Single-Beat Estimation of Right Ventricular Contractility and Its Coupling to Pulmonary Arterial Load in Patients With Pulmonary Hypertension

Clinical Usefulness of Right Ventricle-Pulmonary Artery Coupling in Cardiovascular Disease

Right ventricular-pulmonary artery coupling (RV-PA coupling) refers to the relationship between RV contractility and RV afterload. Normal RV-PA coupling is maintained only when RV function and pulmonary vascular resistance are appropriately matched. RV-PA uncoupling occurs when RV contractility cannot increase to match RV afterload, resulting in RV dysfunction and right heart failure. RV-PA coupling plays an important role in the pathophysiology and progression of cardiovascular diseases. Therefore, early and accurate evaluation of RV-PA coupling is of great significance for a patient's condition assessment, clinical decision making, risk stratification, and prognosis judgment. RV-PA coupling can be assessed by using invasive or noninvasive approaches. The aim of this review was to summarize the pathological mechanism and evaluation methods of RV-PA coupling, the advantages and disadvantages of each method, and the application value of RV-PA coupling in various cardiovascular diseases.

Right Ventricular Energy Failure Predicts Mortality in Patients With Pulmonary Hypertension

Right ventricular (RV) failure has a significant adverse impact on pulmonary hypertension (PH) prognosis. None of the currently used parameters directly assess whether RV fails to provide enough energy output to propel the blood through diseased pulmonary vascular system. Furthermore, most of the current parameters are affected by the volume status of the patient. We aimed to explore whether RV energy failure has a predictive power for mortality on top of the established prognostic risk parameters in patients with PH. We screened 723 cases from our database. A total of 3 sets of binary regression analyses were executed to determine the hazard ratios (HRs) of RV energy failure for 5-year mortality in clinical, echocardiographic, and hemodynamic context, using adjustment variables chosen according to previous studies. The final study population encompassed 549 cases. A total of 77 patients died during the 5-year follow-up (14%). RV energy failure was observed in 146 of 549 patients (26.6%). In the univariate model, RV energy failure strongly associated with increased long-term mortality (HR 4.25, 95% confidence interval [CI] 2.58 to 7.00, p <0.001). It also emerged as a significant predictor of long-term mortality in clinical and hemodynamic multivariate models (HR 2.59, 95% CI 1.43 to 4.67, p = 0.002 and HR 2.05, 95% CI 1.15 to 3.63, p = 0.015, respectively). In conclusion, our study indicates that the presence of RV energy failure independently predicts long-term mortality in PH.

Pressure Volume Loop Analysis of the Right Ventricle in Heart Failure With Computed Tomography

Right ventricular (RV) function is an important marker of mortality in chronic left-sided heart failure. Right ventricular function is particularly important for patients receiving left ventricular assist devices as it is a predictor of postoperative RV failure. RV stroke work index (RVSWI), the area enclosed by a pressure-volume (PV) loop, is prognostic of RV failure. However, clinical RVSWI approximates RVSWI as the product of thermodilution-derived stroke volume and the pulmonary pressure gradient. This ignores the energetic contribution of regurgitant flow and does not allow for advanced energetic measures, such as pressure-volume area and efficiency. Estimating RVSWI from forward flow may underestimate the underlying RV function. We created single-beat PV loops by combining data from cine computed tomography (CT) and right heart catheterization in 44 heart failure patients, tested the approximations made by clinical RVSWI and found it to underestimate PV loop RVSWI, primarily due to regurgitant flow in tricuspid regurgitation. The ability of RVSWI to predict post-operative RV failure improved when the single-beat approach was used. Further, RV pressure-volume area and efficiency measures were obtained and show broad agreement with other functional measures. Future work is needed to investigate the utility of these PV metrics in a clinical setting.

Adaptive versus maladaptive right ventricular remodelling

Right ventricular (RV) function and its adaptation to increased afterload [RV-pulmonary arterial (PA) coupling] are crucial in various types of pulmonary hypertension, determining symptomatology and outcome. In the course of disease progression and increasing afterload, the right ventricle undergoes adaptive remodelling to maintain right-sided cardiac output by increasing contractility. Exhaustion of compensatory RV remodelling (RV-PA uncoupling) finally leads to maladaptation and increase of cardiac volumes, resulting in heart failure. The gold-standard measurement of RV-PA coupling is the ratio of contractility [end-systolic elastance (Ees)] to afterload [arterial elastance (Ea)] derived from RV pressure-volume loops obtained by conductance catheterization. The optimal Ees/Ea ratio is between 1.5 and 2.0. RV-PA coupling in pulmonary hypertension has considerable reserve; the Ees/Ea threshold at which uncoupling occurs is estimated to be ~0.7. As RV conductance catheterization is invasive, complex, and not widely available, multiple non-invasive echocardiographic surrogates for Ees/Ea have been investigated. One of the first described and best validated surrogates is the ratio of tricuspid annular plane systolic excursion to estimated pulmonary arterial systolic pressure (TAPSE/PASP), which has shown prognostic relevance in left-sided heart failure and precapillary pulmonary hypertension. Other RV-PA coupling surrogates have been formed by replacing TAPSE with different echocardiographic measures of RV contractility, such as peak systolic tissue velocity of the lateral tricuspid annulus (S'), RV fractional area change, speckle tracking-based RV free wall longitudinal strain and global longitudinal strain, and three-dimensional RV ejection fraction. PASP-independent surrogates have also been studied, including the ratios S'/RV end-systolic area index, RV area change/RV end-systolic area, and stroke volume/end-systolic volume. Limitations of these non-invasive surrogates include the influence of severe tricuspid regurgitation (which can cause distortion of longitudinal measurements and underestimation of PASP) and the angle dependence of TAPSE and PASP. Detection of early RV remodelling may require isolated analysis of single components of RV shortening along the radial and anteroposterior axes as well as the longitudinal axis. Multiple non-invasive methods may need to be applied depending on the level of RV dysfunction. This review explains the mechanisms of RV (mal)adaptation to its load, describes the invasive assessment of RV-PA coupling, and provides an overview of studies of non-invasive surrogate parameters, highlighting recently published works in this field. Further large-scale prospective studies including gold-standard validation are needed, as most studies to date had a retrospective, single-centre design with a small number of participants, and validation against gold-standard Ees/Ea was rarely performed.

Left atrial conduit flow rate at baseline and during exercise: an index of impaired relaxation in HFpEF patients

Aims

In healthy subjects, adrenergic stimulation augments left ventricular (LV) long‐axis shortening and lengthening, and increases left atrial (LA) to LV intracavitary pressure gradients in early diastole. Lower increments are observed in patients with heart failure with preserved ejection fraction (HFpEF). We hypothesized that exercise in HFpEF would further impair passive LV filling in early‐mid diastole, during conduit flow from pulmonary veins.

Methods and results

Twenty HFpEF patients (67.8 ± 9.8 years; 11 women), diagnosed using 2007 ESC recommendations, underwent ramped semi‐supine bicycle exercise to submaximal target heart rate (∼100 bpm) or symptoms. Seventeen asymptomatic subjects (64.3 ± 8.9 years; 7 women) were controls. Simultaneous LA and LV volumes were measured from pyramidal 3D‐echocardiographic full‐volume datasets acquired from an apical window at baseline and during stress, together with brachial arterial pressure. LA conduit flow was computed from the increase in LV volume from its minimum at end‐systole to the last frame before atrial contraction (onset of the P wave), minus the reduction in LA volume during the same time interval; the difference was integrated and expressed as average flow rate, according to a published formula. The slope of single‐beat preload recruitable stroke work (PRSW) quantified LV inotropic state. 3D LV torsion (rotation of the apex minus rotation of the base divided by LV length) was also measurable, both at rest and during stress, in 10 HFpEF patients and 4 controls. There were divergent responses in conduit flow rate, which increased by 40% during exercise in controls (+17.8 ± 37.3 mL/s) but decreased by 18% in patients with HFpEF (−9.6 ± 42.3 mL/s) (P = 0.046), along with congruent changes (+1.77 ± 1.13°/cm vs. −1.94 ± 2.73°/cm) in apical torsion (P = 0.032). Increments of conduit flow rate and apical torsion during stress correlated with changes in PRSW slope (P = 0.003 and P = 0.006, respectively).

Conclusions

In HFpEF, conduit flow rate decreases when diastolic dysfunction develops during exercise, in parallel with changes in LV inotropic state and torsion, contributing to impaired stroke volume reserve. Conduit flow is measurable using 3D‐echocardiographic full‐volume atrio‐ventricular datasets, and as a marker of LV relaxation can contribute to the diagnosis of HFpEF.

Right Ventricular Function and Its Coupling With Pulmonary Circulation in Precapillary Pulmonary Hypertension: A Three-Dimensional Echocardiographic Study

Objective: To assess right ventricular (RV) function and RV-pulmonary arterial (PA) coupling by three-dimensions echocardiography and investigate the ability of RV-PA coupling to predict adverse clinical outcomes in patients with precapillary pulmonary hypertension (PH). Methods: We retrospectively collected a longitudinal cohort of 203 consecutive precapillary PH patients. RV volume, RV ejection fraction (RVEF), and RV longitudinal strain (RVLS) were quantitatively determined offline by 3D echocardiography. RV-PA coupling parameters including the RVEF/PA systolic pressure (PASP) ratio, pulmonary arterial compliance (PAC), and total pulmonary resistance (TPR) were recorded. Results: Over a median follow-up period of 20.9 months (interquartile range, 0.1-67.4 months), 87 (42.9%) of 203 patients experienced adverse clinical outcomes. With increasing World Health Organization functional class (WHO-FC), significant trends were observed in increasing RV volume, decreasing RVEF, and worsening RVLS. RV arterial coupling (RVAC) and PAC were lower and TPR was higher for WHO-FC III+IV than WHO-FC I or II. The RVEF/PASP ratio showed a significant correlation with RVLS. RVAC had a stronger correlation with the RVEF/PASP ratio than other indices. Multivariate Cox proportional-hazard analysis identified a lower 3D RVEF and worse RVLS as strong predictors of adverse clinical events. RVAC, TPR, and PAC had varying degrees of predictive value, with optimal cutoff values of 0.74, 11.64, and 1.18, respectively. Conclusions: Precapillary-PH with RV-PA uncoupling as expressed by a RVEF/PASP ratio <0.44 was associated with adverse clinical outcomes. PAC decreased and TPR increased with increasing WHO-FC, with TPR showing better independent predictive value.

Cardiac Magnetic Resonance Imaging in Pulmonary Arterial Hypertension: Ready for Clinical Practice and Guidelines?

Purpose of Review

Pulmonary arterial hypertension (PAH) is a progressive disease with high mortality. A greater understanding of the physiology and function of the cardiovascular system in PAH will help improve survival. This review covers the latest advances within cardiovascular magnetic resonance imaging (CMR) regarding diagnosis, evaluation of treatment, and prognostication of patients with PAH.

Recent Findings

New CMR measures that have been proven relevant in PAH include measures of ventricular and atrial volumes and function, tissue characterization, pulmonary artery velocities, and arterio-ventricular coupling.

Summary

CMR markers carry prognostic information relevant for clinical care such as treatment response and thereby can affect survival. Future research should investigate if CMR, as a non-invasive method, can improve existing measures or even provide new and better measures in the diagnosis, evaluation of treatment, and determination of prognosis of PAH.

Understanding ventriculo-arterial coupling

In the late 19th century, Otto Frank published the first description of a ventricular pressure-volume diagram, thus laid the foundation for modern cardiovascular physiology. Since then, the analysis of the pressure-volume loops became a reference tool for the study of the ventricular pump properties. However, understanding cardiovascular performance requires both the evaluation of ventricular properties and the modulating effects of the arterial system, since the heart and the arterial tree are anatomically and functionally related structures. The study of the coupling between the cardiac function and the properties of the arterial system, or ventriculo-arterial (VA) coupling, provides then a comprehensive characterization of the performance of the cardiovascular system in both health and disease. The assessment of cardiovascular function is an essential element of the hemodynamic evaluation of critically ill patients. Both left and right ventricular dysfunction and arterial system disturbances are frequent in these patients. Since VA coupling ultimately defines de performance and efficiency of the cardiovascular system, the analysis of the interaction between the heart and the arterial system could offer a broader perspective of the hemodynamic disorders associated with common conditions, such as septic shock, heart failure, or right ventricular dysfunction. Moreover, this analysis could also provide valuable information about their pathophysiological mechanisms and may help to determine the best therapeutic strategy to correct them. In this review, we will describe the basic principles of the VA coupling assessment, its limitations, and the most common methods for its estimation at the bedside. Then, we will summarize the current knowledge of the application of VA coupling in critically ill patients and suggest some recommendations for further research.

Multi-Beat Right Ventricular-Arterial Coupling Predicts Clinical Worsening in Pulmonary Arterial Hypertension

Background Although right ventricular (RV) to pulmonary arterial (RV-PA) coupling is considered the gold standard in assessing RV dysfunction, its ability to predict clinically significant outcomes is poorly understood. We assessed the ability of RV-PA coupling, determined by the ratio of multi-beat (MB) end-systolic elastance (Ees) to effective arterial elastance (Ea), to predict clinical outcomes. Methods and Results Twenty-six subjects with pulmonary arterial hypertension (PAH) underwent same-day cardiac magnetic resonance imaging, right heart catheterization, and RV pressure-volume assessment with MB determination of Ees/Ea. RV ejection fraction (RVEF), stroke volume/end-systolic volume, and single beat-estimated Ees/Ea were also determined. Patients were treated with standard therapies and followed prospectively until they met criteria of clinical worsening (CW), as defined by ≥10% decline in 6-minute walk distance, worsening World Health Organization (WHO) functional class, PAH therapy escalation, RV failure hospitalization, or transplant/death. Subjects were 57±14 years, largely WHO class III (50%) at enrollment, with preserved average RV ejection fraction (RVEF) (47±11%). Mean follow-up was 3.2±1.3 years. Sixteen (62%) subjects met CW criteria. MB Ees/Ea was significantly lower in CW subjects (0.7±0.5 versus 1.3±0.8, P=0.02). The optimal MB Ees/Ea cut-point predictive of CW was 0.65, defined by ROC (AUC 0.78, P=0.01). MB Ees/Ea below this cut-point was significantly associated with time to CW (hazard ratio 5.1, P=0.001). MB Ees/Ea remained predictive of outcomes following multivariate adjustment for timing of PAH diagnosis and PAH diagnosis subtype. Conclusions RV-PA coupling as measured by MB Ees/Ea has prognostic significance in human PAH, even in a cohort with preserved RVEF.

Right heart failure in pulmonary hypertension: Diagnosis and new perspectives on vascular and direct right ventricular treatment

Adaptation of right ventricular (RV) function to increased afterload-known as RV-arterial coupling-is a key determinant of prognosis in pulmonary hypertension. However, measurement of RV-arterial coupling is a complex, invasive process involving analysis of the RV pressure-volume relationship during preload reduction over multiple cardiac cycles. Simplified methods have therefore been proposed, including echocardiographic and cardiac MRI approaches. This review describes the available methods for assessment of RV function and RV-arterial coupling and the effects of pharmacotherapy on these variables. Overall, pharmacotherapies for pulmonary hypertension have shown beneficial effects on various measures of RV function, but it is often unclear if these are direct RV effects or indirect results of afterload reduction. Studies of the effects of pharmacotherapies on RV-arterial coupling are limited and mostly restricted to experimental models. Simplified methods to assess RV-arterial coupling should be validated and incorporated into routine clinical follow-up and future clinical trials. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Impaired right ventricular lusitropy is associated with ventilatory inefficiency in pulmonary arterial hypertension

Cardiopulmonary exercise testing (CPET) is an important tool for assessing functional capacity and prognosis in pulmonary arterial hypertension (PAH). However, the associations of CPET parameters with the adaptation of right ventricular (RV) function to afterload remain incompletely understood.In this study, 37 patients with PAH (idiopathic in 31 cases) underwent single-beat pressure-volume loop measurements of RV end-systolic elastance (Ees), arterial elastance (Ea) and diastolic elastance (Eed). Pulmonary arterial stiffness was assessed by magnetic resonance imaging. The results were correlated to CPET variables. The predictive relevance of RV function parameters for clinically relevant ventilatory inefficiency, defined as minute ventilation/carbon dioxide production (V' _E/V' _CO2 ) slope >48, was evaluated using logistic regression analysis.The median (interquartile range) of the V' _E/V' _CO2 slope was 42 (32-52) and the V' _E/V' _CO2 nadir was 40 (31-44). The mean±sd of peak end-tidal carbon dioxide tension (P _ETCO2 ) was 23±8 mmHg. Ea, Eed and parameters reflecting pulmonary arterial stiffness (capacitance and distensibility) correlated with the V' _E/V' _CO2 slope, V' _E/V' _CO2 nadir, P _ETCO2 and peak oxygen pulse. RV Ees and RV-arterial coupling as assessed by the Ees/Ea ratio showed no correlations with CPET parameters. Ea (univariate OR 7.28, 95% CI 1.20-44.04) and Eed (univariate OR 2.21, 95% CI 0.93-5.26) were significantly associated with ventilatory inefficiency (p<0.10).Our data suggest that impaired RV lusitropy and increased afterload are associated with ventilatory inefficiency in PAH.

Right ventricular function in pulmonary (arterial) hypertension

The right ventricle (RV) is the main determinant of prognosis in pulmonary hypertension. Adaptation and maladaptation of the RV are of crucial importance. In the course of disease, RV contractility increases through changes in muscle properties and muscle hypertrophy. At a certain point, the point of "uncoupling," the afterload exceeds contractility, and maladaptation as well as dilation occurs to maintain stroke volume (SV). To understand the adaptational processes and to further develop targeted medication directly affecting load-independent contractility, an accurate and precise assessment of contractility and RV-pulmonary artery (PA) coupling should be performed. In this review, we shed light on existing methods to assess RV function, including the gold standard measurement of contractility and RV-PA coupling, and we evaluate existing surrogates of RV-PA coupling.

Validation of the Tricuspid Annular Plane Systolic Excursion/Systolic Pulmonary Artery Pressure Ratio for the Assessment of Right Ventricular-Arterial Coupling in Severe Pulmonary Hypertension

BACKGROUND

The ratios of tricuspid annular plane systolic excursion (TAPSE)/echocardiographically measured systolic pulmonary artery pressure (PASP), fractional area change/invasively measured mean pulmonary artery pressure, right ventricular (RV) area change/end-systolic area, TAPSE/pulmonary artery acceleration time, and stroke volume/end-systolic area have been proposed as surrogates of RV-arterial coupling. The relationship of these surrogates with the gold standard measure of RV-arterial coupling (invasive pressure-volume loop-derived end-systolic/arterial elastance [Ees/Ea] ratio) and RV diastolic stiffness (end-diastolic elastance) in pulmonary hypertension remains incompletely understood. We evaluated the relationship of these surrogates with invasive pressure-volume loop-derived Ees/Ea and end-diastolic elastance in pulmonary hypertension.

METHODS

We performed right heart echocardiography and cardiac magnetic resonance imaging 1 day before invasive measurement of pulmonary hemodynamics and single-beat RV pressure-volume loops in 52 patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. The relationships of the proposed surrogates with Ees/Ea and end-diastolic elastance were evaluated by Spearman correlation, multivariate logistic regression, and receiver operating characteristic analyses. Associations with prognosis were evaluated by Kaplan-Meier analysis.

RESULTS

TAPSE/PASP, fractional area change/mean pulmonary artery pressure, RV area change/end-systolic area, and stroke volume/end-systolic area but not TAPSE/pulmonary artery acceleration time were correlated with Ees/Ea and end-diastolic elastance. Of the surrogates, only TAPSE/PASP emerged as an independent predictor of Ees/Ea (multivariate odds ratio: 18.6; 95% CI, 0.8-96.1; P=0.08). In receiver operating characteristic analysis, a TAPSE/PASP cutoff of 0.31 mm/mm Hg (sensitivity: 87.5% and specificity: 75.9%) discriminated RV-arterial uncoupling (Ees/Ea <0.805). Patients with TAPSE/PASP <0.31 mm/mm Hg had a significantly worse prognosis than those with higher TAPSE/PASP.

CONCLUSIONS

Echocardiographically determined TAPSE/PASP is a straightforward noninvasive measure of RV-arterial coupling and is affected by RV diastolic stiffness in severe pulmonary hypertension.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT03403868.