The impact of baseline right ventricular-pulmonary artery coupling on the short-term outcome after valve replacement surgery for rheumatic mitral stenosis

Introduction

Rheumatic heart disease (RHD), a severe long-term consequence of acute rheumatic fever, commonly leads to mitral valve lesions. Although mitral stenosis (MS) is prevalent in many regions, mitral regurgitation is more frequently observed in areas with limited primary prevention of rheumatic fever, such as some African countries (1). Pulmonary hypertension (PH) is one of the common complications of RHD (2); this hemodynamic disorder directly impairs right ventricular function and triggers a vicious cycle via right ventricular-pulmonary artery (RV-PA) coupling imbalance. RV-PA coupling is the dynamic equilibrium between right ventricular systolic function and pulmonary arterial afterload, reflecting the match between right ventricular energy transfer efficiency and circulatory load (3). In chronic pressure overload, RV-PA decoupling signals the right ventricle’s shift from compensatory hypertrophy to decompensated dilation, causing irreversible right heart failure progression (4). In recent years, studies have confirmed that the tricuspid annular plane systolic excursion/pulmonary artery systolic pressure (TAPSE/PASP) ratio, a non-invasive ultrasonic parameter for evaluating RV-PA coupling, is a direct substitute for invasively measured end-systolic elastance/effective arterial elastance (Ees/Ea) (5). An abnormally low TAPSE/PASP ratio is independently linked to all-cause mortality in PH patients (6).

Currently, studies link right ventricular dysfunction (RVD) and PH to post-cardiac surgery prognosis (7,8). However, the effect of preoperative RV-PA coupling on postoperative hemodynamic remodeling is unclear, and guidelines do not include it in risk assessment. The value of RV-PA coupling in risk stratification needs further verification.

This study evaluated how baseline RV-PA coupling affects early mortality and peri-operative events in rheumatic mitral stenosis (RMS) patients post-mitral valve replacement (MVR). It aimed to build a more accurate risk-stratification system, spot risks in low-risk patients, and offer evidence for optimizing MVR timing. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1380/rc).

Methods

Participants

This was a prospective observational study conducted from January 2021 to January 2024 to evaluate the impact of baseline RV-PA coupling on short-term outcomes in RMS patients undergoing MVR. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of The First Affiliated Hospital of Guangxi Medical University (No. 2022-KY-E-132) and informed consent was provided by all individual participants. Strict inclusion and exclusion criteria were applied. RMS patients aged ≥18 years, who were scheduled to undergo MVR, had measurable RV-PA coupling parameters, were tolerant to surgery, and had complete clinical and follow-up data were included. Exclusions were those with aortic valve stenosis, right ventricular outflow tract obstruction, pulmonary valve stenosis, congenital heart disease, valvular surgery history, factors affecting pulmonary artery pressure assessment, severe systemic diseases, and ineffective echocardiographic images (Figure 1).

Figure 1 Patient enrollment process. PASP, pulmonary artery systolic pressure; RMS, rheumatic mitral stenosis; TAPSE, tricuspid annular plane systolic excursion.

Echocardiographic measurement

Echocardiography was performed 3 days pre-operation. Two senior technicians followed American Society of Echocardiography guidelines, using a Philips IE33/EPIQ7C (S5-1 probe, 2.5–5.0 MHz; Philips Healthcare, Amsterdam, The Netherlands) for standard operation. RV-PA coupling was quantified by TAPSE/PASP. TAPSE was measured via M-mode in the four-chamber view as the tricuspid annulus lateral wall peak displacement. PASP was calculated using the simplified Bernoulli equation (4V² + RAP). RAP was determined by inferior vena cava (IVC) diameter and inspiratory collapse rate (IVC ≤21 mm with >50% collapse: 3 mmHg; IVC >21 mm with <50% collapse: 15 mmHg; critical value: 8 mmHg) (9). Continuous electrocardiogram (ECG) monitoring was conducted, and 3–5 cardiac cycles were collected from all patients. For the measurement of right ventricular end-diastolic area (RVEDA) and right ventricular end-systolic area (RVESA), two-dimensional echocardiography with the apical four-chamber view was employed. At end-diastole (onset of the QRS complex on the ECG) for RVEDA, and at end-systole (peak of the T wave on the ECG) for RVESA, the endocardial border of the right ventricle was manually traced, excluding trabeculations and papillary muscles, to ensure accurate area measurement and enhance result reproducibility and interpretability (Figure 2).

Figure 2 Echocardiographic measurements for assessing RV-PA coupling and right ventricular function. (A) CW Doppler echocardiogram showing measurement of tricuspid regurgitation peak velocity. (B) M-mode echocardiogram demonstrating measurement of TAPSE. (C) Echocardiographic view showing the RVEDA. (D) Echocardiographic view showing the RVESA for calculating RVFAC. CW, continuous-wave; TAPSE, tricuspid annular plane systolic excursion; RVEDA, right ventricular end-diastolic area; RVESA, right ventricular end-systolic area; RVFAC, right ventricular fractional area change; RV-PA, right ventricular-pulmonary artery.

Definition of research endpoints

The primary outcome was 90-day post-surgery all-cause mortality. This follow-up duration was chosen for the following reasons: (I) patients after MVR may experience delayed complications, infection, cardiac function deterioration between 30 and 90 days post-surgery, and limiting the endpoint to 30 days or in-hospital mortality may miss important prognostic information; (II) a 90-day period covers the critical stage from the acute postoperative phase to the recovery phase, which is more in line with the clinical assessment of “short-term prognosis” and can comprehensively reflect the impact of baseline RV-PA coupling on postoperative outcomes. Secondary outcomes were perioperative adverse events: prolonged mechanical ventilation (>48 h), postoperative bleeding requiring re-thoracotomy, malignant arrhythmias, myocardial infarction, cardiogenic shock, low cardiac output syndrome, cardiac surgery-associated acute kidney injury; kidney disease: improving global outcomes (CSA-AKI; KDIGO stands for Kidney Disease: Improving Global Outcomes. criteria: ≥50% or ≥2-fold serum creatinine increase within 7 days post-surgery or renal replacement therapy needed), new-onset stroke, multiple organ dysfunction syndrome (MODS), and unplanned intensive care unit (ICU) readmission.

Statistical analysis

This study used the software SPSS 27.0 (IBM Corp., Armonk, NY, USA) and R 4.4.3 (R Foundation for Statistical Computing, Vienna, Austria) for statistical analysis. Shapiro-Wilk test was used to evaluate data normality. Normal data were presented as mean ± standard deviation (SD), non-normal as median [interquartile range (IQR)], and count data as frequency (%). Based on TAPSE/PASP, the cohort was divided into high/low coupling groups. The t-test/Mann-Whitney U test (continuous variables) and Pearson χ²/Fisher’s exact test (categorical variables) were used to compare groups. Cox models were used to identify death risk predictors. The Kaplan-Meier method was used to plot survival curves and log-rank testing was conducted. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic performance of indicators including TAPSE/PASP, TAPSE, PASP, and N-terminal pro-B-type natriuretic peptide (NT-proBNP) for predicting 90-day mortality. The optimal cut-off value of the TAPSE/PASP ratio was determined based on the Youden index (sensitivity + specificity − 1) to maximize the discriminative ability for 90-day mortality. After excluding patients with tricuspid regurgitation (TR) ≥3, sensitivity analysis was conducted. Integrated discrimination improvement (IDI) and continuous net reclassification improvement (NRI) were used to compare TAPSE, PASP, and TAPSE/PASP with the basic model. A P value <0.05 (two-sided) was considered statistically significant.

Reproducibility of right heart parameter measurement

Echocardiographic images of 30 randomly selected patients were used. Two experienced attending physicians measured these images twice at different time points. Collected data underwent an intraclass correlation coefficient (ICC) testing for within-and between-observer reliability analysis.

Results

Baseline data

Table 1 summarizes the baseline characteristics of the 286-patient study cohort with RMS (mean age 53.8±8.78 years, 75.9% female), defined by mitral valve area (MVA) ≤1.5 cm² (57.3% with MVA <1.0 cm²). A total of 219 participants (76.6%) had atrial fibrillation history, and 42 (14.6%) had a stroke history. Patients with impaired RV-PA coupling had a higher proportion of MVA <1.0 cm² (73.2% vs. 47.1%, P<0.001), higher surgical risk [European System for Cardiac Operative Risk Evaluation II (EuroSCORE II): 3.0 vs. 2.6, P=0.025], worse cardiac function [New York Heart Association (NYHA) IV: 19.6% vs. 9.8%, P=0.004], and elevated biomarkers such as NT-proBNP (median: 2,307.5 vs. 1,024.0 pg/mL, P<0.001), creatinine (81.6 vs. 77.5 µmol/L, P=0.036), and aspartate aminotransferase (ASAT; median: 30.0 vs. 24.5 U/L, P<0.001).

RV-PA coupling features

ROC curve analysis evaluated the predictive performance of indicators including TAPSE/PASP, TAPSE, PASP, and NT-proBNP for 90-day mortality (Figure 3); the area under the curve (AUC) of TAPSE/PASP was the highest (0.745). An AUC >0.7 suggested moderate predictive power of TAPSE/PASP. The optimal TAPSE/PASP cut-off for 90-day mortality prediction was 0.32 mm/mmHg (average: 0.4±0.20 mm/mmHg). Using this cut-off, 112 patients (39.2%, TAPSE/PASP ≤0.32 mm/mmHg) were classified as having RVD, whereas 174 patients (60.8%, TAPSE/PASP >0.32 mm/mmHg) had preserved RV-PA coupling.

Figure 3 ROC curve analysis of diagnostic efficacy for various indicators. The x-axis represents 100% specificity, and the y-axis denotes sensitivity. AUC, area under the curve; NT-proBNP, N-terminal pro-B natriuretic peptide; ROC, receiver operating characteristic; TAPSE/PASP, tricuspid annular plane systolic excursion/pulmonary artery systolic pressure.

Baseline echocardiographic parameters

As shown in Table 2, compared with the group with preserved coupling, patients with impaired RV-PA coupling showed obvious biventricular dysfunction. Left ventricular parameters included an increase in the left atrial diameter (LAD; 58.5 vs. 52.2 mm, P<0.001) and an elevation in the mitral E/e’ ratio (58.0 vs. 51.1, P<0.001), and a decrease in the left ventricular ejection fraction (LVEF; 62.0% vs. 64.0%, P=0.046). Right ventricular function was significantly impaired, with a decrease in TAPSE (14.5 vs. 18.5 mm, P<0.001), a reduction in systolic tissue velocity (S’: 9.8 vs. 12.0 cm/s, P<0.001), a decrease in the fractional area change (FAC; 29.6% vs. 37.3%, P<0.001), an elevation in the tricuspid E/e’ ratio (3.5 vs. 3.2, P<0.001), and pulmonary artery hemodynamics showed an increase in PASP (65.8 vs. 37.8 mmHg, P<0.001). Right heart remodeling included right atrial enlargement [right atrial area/body surface area (RAA/BSA): median 14.1 vs. 10.7 cm²/m²] and ventricular dimensions (RVEDA/BSA: 14.8 vs. 12.1 cm²/m², P<0.001). Meanwhile, the incidences of moderate/severe TR were 26.8% vs. 9.2%; 25.0% vs. 2.9%, larger IVC diameter, and a higher pulmonary embolism incidence compared to the group with preserved coupling.

Surgical situations and early outcomes

Table 3 shows the surgical details and postoperative outcomes of two patient groups. All 286 had MVR: 178 (62.2%) with mechanical valves, 108 (38.8%) with biological ones. Regarding intraoperative variables, the impaired group had a significantly higher rate of concomitant tricuspid valve repair (49.1% vs. 20.1%, P<0.001), and mechanical valves were more commonly used in this group (73.2% vs. 55.2%, P=0.004). Although operative duration, aortic cross-clamp time, and cardiopulmonary bypass time did not differ significantly, the length of ICU stay was notably longer in the TAPSE/PASP ≤0.32 group (55.4 vs. 40.0 h, P=0.016). For short-term outcomes, the impaired group showed a significantly higher 90-day mortality (16.1% vs. 2.9%, P<0.001) and overall perioperative adverse event rate (41.1% vs. 17.8%, P<0.001). Specifically, incidences of prolonged invasive ventilation (>48 h, 25.9% vs. 13.2%, P=0.007), cardiogenic shock (13.4% vs. 2.3%, P<0.001), acute heart failure (8.2% vs. 0.7%, P<0.001), and arrhythmia (12.5% vs. 1.7%, P<0.001) were significantly elevated in the impaired group, whereas no significant between-group differences were observed in complications such as cardiac tamponade, low cardiac output syndrome, re-exploration, ICU readmission, CSA-AKI, or MODS (all P>0.05).

Association between TAPSE/PASP and patient prognosis

The Kaplan-Meier analysis showed that the patients with impaired RV-PA coupling had a significantly lower 90-day survival rate than those with preserved coupling (log-rank P<0.001). Among patients with mild PH (PASP <50 mmHg, n=183) (Figure 4), survival rates differed significantly between the impaired and preserved coupling subgroups (log-rank P<0.001), but no such difference was seen in moderate/severe PH subgroups (PASP ≥50 mmHg, n=103) (log-rank P=0.291). Among patients with preserved coupling, there was no significant survival difference between those with mild and moderate/severe PH (log-rank P=0.649).

Figure 4 Kaplan-Meier survival curves stratified by TAPSE/PASP ratio. (A) Survival probabilities in patients with PH Class I, stratified by TAPSE/PASP >0.32 mm/mmHg (blue line) and TAPSE/PASP ≤0.32 mm/mmHg (orange line). (B) Survival probabilities in the overall study population (including patients with mild, moderate, and severe PH), stratified by TAPSE/PASP >0.32 mm/mmHg (blue line) and TAPSE/PASP ≤0.32 mm/mmHg (orange line). Log-rank test P<0.001 for both panels. Numbers at risk are shown below each curve. PH, pulmonary hypertension; TAPSE/PASP, tricuspid annular plane systolic excursion/pulmonary artery systolic pressure.

Cox regression analysis identified 90-day mortality predictors in univariate and multivariate models (Table 4). Univariate analysis showed that low TAPSE/PASP and NYHA class IV were associated with 90-day mortality (P<0.001). Multivariate analysis indicated that they remained independent risk factors (P=0.004, P=0.002). Low TAPSE/PASP patients undergoing surgery had secondary composite outcomes (postoperative adverse events) [hazard ratio (HR) =2.7; 95% confidence interval (CI): 1.46–5.00; P=0.001].

To address PASP estimation inaccuracy in severe TR, we excluded patients with TR ≥3 and performed a sensitivity analysis on 253 patients, validating the negative impact of low baseline TAPSE/PASP on MVR outcomes. IDI and continuous NRI analyses showed adding TAPSE and TAPSE/PASP to the basic model improved event discrimination and risk reclassification, whereas adding PASP did not. Considering both IDI and continuous NRI, adding TAPSE/PASP to the basic model was best for event discrimination and risk reclassification (Table 5).

Discussion

The main findings were as follows: (I) approximately 39.2% of the participants who underwent MVR had preoperative RV-PA decoupling (RVD); (II) the Kaplan-Meier analysis showed that the RVD patients had a poor survival rate, and the coupling status was related to the survival rate in patients with mild PH; (III) low TAPSE/PASP independently predicts short-term adverse MVR outcomes.

A low TAPSE/PASP ratio indicates RV-PA decoupling and right ventricular maladaptation (6,7); it may emerge in the late adaptive stage of PH from valvular heart disease and is an important prognostic factor (10). In RHD, prior studies mainly evaluated isolated right ventricular function or the impact of PH on prognosis (7,8,11,12). However, evidence on how baseline RV-PA coupling affects the short-term prognosis of RMS patients is lacking, and further research is needed to validate its clinical value.

In this study, the incidence of preoperative RV-PA decoupling in RMS patients with PH may be due to RMS-related PH pathology. In RMS, PH results from both increased left-atrial pressure and elevated pulmonary vascular resistance from vasoconstriction and remodeling (13). Long-term pressure overload causes RVD (4).

The RVD patients had a significantly higher 90-day postoperative mortality, linked to more right heart failure complications such as cardiogenic shock and acute heart failure. The cohort’s 8.0% mortality was in line with previous reports (5–12%) (8,11,12,14), showing controllable surgical risk. However, the low RV-PA coupling group’s 90-day mortality (16.1%) was much higher than that in the high RV-PA coupling group’s (2.9%). We hypothesize that differences stem from the surgery correcting left atrial hypertension eases pulmonary venous congestion, potentially dropping pulmonary artery pressure and RV afterload suddenly. Patients with high baseline RV-PA coupling, having well-preserved ventricular and right heart function plus afterload reserve, can adapt to pressure changes, maintaining or boosting cardiac output as afterload lessens. Conversely, in those with long-term RV adaptation to high afterload, a sudden pressure drop may cause acute right ventricular dilation and wall-tension increase, leading to myocardial oxygen imbalance. Via ventricular interdependence, this reduces left ventricular diastolic compliance, cutting cardiac output and blood pressure, and quickly triggering cardiogenic shock and death, in line with Brener et al.’s (15) “afterload reserve” concept. Moreover, the low-coupling group, having weaker right heart structure and function, needs more tricuspid repairs and longer ventilation. This increases inflammation and hemodynamic instability risks.

We also discovered that the RV-PA coupling status significantly influenced the survival rate in the mild PH group, yet had no marked effect in the moderate and severe PH groups. We surmise this could be because, during the mild PH stage, the RV sustains adaptive remodeling. Myocardial fibers are circumferentially arranged and collagen fibers are in a relaxed state, allowing the RV-PA coupling to effectively differentiate compensatory capacity differences and serve as a crucial survival-rate predictor. In contrast, in moderate and severe PH, long-term high load causes the right ventricle to undergo pathological remodeling. Myocardial fibers arrange longitudinally and collagen-fiber tension increases substantially, resulting in RV stiffness and loss of anisotropy (16). At this point, the survival rate might be more determined by end-stage pathologies such as pulmonary vascular remodeling, right heart failure, and multiple organ dysfunction. It could also be attributed to the small sample size or limited survival events in the moderate and severe PH groups of this study; future research should increase the sample size. This difference indicates the significance of early intervention on RV-PA coupling during mild PH.

International guidelines differ in defining MS severity. The American College of Cardiology/American Heart Association (ACC/AHA) deems an orifice area ≤1.5 cm² “severe” (17), whereas the European Society of Cardiology/European Association for Cardio-Thoracic Surgery (ESC/EACTS) and Japan label it “moderate” (18,19), leading to inconsistent surgical timing. Our study indicates that, regardless of MS classification, assessing the preoperative TAPSE/PASP ratio and hemodynamic parameters should drive surgical decisions. Future multicenter studies are needed to confirm the TAPSE/PASP ratio’s role in RMS risk-stratification and explore its synergy with PH treatment or surgical timing.

This study provides a new perioperative management framework for rheumatic MS. The RV-PA coupling status, which indicates disease severity and guides intervention strategies, should be part of preoperative assessments. This is especially crucial for often-overlooked patients with mild PH.

Limitations

This study has several limitations. Methodologically, it lacks validation using invasive hemodynamic data. At the measurement stage, TAPSE/PASP is affected by various factors, prone to causing PASP assessment deviations. In terms of the sample, the small, single-center sample size makes it hard to fully explore disease heterogeneity and pathological mechanisms. Post-operative assessment is also insufficient, as RV-PA coupling changes were not analyzed. The prediction model is rather simple; a comprehensive one should be built by integrating multiple parameters to better evaluate prognosis.

Conclusions

As indicated by RV-PA coupling impairment, RVD is a significant predictor of increased mortality in RMS patients undergoing MVR. Thus, when planning MVR for severe RMS, RV parameters such as RV dilation and RV-PA coupling should be systematically evaluated.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1380/rc

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1380/dss

Funding: This study was funded by the Key Program of Guangxi Natural Science Foundation (grant No. 2022JJD140147), the National Clinical Key Specialty Construction Project of China (Department of Cardiovascular Surgery, The First Affiliated Hospital of Guangxi Medical University), and the Clinical Key Specialty Construction Project of Guangxi (Department of Cardiothoracic Surgery, The First Affiliated Hospital of Guangxi Medical University).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1380/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of The First Affiliated Hospital of Guangxi Medical University (No. 2022-KY-E-132) and informed consent was obtained from all individual participants.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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(English Language Editor: J. Jones)