 to 0.776 [p = 0.03]). CONCLUSIONS: Bio-ADM can be considered as a marker of congestion and independent predictor of death and HF events in adult patients with a sRV. Moreover, in terms of risk prediction, it has added value to NT-proBNP.

Use of percutaneous mechanical circulatory support for right ventricular failure.

BACKGROUND: Utilization of right ventricular mechanical circulatory support (RV-MCS) devices has been limited by a lack of recognition of RV failure as well as a lack of availability and experience with RV-MCS. AIMS: We report a single-center experience with the use of percutaneous RV-MCS and report predictors of adverse outcomes. METHODS: This was a single-center retrospective cohort study. Data from consecutive patients who received RV-MCS for any indication between June 2015 and January 2022 were included. Data on baseline comorbidities, hemodynamics, and laboratory values were collected. The primary outcome was in-hospital mortality analyzed as a logistic outcome in a multivariable model. These variables were further ranked by their predictive value. RESULTS: Among 58 consecutive patients enrolled, the median age was 66 years, 31% were female and 53% were white. The majority of the patients (48%) were hospitalized for acute on chronic heart failure. The majority of the patients were SCAI SHOCK Stage D (67%) and 34 (64%) patients had MCS placed within 24 h of the onset of shock. Before placement of RV-MCS, median central venous pressure (CVP) and RV stroke work index were 20 mmHg and 8.9 g m/m2, respectively. Median serum lactate was 3.5 (1.6, 6.2) mmol/L. Impella RP was implanted in 50% and ProtekDuo in the remaining 50%. Left ventricular MCS was concomitantly used in 66% of patients. Twenty-eight patients (48.3%) died. In these patients, median serum lactate was significantly higher (4.1 [2.3, 13.0] vs. 2.2 [1.4, 4.0] mmol/L, p = 0.007) and a trend toward higher median CVP (24 [18, 31] vs. 19 [14, 24] mmHg, p = 0.052). In the multivariable logistic model, both serum lactate and CVP before RV-MCS placement were independent predictors of in-hospital mortality. Serum lactate had the highest predictive value. CONCLUSION: In our real-world cohort, 52% of patients treated with RV-MCS survived their index hospitalization. Serum lactate at presentation and CVP were the strongest predictors of in-hospital mortality.

Association between right ventricular global longitudinal strain and mortality in intermediate-risk pulmonary embolism.

BACKGROUND: Right ventricular (RV) systolic dysfunction has been identified as a prognostic marker for adverse clinical events in patients presenting with acute pulmonary embolism (PE). However, challenges exist in identifying RV dysfunction using conventional echocardiography techniques. Strain echocardiography is an evolving imaging modality which measures myocardial deformation and can be used as an objective index of RV systolic function. This study evaluated RV Global Longitudinal Strain (RVGLS) in patients with intermediate risk PE as a parameter of RV dysfunction, and compared to traditional echocardiographic and CT parameters evaluating short-term mortality. METHODS: Retrospective single center cohort study of 251 patients with intermediate-risk PE between 2010 and 2018. The primary outcome was all-cause mortality at 30 days. Statistical analysis evaluated each parameter comparing survivors versus non-survivors at 30 days. Receiver operating characteristic (ROC) curves and Kaplan-Meier curves were used for comparison of the two cohorts. RESULTS: Altogether 251 patients were evaluated. Overall mortality rate was 12.4%. Utilizing an ROC curve, an absolute cutoff value of 17.7 for RVGLS demonstrated a sensitivity of 93% and specificity of 70% for observed 30-day mortality. Individuals with an RVGLS ≤17.7 had a 25 times higher mortality rate than those with RVGLS above 17.7 (HR 25.24, 95% CI = 6.0-106.4, p < .001). Area under the curve was (.855), RVGLS outperformed traditional echocardiographic parameters, CT findings, and cardiac biomarkers on univariable and multivariable analysis. CONCLUSIONS: Reduced RVGLS values on initial echocardiographic assessment of patients with intermediate-risk PE identified patients at higher risk for mortality at 30 days.

Deep learning to assess right ventricular ejection fraction from two-dimensional echocardiograms in precapillary pulmonary hypertension.

BACKGROUND: Precapillary pulmonary hypertension (PH) is characterized by a sustained increase in right ventricular (RV) afterload, impairing systolic function. Two-dimensional (2D) echocardiography is the most performed cardiac imaging tool to assess RV systolic function; however, an accurate evaluation requires expertise. We aimed to develop a fully automated deep learning (DL)-based tool to estimate the RV ejection fraction (RVEF) from 2D echocardiographic videos of apical four-chamber views in patients with precapillary PH. METHODS: We identified 85 patients with suspected precapillary PH who underwent cardiac magnetic resonance imaging (MRI) and echocardiography. The data was divided into training (80%) and testing (20%) datasets, and a regression model was constructed using 3D-ResNet50. Accuracy was assessed using five-fold cross validation. RESULTS: The DL model predicted the cardiac MRI-derived RVEF with a mean absolute error of 7.67%. The DL model identified severe RV systolic dysfunction (defined as cardiac MRI-derived RVEF < 37%) with an area under the curve (AUC) of .84, which was comparable to the AUC of RV fractional area change (FAC) and tricuspid annular plane systolic excursion (TAPSE) measured by experienced sonographers (.87 and .72, respectively). To detect mild RV systolic dysfunction (defined as RVEF ≤ 45%), the AUC from the DL-predicted RVEF also demonstrated a high discriminatory power of .87, comparable to that of FAC (.90), and significantly higher than that of TAPSE (.67). CONCLUSION: The fully automated DL-based tool using 2D echocardiography could accurately estimate RVEF and exhibited a diagnostic performance for RV systolic dysfunction comparable to that of human readers.

Echocardiographic features of right ventricle in septic patients with elevated central venous pressure.

BACKGROUND: Elevated central venous pressure (CVP) is deemed as a sign of right ventricular (RV) dysfunction. We aimed to characterize the echocardiographic features of RV in septic patients with elevated CVP, and quantify associations between RV function parameters and 30-day mortality. METHODS: We retrospectively reviewed a cohort of septic patients with CVP ≥ 8 mmHg in a tertiary hospital intensive care unit. General characteristics and echocardiographic parameters including tricuspid annular plane systolic excursion (TAPSE), pulmonary vascular resistance (PVR) as well as prognostic data were collected. Associations between RV function parameters and 30-day mortality were assessed using Cox regression models. RESULTS: Echocardiography was performed in 244 septic patients with CVP ≥ 8 mmHg. Echocardiographic findings revealed that various types of abnormal RV function can occur individually or collectively. Prevalence of RV systolic dysfunction was 46%, prevalence of RV enlargement was 34%, and prevalence of PVR increase was 14%. In addition, we collected haemodynamic consequences and found that prevalence of systemic venous congestion was 16%, prevalence of RV-pulmonary artery decoupling was 34%, and prevalence of low cardiac index (CI) was 23%. The 30-day mortality of the enrolled population was 24.2%. In a Cox regression analysis, TAPSE (HR:0.542, 95% CI:0.302-0.972, p = 0.040) and PVR (HR:1.384, 95% CI:1.007-1.903, p = 0.045) were independently associated with 30-day mortality. CONCLUSIONS: Echocardiographic findings demonstrated a high prevalence of RV-related abnormalities (RV enlargement, RV systolic dysfunction and PVR increase) in septic patients with elevated CVP. Among those echocardiographic parameters, TAPSE and PVR were independently associated with 30-day mortality in these patients.

Clinical features of plastic bronchitis in children after congenital heart surgery.

BACKGROUND: Plastic bronchitis (PB) can occur in patients who have undergone congenital heart surgery (CHS). This study aimed to investigate the clinical features of PB in children after CHS. METHODS: We conducted a retrospective cohort study using the electronic medical record system. The study population consisted of children diagnosed with PB after bronchoscopy in the cardiac intensive care unit after CHS from May 2016 to October 2021. RESULTS: A total of 68 children after CHS were finally included in the study (32 in the airway abnormalities group and 36 in the right ventricular dysfunction group). All children were examined and treated with fiberoptic bronchoscopy. Pathogens were detected in the bronchoalveolar lavage fluid of 41 children, including 32 cases in the airway abnormalities group and 9 cases in the right ventricular dysfunction group. All patients were treated with antibiotics, corticosteroids (intravenous or oral), and budesonide inhalation suspension. Children with right ventricular dysfunction underwent pharmacological treatment such as reducing pulmonary arterial pressure. Clinical symptoms improved in 64 children, two of whom were treated with veno-arterial extracorporeal membrane oxygenation (ECMO) due to recurrent PB and disease progression. CONCLUSIONS: Children with airway abnormalities or right ventricular dysfunction after CHS should be alerted to the development of PB. Pharmacological treatment such as anti-infection, corticosteroids, or improvement of right ventricular function is the basis of PB treatment, while fiberoptic bronchoscopy is an essential tool for the diagnosis and treatment of PB. ECMO assistance is a vital salvage treatment for recurrent critically ill PB patients.

The Sugen/Hypoxia Rat Model for Pulmonary Hypertension and Right Heart Failure.

Pulmonary hypertension (PH) is a devastating disease, characterized by complex remodeling of the pulmonary vasculature. PH is classified into five groups based on different etiology, pathology, as well as therapy and prognosis. Animal models are essential for the study of underlying mechanisms, pathophysiology, and preclinical testing of new therapies for PH. The complexity of the disease with different clinical entities dictates the necessity for more than one animal model to resemble PH, as a single model cannot imitate the broad spectrum of human PH.Here we describe a detailed protocol for creating a rat model of PH with right ventricular (RV) failure. Furthermore, we present how to characterize it hemodynamically by invasive measurements of RV and pulmonary arterial (PA) pressures. Animals subjected to this model display severe pulmonary vascular remodeling and RV dysfunction. In this model, rats undergo a single subcutaneous injection of Sugen (SU5416, a vascular endothelial growth factor inhibitor) and are immediately exposed to chronic hypoxia in a hypoxia chamber for 3-6 weeks. This Sugen/Hypoxia rat model resembles Group 1 PH.