Usefulness of risk assessment tools in predicting hemodynamic outcome after balloon pulmonary angioplasty: a comparative analysis.

OBJECTIVES: Several parameters of widely used risk assessment tools for pulmonary arterial hypertension (PAH) have been linked to hemodynamic outcomes of balloon pulmonary angioplasty (BPA). Therefore, we aimed to determine whether these risk assessment tools could be used to predict hemodynamic outcomes following BPA. METHODS: In this retrospective study, we included 139 patients with chronic thromboembolic pulmonary hypertension who had undergone BPA at Center for Pulmonary Vascular Diseases, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College (Beijing, China). We compared the accuracies of seven well-validated risk assessment tools for predicting hemodynamic outcomes following BPA. A favorable hemodynamic outcome was defined as a mean pulmonary arterial pressure < 30 mmHg at follow-up. RESULTS: The baseline risk profiles varied significantly among the risk assessment tools. The US Registry to Evaluate Early and Long-Term PAH Disease Management risk scales and the French risk assessment tools rated most patients as high-risk, while the Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension (COMPERA) series and laboratory examination-based risk scales categorized most patients as having intermediate-risk profile. COMPERA 2.0 (4-strata) exhibited the highest predictive power among all risk stratifications. Noninvasive risk stratification (COMPERA 2.0 [3-strata]) showed a comparable predictive ability to that of invasive risk stratification (COMPERA 1.0) (area under the curve 0.649 vs. 0.648). Moreover, incorporating diffusing capacity of the lungs for carbon monoxide and tricuspid regurgitation velocity into COMPERA 2.0 (4-strata) further enhanced its predictive power (net reclassification index 0.153, 95% confidence interval 0.009-0.298, p = 0.038). Additionally, this refined COMPERA version had a high calibration accuracy (slope 0.96). CONCLUSION: Although the risk strata distribution varied among different risk assessment tools, the proportion of patients achieving favorable hemodynamics decreased with the escalation of risk stratification in most models. The well-validated risk assessment tools for PAH could also predict hemodynamic outcomes following BPA, and the refined COMPERA 2.0 model exhibited the highest predictive ability among these. Applying risk assessment tools before BPA can facilitate early identification of patients in need of closer monitoring and more intensive interventions, contributing to a better prognosis after BPA.

A pragmatic approach to risk assessment in pulmonary arterial hypertension using the 2015 European Society of Cardiology/European Respiratory Society guidelines.

OBJECTIVE: To optimise treatment of patients with pulmonary arterial hypertension (PAH), the 2015 European Society of Cardiology/European Respiratory Society guidelines recommend using risk stratification, with the aim of patients achieving low-risk status. Previous analyses of registries made progress in using risk stratification approaches, however, the focus is often on patients with a low-risk prognosis, whereas most PAH patients are in intermediate-risk or high-risk categories. Using only six parameters with high prognostic relevance, we aimed to demonstrate a pragmatic approach to individual patient risk assessment to discriminate between patients at low risk, intermediate risk and high risk of death. METHODS: Risk assessment was performed combining six parameters in four criteria: (1) WHO functional class, (2) 6 min walk distance, (3) N-terminal pro-brain natriuretic peptide (BNP)/BNP plasma levels or right atrial pressure and (4) cardiac index or mixed venous oxygen saturation. Assessments were made at baseline and at first follow-up after 3-4 months. RESULTS: 725 PAH treatment-naive patients were analysed. Survival estimates between risk groups were statistically significant at baseline and first follow-up (p<0.001), even when the analysis was performed within PAH etiological subgroups. Similar results were observed in 208 previously treated PAH patients. Furthermore, patients who remained at or improved to low risk had a significantly better estimated survival compared with patients who remained at or worsened to intermediate risk or high risk (p≤0.005). CONCLUSION: The simplified risk-assessment method can discriminate idiopathic, connective-tissue-disease-associated and congenital-heart-disease-associated PAH patients into meaningful high-risk, intermediate-risk and low-risk groups at baseline and first follow-up. This pragmatic approach reinforces targeting a low-risk profile for PAH patients.

Assessment of right ventricle in pulmonary arterial hypertension with three-dimensional echocardiography and cardiovascular magnetic resonance.

AIM: To correlate 3-D Echo and CMR RV parameters and to verify whether they are similarly related to the clinical conditions of patients with pulmonary arterial hypertension (PAH), a disease in which the RV plays a crucial prognostic role. METHODS: We enrolled 34 consecutive PAH patients followed by our PAH clinics. All patients underwent a 3-D Echo and CMR assessment of RV volumes and functions in the same day. The presence or absence of correlation between major findings was investigated; functional RV parameters were also analyzed in relation to 6-min walking test (6MWT) results and BNP/Nt-proBNP plasma levels. Twenty-four subjects served as controls. RESULTS: Good agreement was found between 3-D Echo and CMR measures of RV volumes [RV-end-diastolic volume (r = 0.72, P < 0.0001), RV-end-systolic volume (ESV) (r = 0.80, P < 0.0001)] and function [RV-EF (r = 0.73, P < 0.0001), RV-ESV/SV (r = 0.83, P = 0.001)] for all the subjects of the study. These correlations were stronger in PAH patients than in control subjects. Importantly, 3-D Echo and CMR RV-EF and RV to pulmonary arterial coupling (RV-ESV/SV) similarly correlated with BNP/Nt-proBNP levels and with functional capacity measured at 6MWT in the PAH patients group. CONCLUSIONS: 3-D Echo demonstrated a significant agreement with CMR in the assessment of RV volume and function in PAH patients. Both techniques showed a similar correlation with clinical and prognostic parameters. The use of 3-D Echo should be amply boosted in the real-world clinical evaluation of PAH patients.

Risk assessment in patients with functional class II pulmonary arterial hypertension: Comparison of physician gestalt with ESC/ERS and the REVEAL 2.0 risk score.

BACKGROUND: Accurate and regular risk assessment is important for evaluation and treatment of pulmonary arterial hypertension (PAH) patients, including those with functional class (FC) II symptoms, a population considered at low risk for disease progression. Risk assessment methods include subjective and objective evaluations. Multiparametric assessments include tools based on the European Society of Cardiology/European Respiratory Society (ESC/ERS) guidelines (COMPERA and FPHR methods, respectively) and the Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL; REVEAL 2.0 tool). To better understand risk status determination in FC II patients, we compared physician-reported risk assessments with objective multiparameter assessment tools. METHODS: This retrospective chart analysis included PAH patients with FC II symptoms receiving monotherapy or dual therapy. Physicians were surveyed (via telephone) to obtain an assessment of patient risk using their typical methodology, which might have been informed by objective risk assessment. Patient risk was then calculated independently using COMPERA, FPHR and REVEAL 2.0 tools. Factors associated with incongruent risk assessment were identified. RESULTS: Of the 153 patients, 41%, 46%, and 13% were classified as low, intermediate, and high risk, respectively, by physicians. Concordance between physician gestalt and objective methods ranged from 43%-54%. Among patients considered as low risk by physician gestalt, 4%-28% were categorized as high risk using objective methods. The most common physician factor associated with incongruent risk assessment was less frequent echocardiography during follow-up (every 7-12 months vs. every 3 months; p = 0.01). CONCLUSIONS: More than half of FC II PAH patients were classified as intermediate/high risk using objective multiparameter assessments. Incorporating objective risk-assessment algorithms into clinical practice may better inform risk assessment and treatment strategies.

Hemodynamics and risk assessment 2 years after the initiation of upfront ambrisentan‒tadalafil in pulmonary arterial hypertension.

BACKGROUND: Upfront combination therapy with ambrisentan and tadalafil has been reported to improve the condition of patients with pulmonary arterial hypertension (PAH) more than with either drug alone. However, little is known about the long-term associated changes in hemodynamics and risk assessment scores. METHODS: This was a multicenter, retrospective analysis of clinical data in 106 patients with newly diagnosed PAH. Clinical evaluations, including demographics, medical history, World Health Organization (WHO) functional class (FC) and 6-minute walk distance (6MWD), right heart catheterization, and Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL) risk score 2.0, were assessed over 48 months of ambrisentan‒tadalafil therapy. RESULTS: At baseline, 9 patients (9%) showed a low (<7), 48 patients (45%) showed an intermediate (7-8), and 49 patients (46%) showed a high (>8) REVEAL risk score. At a median follow-up of 2 years, 45 patients (43%) showed a low, 47 patients (44%) showed an intermediate, and 14 patients (13%) showed a high REVEAL score, along with improvements in WHO FC, 6MWD and a decrease in mean pulmonary artery pressure and N-terminal pro brain natriuretic peptide (all p < 0.001). Pulmonary vascular resistance (PVR) decreased by 37% from 11.5 ± 6.5 to 7.2 ± 4.1 Wood units (p < 0.001). A total of 61 patients (57%) remained in intermediate-risk or high-risk categories. Low-risk patients had either a decrease in PVR of >50% or a stroke volume within the limits of normal. CONCLUSIONS: Initial combination therapy with ambrisentan and tadalafil in PAH improves the REVEAL risk score in proportion to decreased PVR and preserved stroke volume but still insufficiently so in approximately 50% of the patients.

Incorporation of renal function in mortality risk assessment for pulmonary arterial hypertension.

BACKGROUND: Risk assessment is important for prognostication and individualized treatment decisions for patients with pulmonary arterial hypertension (PAH). The purpose was (1) to compare contemporary risk assessment tools and (2) to determine the prognostic significance of risk parameters of kidney function and whether they can further improve risk prediction for patients with PAH. METHODS: We identified a cohort of treatment-naive patients (n = 211) who received an incident diagnosis of PAH at the University of Ottawa Heart Institute. Using demographics, disease characteristics, and hemodynamic data at diagnosis, we categorized patients as low, intermediate, or high risk according to current European guidelines (European Society of Cardiology [ESC]) and registry to evaluate early and long-term pulmonary arterial hypertension disease management (REVEAL) risk scores. The primary end-point was transplant-free survival (TFS). RESULTS: Patients were predominantly women (64.6%) with World Health Organization function Class III symptoms (66.5%). The median TFS was 7.09 years. There was little agreement between ESC- and REVEAL-based risk estimates (weighted kappa = 0.21-0.34). Although both the ESC (log-rank, p = 0.0002) and REVEAL algorithms stratified TFS risk (p < 0.0001), the REVEAL score provided superior discrimination (C-statistic = 0.70 vs 0.59, p = 0.004). Renal function at diagnosis (p < 0.0001) and Δ renal function at 6 months (p < 0.0001) were identified as novel risk parameters and served to reclassify some patients in the intermediate-risk category to a lower or higher risk stratum (p < 0.0001). CONCLUSION: REVEAL-based strategies provide superior TFS risk discrimination to ESC/European Respiratory Society-based approaches. However, the classification of intermediate-risk patients varied significantly across tools. We demonstrate the importance of renal function, which further improved the stratification of risk in patients with PAH, particularly in patients who are considered intermediate risk.

Risk assessment in pulmonary arterial hypertension: Insights from the GRIPHON study.

BACKGROUND: Approaches to risk assessment in pulmonary arterial hypertension (PAH) include the noninvasive French risk assessment approach (number of low-risk criteria based on the European Society of Cardiology and European Respiratory Society guidelines) and Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL) 2.0 risk calculator. The prognostic and predictive value of these methods for morbidity/mortality was evaluated in the predominantly prevalent population of GRIPHON, the largest randomized controlled trial in PAH. METHODS: GRIPHON randomized 1,156 patients with PAH to selexipag or placebo. Post-hoc analyses were performed on the primary composite end-point of morbidity/mortality by the number of low-risk criteria (World Health Organization functional class I-II; 6-minute walk distance >440 m; N-terminal pro-brain natriuretic peptide <300 ng/liter) and REVEAL 2.0 risk category. Hazard ratios and 95% confidence intervals were calculated using Cox proportional hazard models. RESULTS: Both the number of low-risk criteria and the REVEAL 2.0 risk category were prognostic for morbidity/mortality at baseline and any time-point during the study. Patients with 3 low-risk criteria at baseline had a 94% reduced risk of morbidity/mortality compared to patients with 0 low-risk criteria and were all categorized as low-risk by REVEAL 2.0. The treatment effect of selexipag on morbidity/mortality was consistent irrespective of the number of low-risk criteria or the REVEAL 2.0 risk category at any time-point during the study. Selexipag-treated patients were more likely to increase their number of low-risk criteria from baseline to week 26 than placebo-treated patients (odds ratio 1.69, p = 0.0002); similar results were observed for REVEAL 2.0 risk score. CONCLUSIONS: These results support the association between risk profile and long-term outcome and suggest that selexipag treatment may improve risk profile.

Six-Minute Walk Test: Clinical Role, Technique, Coding, and Reimbursement.

The 6-min walk test (6MWT) is a commonly used test for the objective assessment of functional exercise capacity for the management of patients with moderate-to-severe pulmonary disease. Unlike pulmonary function testing, the 6MWT captures the often coexisting extrapulmonary manifestations of chronic respiratory disease, including cardiovascular disease, frailty, sarcopenia, and cancer. In contrast with cardiopulmonary exercise stress testing, this test does not require complex equipment or technical expertise. In this low complexity, safe test, the patient is asked to walk as far as possible along a 30-m minimally trafficked corridor for a period of 6 min with the primary outcome measure being the 6-min walk distance (6MWD) measured in meters. There has been interest in other derived indexes, such as distance-desaturation product (the product of nadir oxygen saturation and walk distance), which in small studies has been predictive of morbidity and mortality in certain chronic respiratory conditions. Special attention to methodology is required to produce reliable and reproducible results. Factors that can affect walk distance include track layout (continuous vs straight), track length, oxygen amount and portability, learning effect, and verbal encouragement. The absolute 6MWD and change in 6MWD are predictive of morbidity and mortality in patients with COPD, pulmonary arterial hypertension, and idiopathic pulmonary fibrosis and patients awaiting lung transplant, highlighting its use in management decisions and clinical trials. As of January 2018, Current Procedural Terminology code 94620 (simple pulmonary stress test) has been deleted and replaced by two new codes, 94617 and 94618. Code 94617 includes exercise test for bronchospasm including pre- and postspirometry, ECG recordings, and pulse oximetry. Code 94618, pulmonary stress testing (eg, 6MWT), includes the measurement of heart rate, oximetry, and oxygen titration when performed. If 94620 is billed after January 2018 it will not be reimbursed.

The importance of right ventricular evaluation in risk assessment and therapeutic strategies: Raising the bar in pulmonary arterial hypertension.

Pulmonary arterial hypertension is an obstructive pulmonary vasculopathy that leads to increased pulmonary vascular resistance, right ventricular overload and failure, and death. Patients' clinical status and prognosis depend mostly on the capability of the right ventricle to adapt to the increased afterload, maintain function, and preserve cardiac output. As a result, reducing the hemodynamic burden of the right ventricle should be a key target of current treatments, along with improvement in WHO functional class, 6-minute walk distance, and rates of hospitalization. However, physicians still find it challenging to integrate the evaluation of right ventricular function into widely accepted clinical parameters in order to stratify patients more accurately. This limitation is very relevant, since higher-risk patients are more likely to benefit from a more aggressive therapeutic approach. We analyzed the hemodynamic burden in pulmonary arterial hypertension, the importance of echocardiographic evaluation of the right ventricle, the impact of current treatments on hemodynamic parameters, and the identification of patients who are more likely to benefit from a more aggressive therapeutic approach.

Invasive Hemodynamic Assessment for the Right Ventricular System and Hypoxia-Induced Pulmonary Arterial Hypertension in Mice.

Pulmonary arterial hypertension (PAH) is a chronic and severe cardiopulmonary disorder. Mice are a popular animal model used to mimic this disease. However, the evaluation of right ventricular pressure (RVP) and pulmonary artery pressure (PAP) remains technically challenging in mice. RVP and PAP are more difficult to measure than left ventricular pressure because of the anatomical differences between the left and right heart systems. In this paper, we describe a stable right heart hemodynamic measurement method and its validation using healthy and PAH mice. This method is based on open-chest surgery and mechanical ventilation support. It is a complicated procedure compared to closed chest procedures. While a well-trained surgeon is required for this surgery, the advantage of this procedure is that it can generate both RVP and PAP parameters at the same time, so it is a preferable procedure for the evaluation of PAH models.

Echocardiographic Assessment of Right Ventricular Function and Response to Therapy in Pulmonary Arterial Hypertension.

Echocardiography is a key tool in the management of patients with pulmonary arterial hypertension (PAH), but many potential parameters could be used to assess response to therapy. In this retrospective study of 48 patients with severe PAH at baseline, we examined echocardiographic variables before and after initiation of PAH-specific therapy to evaluate which measures of right ventricular (RV) function best correlated with clinical response to therapy as assessed by 6-minute walk distance (6MWD) and 3-year all-cause mortality. Tricuspid annular plane systolic excursion (TAPSE), mid-RV and basal-RV diameters, RV systolic pressure, and RV global longitudinal strain were all found to significantly improve after initiation of a PAH therapy. Decreases in right atrial area (r = -0.50, p = 0.002) and mid-RV diameter (r = -0.36, p = 0.03) were most strongly correlated with improvement in 6MWD. Pretreatment values of RA area (hazard ratio [HR] per 1 SD: 2.72; 95% confidence interval [CI] 1.58, 4.69), mid-RV diameter (HR 2.03; 1.20, 3.45), basal-RV diameter (HR 2.27; 1.40, 3.70), and RV global longitudinal strain (HR 2.36; 1.22, 4.56) were all associated with mortality risk. 6MWD and TAPSE were the 2 variables for which pretreatment measures (6MWD - HR 0.35; 0.17, 0.72; TAPSE - HR 0.41; 0.21, 0.82) and change with treatment (6MWD - HR 0.26; 0.10, 0.64; TAPSE - HR 0.40; 0.21, 0.77) were both significantly associated with 3-year mortality. Change in RV systolic pressure with treatment was significantly associated with mortality (HR 2.55; 1.23, 5.28,) but pretreatment baseline had no association (HR 1.48; 0.72, 3.06). Although many echocardiographic parameters change with initiation of PAH treatment, the strong association of both baseline TAPSE and change in TAPSE with mortality supports the ongoing use of TAPSE as an important measure in the assessment of disease severity and treatment response in PAH.

Guideline implementation and early risk assessment in pulmonary arterial hypertension associated with congenital heart disease: A retrospective cohort study.

INTRODUCTION: Current guidelines emphasize that accurate risk stratification is important for patients with pulmonary arterial hypertension (PAH), however, few suggestions have been specified for PAH associated with congenital heart disease (PAH-CHD). OBJECTIVES: The aim of this study was to propose an accurate and simple system based on current guidelines for risk stratification in PAH-CHD patients during 12-month follow-up. METHODS: We reviewed 288 Chinese PAH-CHD patients between January 2014 and December 2016 in this retrospective cohort study. The low-risk criteria according to 2015 European Society of Cardiology guidelines and the adverse events (AEs) during follow-up were collected. The association between low-risk criteria and AEs was assessed with Cox regression, and a simplified risk stratification system was proposed. RESULTS: There were 105 PAH-CHD patients included in the final analysis. Twenty-nine patients had AEs defined as death, initiation of new or combined medication treatment, or re-hospitalisation because of the PAH worsening. Among the low-risk criteria, WHO/NYHA functional class, 6-minute walking distance (6MWD), NT-proBNP and SvO2 were significantly different between AE and AE-free groups. However, 6MWD (HR = 0.08, 95% CI: 0.03-0.19, P < 0.001) and NT-proBNP (HR = 0.35, 95% CI: 0.16-0.78, P = 0.01) were the only independent predictors of AEs in multivariable model. When taking them into a simplified system for risk stratification, the number of low-risk criteria at diagnosis discriminated the risk of AEs (P < 0.001). CONCLUSIONS: Among the low-risk criteria proposed by current guidelines, 6MWD and NT-proBNP predicted AEs independently for PAH-CHD patients. Simplified risk stratification system by taking these two parameters numerically provides accurate prognostic information in PAH-CHD patients.

Noninvasive Assessment of Right Ventricular Function in Patients with Pulmonary Arterial Hypertension and Left Ventricular Assist Device.

PURPOSE OF REVIEW: Right ventricular (RV) failure in patients with pulmonary arterial hypertension (PAH) and left ventricular assist device (LVAD) is associated with increased hospitalizations, worsening functional class, and poor survival. Accurate RV function assessment is essential in diagnosing RV failure, guiding therapies, and determining prognosis. Noninvasive imaging techniques provide fast and reliable quantification of RV morphology and function. RECENT FINDINGS: We review echocardiography, nuclear medicine, and cardiac magnetic resonance imaging (MRI) uses for RV function assessment in patients with PAH and LVAD. We identify current knowledge gaps in utilizing noninvasive tests to assess RV function. Echocardiography is most widely used to quantify RV function in patients with PAH and LVAD, followed by cardiac MRI for RV morphology and function measurement in PAH patients. The first-pass radionuclide angiography with radiolabeled RBC is the gold standard for calculating RV function. Gated blood pool SPECT can be an alternative as it separates the cardiac chambers well and provides accurate assessment of the RV function with high reproducibility, which is particularly useful for monitoring treatment. More research is needed to compare and validate these modalities in evaluating RV function.

Risk classification of pulmonary arterial hypertension by echocardiographic combined assessment of pulmonary vascular resistance and right ventricular function.

Which combination of clinical parameters improves the prediction of prognosis in patients with pulmonary arterial hypertension (PAH) remains unclear. We examined whether combined assessment of pulmonary vascular resistance and right ventricular function by echocardiography is useful for classifying risks in PAH. In 41 consecutive patients with PAH (mean age of 48.9 ± 17.3 years, 31 females), a 6-min walk test, pulmonary function test, and echocardiography were performed at baseline and during PAH-specific therapies. The study endpoint was defined as a composite of cardiovascular death and hospitalization for PAH and/or right ventricular failure. During a follow-up period of 9.2 ± 8.7 months, 18 patients reached the endpoint. Multivariate regression analysis showed that the ratio of tricuspid regurgitation pressure gradient to the time-velocity integral of the right ventricular outflow tract (TRPG/TVI) and tricuspid annular plane systolic excursion (TAPSE) during PAH-specific treatment were independent prognostic predictors of the endpoint. Using cutoff values indicated by receiver operating characteristic analysis, the patients were divided into four subsets. Multivariate analyses by Cox's proportional hazards model adjusted for age, sex and body mass index indicated that subset 4 (TRPG/TVI ≥ 3.89 and TAPSE ≤ 18.9 mm) had a significantly higher event risk than did subset 1 (TRPG/TVI < 3.89 and TAPSE > 18.9 mm): HR = 25.49, 95% CI 4.70-476.97, p < 0.0001. Combined assessment of TRPG/TVI and TAPSE during adequate PAH-specific therapies enables classification of risks for death and/or progressive right heart failure in PAH.

Assessment of reversibility in pulmonary arterial hypertension and congenital heart disease.

Pulmonary arterial hypertension (PAH) in congenital heart disease (CHD) can be reversed by early shunt closure, but this potential is lost beyond a certain point of no return. Therefore, it is crucial to accurately assess the reversibility of this progressive pulmonary arteriopathy in an early stage. Reversibility assessment is currently based on a combination of clinical symptoms and haemodynamic variables such as pulmonary vascular resistance. These measures, however, are of limited predictive value and leave many patients in the grey zone. This review provides a concise overview of the mechanisms involved in flow-dependent progression of PAH in CHD and evaluates existing and future alternatives to more directly investigate the stage of the pulmonary arteriopathy. Structural quantification of the pulmonary arterial tree using fractal branching algorithms, functional imaging with intravascular ultrasound, nuclear imaging, putative new blood biomarkers, genetic testing and the potential for transcriptomic analysis of circulating endothelial cells and educated platelets are being reviewed.

Quantification of biventricular strain and assessment of ventriculo-ventricular interaction in pulmonary arterial hypertension using exercise cardiac magnetic resonance imaging and myocardial feature tracking.

BACKGROUND: Right ventricular (RV) failure is the main cause of mortality in pulmonary arterial hypertension (PAH). Exercise testing helps identify early RV maladaptation and systolic dysfunction and facilitates therapy. Myocardial strain has been shown to be more sensitive than ejection fraction (EF) in detecting subclinical ventricular contractile dysfunction. Chronic pressure overload in PAH had been associated with changes in left ventricular (LV) filling. PURPOSE: To compare biventricular strains and ventriculo-ventricular interaction in PAH and controls using cardiac magnetic resonance feature tracking (cMRI-FT) and to determine the reproducibility of strain analysis. STUDY TYPE: Prospective. POPULATION: Nine PAH and nine control subjects. FIELD STRENGTH/SEQUENCE: 1.5T MRI balanced steady state free precession. ASSESSMENT: RV and LV longitudinal strain (EllRV and EllLV ) were derived using the mid-axial images. Radial (ErrLV ) and circumferential strain (EccLV ) were derived using the mid-ventricular short-axis images. Relationships between strain and volumetric parameters were assessed at rest and during submaximal in-magnet exercise. STATISTICAL TESTS: Comparison of rest-to-exercise data between PAH and controls was analyzed using two-way repeated measures analysis of variance. The relationship between volumetric parameters and cMRI-FT were assessed using Pearson's correlation. Reproducibility was assessed by using Bland-Altman plots. RESULTS: PAH had significantly lower EllRV at rest (-16.6 ± 2.7 vs. -20.1 ± 3.6, P = 0.03) despite normal RVEF. During exercise, RV systolic contractile reserve measured by EllRV was significantly reduced in PAH (PInteraction = 0.02). In PAH, indexed RV end-systolic volume (ESVi) significantly correlated with EccLV and ErrLV at rest (r = -0.65 and r = -0.70, P < 0.05) and with ErrLV during exercise (r = -0.43, P < 0.05). High observer agreement was demonstrated. DATA CONCLUSION: Despite normal resting RVEF, RV systolic function and contractile reserve as measured by EllRV was significantly reduced in PAH. The close relation between RVESVi with EccLV and ErrLV provides evidence of systolic ventriculo-ventricular interaction in PAH. Exercise cMRI-FT may provide a quantitative metric for detection of subclinical RV dysfunction in PAH. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1427-1436.