Left atrial dysfunction as a determinant of pulmonary hypertension in patients with severe aortic stenosis and preserved left ventricular ejection fraction

Peak atrial longitudinal strain and risk stratification in moderate and severe aortic stenosis

AIMS

We sought to investigate the association of left atrial strain with the outcome in a large cohort of patients with at least moderate aortic stenosis (AS).

METHODS AND RESULTS

We analysed 467 patients (mean age 80.6 ± 8.2 years; 51% men) with at least moderate AS and sinus rhythm. The primary study endpoint was the composite of all-cause mortality and hospitalizations for heart failure. After a median follow-up of 19.2 (inter-quartile range 12.5-24.4) months, 96 events occurred. Using the receiver operator characteristic curve analysis, the cut-off value of peak atrial longitudinal strain (PALS) more strongly associated with outcome was <16% {area under the curve (AUC) 0.70 [95% confidence interval (CI): 0.63-0.78], P < 0.001}. The Kaplan-Meier curves demonstrated a higher rate of events for patients with PALS < 16% (log-rank P < 0.001). On multivariable analysis, PALS [adjusted HR (aHR) 0.95 (95% CI 0.91-0.99), P = 0.017] and age were the only variables independently associated with the combined endpoint. PALS provided incremental prognostic value over left ventricular (LV) global longitudinal strain, LV ejection fraction, and right ventricular function. Subgroup analysis revealed that impaired PALS was also independently associated with outcome in the subgroups of paucisymptomatic patients [aHR 0.98 (95% CI 0.97-0.98), P = 0.048], moderate AS [aHR 0.92, (95% CI 0.86-0.98), P = 0.016], and low-flow AS [aHR 0.90 (95% CI 0.83-0.98), P = 0.020].

CONCLUSION

In our patients with at least moderate AS, PALS was independently associated with outcome. In asymptomatic patients, PALS could be a potential marker of sub-clinical damage, leading to better risk stratification and, potentially, earlier treatment.

Main pulmonary artery diameter in combination with cardiovascular biomarkers: new possibilities to identify pulmonary hypertension in patients with severe aortic valve stenosis

BACKGROUND

Echocardiography is currently the noninvasive method of choice to screen patients with severe aortic valve stenosis (AS) for pulmonary hypertension (PH) by estimating systolic pulmonary artery pressure (sPAP). However, radiological options are also available by determining the main pulmonary artery (MPA) diameter in the setting of CT angiography. The aim of the present study was to compare cardiovascular biomarkers with the MPA diameter to allow other ways of detecting PH in patients with severe AS.

METHODS

One hundred ninety-four patients with severe AS undergoing transcatheter aortic valve replacement (TAVR) were included in this study and were divided into two groups based on the CT-angiographically determined MPA diameter. In accordance with ESC guidelines, a cut-off value of 29 mm was determined in this study, with the absence of PH defined by an MPA diameter <29 mm (N79/194) and the presence of PH defined by an MPA diameter ≥29 mm (115/194). Immediately before interventional aortic valve replacement, blood samples were drawn from the subjects and relevant cardiovascular biomarkers such as BNP, cTnI, GDF-15, H-FABP, IGF-BP2 and suPAR were assessed.

RESULTS

Patients with an MPA diameter ≥29 mm had significantly higher BNP (P=0.004), cTnI (P=0.039) and H-FABP (P=0.015) plasma levels, whereas GDF-15 (P=0.140), IGF-BP2 (P=0.088) and suPAR (P=0.140) showed no significant differences. In addition, cut-off values were calculated to predict an MPA diameter ≥29 mm. Significant results were shown with 1634.00 pg/mL for BNP (P=0.004), with 16.50 pg/mL for cTnI (P=0.039) and with 1.16 ng/mL for H-FABP (P=0.016). In a combined biomarker analysis, the 2-way combination of BNP and IGF-BP2 (AUC 0.671; 95%CI 0.538-0.805; P=0.023) and the 3-way combination of BNP, H-FABP and IGF-BP2 (AUC 0.685; 95%CI 0.551-0.818; P=0.015) showed the best results. Biomarker follow-up at 3 and 12 months after TAVR did not require additional information gain. Regarding 1-year survival, no significant difference could be detected between patients with an MPA diameter<29 mm compared to patients with ≥29 mm (log-rank test: P=0.262).

CONCLUSIONS

The MPA diameter remains a controversial parameter for the detection of PH in patients with severe AS. Standing on its own, this non-invasive parameter may not be precise enough to detect PH accurately. Combining this parameter with several biomarkers did not provide significant additional information.

A Story of PA/BSA and Biomarkers to Diagnose Pulmonary Hypertension in Patients with Severe Aortic Valve Stenosis-The Rise of IGF-BP2 and GDF-15

(1) Background: Currently, echocardiography is the primary non-invasive diagnostic method used to screen patients with severe aortic valve stenosis (AS) for pulmonary hypertension (PH) by estimating systolic pulmonary artery pressure (sPAP). Other radiological methods have been a focus of research in the past couple of years, as it was shown that by determining the pulmonary artery (PA) diameter, prognostic statements concerning overall mortality could be made in these patients. This study compared established and novel cardiovascular biomarkers with the PA/BSA value to detect PH in patients with severe AS. (2) Methods: The study cohort comprised 188 patients with severe AS undergoing transcatheter aortic valve replacement (TAVR), who were then divided into two groups based on PA/BSA values obtained through CT-angiography. The presence of PH was defined as a PA/BSA ≥ 16.6 mm/m2 (n = 81), and absence as a PA/BSA < 16.6 mm/m2 (n = 107). Blood samples were taken before TAVR to assess cardiovascular biomarkers used in this study, namely brain natriuretic peptide (BNP), cardiac troponin I (cTnI), high-sensitive troponin (hsTN), soluble suppression of tumorigenesis-2 (sST2), growth/differentiation factor 15 (GDF-15), heart-type fatty acid-binding protein (H-FABP), insulin-like growth factor binding protein 2 (IGF-BP2), and soluble urokinase-type plasminogen activator receptor (suPAR). (3) Results: Patients with a PA/BSA ≥ 16.6 mm/m2 showed significantly higher levels of BNP (p = <0.001), GDF-15 (p = 0.040), and H-FABP (p = 0.007). The other investigated cardiovascular biomarkers did not significantly differ between the two groups. To predict a PA/BSA ≥ 16.6 mm/m2, cut-off values for the biomarkers were calculated. Here, GDF-15 (p = 0.029; cut-off 1172.0 pg/mL) and BNP (p < 0.001; cut-off 2194.0 pg/mL) showed significant results. Consequently, analyses of combined biomarkers were performed, which yielded IGF-BP2 + BNP (AUC = 0.721; 95%CI = 0.585−0.857; p = 0.004) as the best result of the two-way analyses and GDF-15 + IGF-BP2 + BNP (AUC = 0.727; 95%CI = 0.590−0.864; p = 0.004) as the best result of the three-way analyses. No significant difference regarding the 1-year survival between patients with PA/BSA < 16.6 mm/m2 and patients with PA/BSA ≥ 16.6 mm/m2 was found (log-rank test: p = 0.452). (4) Conclusions: Although PA/BSA aims to reduce the bias of the PA value caused by different body compositions and sizes, it is still a controversial parameter for diagnosing PH. Combining the parameter with different cardiovascular biomarkers did not lead to a significant increase in the diagnostic precision for detecting PH in patients with severe AS.

Right ventricle to pulmonary artery coupling after transcatheter aortic valve implantation-Determinant factors and prognostic impact

Introduction

Right ventricular (RV) dysfunction and pulmonary hypertension (PH) have been previously associated with unfavorable outcomes in patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve implantation (TAVI), but little is known about the effect of right ventricle (RV) to pulmonary artery (PA) coupling. Our study aimed to evaluate the determinant factors and the prognostic value of RV-PA coupling in patients undergoing TAVI.

Methods

One hundred sixty consecutive patients with severe AS were prospectively enrolled, between September 2018 and May 2020. They underwent a comprehensive echocardiogram before and 30 days after TAVI, including speckle tracking echocardiography (STE) for myocardial deformation analysis of the left ventricle (LV), left atrium (LA), and RV function. Complete data on myocardial deformation was available in 132 patients (76.6 ± 7.5 years, 52.5% men) who formed the final study population. The ratio of RV free wall longitudinal strain (RV-FWLS) to PA systolic pressure (PASP) was used as an estimate of RV-PA coupling. Patients were analyzed according to baseline RV-FWLS/PASP cut-off point, determined through time-dependent ROC curve analysis, as follows: normal RV-PA coupling group (RV-FWLS/PASP ≥0.63, n = 65) and impaired RV-PA coupling group (RV-FWLS/PASP < 0.63, n = 67).

Results

A significant improvement of RV-PA coupling was observed early after TAVI (0.75 ± 0.3 vs. 0.64 ± 0.3 before TAVI, p < 0.001), mainly due to PASP decrease (p < 0.001). LA global longitudinal strain (LA-GLS) is an independent predictor of RV-PA coupling impairment before and after TAVI (OR = 0.837, p < 0.001, OR = 0.848, p < 0.001, respectively), while RV diameter is an independent predictor of persistent RV-PA coupling impairment after TAVI (OR = 1.174, p = 0.002). Impaired RV-PA coupling was associated with a worse survival rate (66.3% vs. 94.9%, p-value < 0.001) and emerged as an independent predictor of mortality (HR = 5.97, CI = 1.44-24.8, p = 0.014) and of the composite endpoint of death and rehospitalization (HR = 4.14, CI = 1.37-12.5, p = 0.012).

Conclusion

Our results confirm that relief of aortic valve obstruction has beneficial effects on the baseline RV-PA coupling, and they occur early after TAVI. Despite significant improvement in LV, LA, and RV function after TAVI, RV-PA coupling remains impaired in some patients, it is mainly related to persistent pulmonary hypertension and is associated with adverse outcomes.

Left Atrial Remodeling in Response to Aortic Valve Replacement: Pathophysiology and Myocardial Strain Analysis

Severe aortic stenosis (AS) is the most common valve disease in the elderly and is associated with poor prognosis if treated only medically. AS causes chronic pressure overload, concentric left ventricular (LV) hypertrophy, myocardial stiffness, and diastolic dysfunction. This adverse remodeling also affects the left atrium (LA), which dilates and develops myocardial fibrosis, with a reduction in intrinsic function and a consequent high risk of the development of atrial fibrillation. Speckle-tracking echocardiography is able to detect myocardial dysfunction before other conventional parameters, such as LV ejection fraction, and also predict clinical outcomes. This review aims at describing LV and LA remodeling in AS and before and after aortic valve replacement and the usefulness of myocardial strain analysis in this clinical setting.

Molecular Approaches and Echocardiographic Deformation Imaging in Detecting Myocardial Fibrosis

The pathological remodeling of myocardial tissue is the main cause of heart diseases. Several processes are involved in the onset of heart failure, and the comprehension of the mechanisms underlying the pathological phenotype deserves special attention to find novel procedures to identify the site of injury and develop novel strategies, as well as molecular druggable pathways, to counteract the high degree of morbidity associated with it. Myocardial fibrosis (MF) is recognized as a critical trigger for disruption of heart functionality due to the excessive accumulation of extracellular matrix proteins, in response to an injury. Its diagnosis remains focalized on invasive techniques, such as endomyocardial biopsy (EMB), or may be noninvasively detected by cardiac magnetic resonance imaging (CMRI). The detection of MF by non-canonical markers remains a challenge in clinical practice. During the last two decades, two-dimensional (2D) speckle tracking echocardiography (STE) has emerged as a new non-invasive imaging modality, able to detect myocardial tissue abnormalities without specifying the causes of the underlying histopathological changes. In this review, we highlighted the clinical utility of 2D-STE deformation imaging for tissue characterization, and its main technical limitations and criticisms. Moreover, we focalized on the importance of coupling 2D-STE examination with the molecular approaches in the clinical decision-making processes, in particular when the 2D-STE does not reflect myocardial dysfunction directly. We also attempted to examine the roles of epigenetic markers of MF and hypothesized microRNA-based mechanisms aiming to understand how they match with the clinical utility of echocardiographic deformation imaging for tissue characterization and MF assessment.

Severe Aortic Valve Stenosis and Pulmonary Hypertension: A Systematic Review of Non-Invasive Ways of Risk Stratification, Especially in Patients Undergoing Transcatheter Aortic Valve Replacement

Patients with severe aortic valve stenosis and concomitant pulmonary hypertension show a significantly reduced survival prognosis. Right heart catheterization as a preoperative diagnostic tool to determine pulmonary hypertension has been largely abandoned in recent years in favor of echocardiographic criteria. Clinically, determination of echocardiographically estimated systolic pulmonary artery pressure falls far short of invasive right heart catheterization data in terms of accuracy. The aim of the present systematic review was to highlight noninvasive possibilities for the detection of pulmonary hypertension in patients with severe aortic valve stenosis, with a special focus on cardiovascular biomarkers. A total of 525 publications regarding echocardiography, cardiovascular imaging and biomarkers related to severe aortic valve stenosis and pulmonary hypertension were analyzed in a systematic database analysis using PubMed Central®. Finally, 39 publications were included in the following review. It was shown that the current scientific data situation, especially regarding cardiovascular biomarkers as non-invasive diagnostic tools for the determination of pulmonary hypertension in severe aortic valve stenosis patients, is poor. Thus, there is a great scientific potential to combine different biomarkers (biomarker scores) in a non-invasive way to determine the presence or absence of PH.

Cardiac Imaging for the Assessment of Left Atrial Mechanics Across Heart Failure Stages

The left atrium (LA) is emerging as a key element in the pathophysiology of several cardiac diseases due to having an active role in contrasting heart failure (HF) progression. Its morphological and functional remodeling occurs progressively according to pressure or volume overload generated by the underlying disease, and its ability of adaptation contributes to avoid pulmonary circulation congestion and to postpone HF symptoms. Moreover, early signs of LA dysfunction can anticipate and predict the clinical course of HF diseases before the symptom onset which, particularly, also applies to patients with increased risk of HF with still normal cardiac structure (stage A HF). The study of LA mechanics (chamber morphology and function) is moving from a research interest to a clinical application thanks to a great clinical, prognostic, and pathophysiological significance. This process is promoted by the technological progress of cardiac imaging which increases the availability of easy-to-use tools for clinicians and HF specialists. Two-dimensional (2D) speckle tracking echocardiography and feature tracking cardiac magnetic resonance are becoming essential for daily practice. In this context, a deep understanding of LA mechanics, its prognostic significance, and the available approaches are essential to improve clinical practice. The present review will focus on LA mechanics, discussing atrial physiology and pathophysiology of main cardiac diseases across the HF stages with specific attention to the prognostic significance. Imaging techniques for LA mechanics assessment will be discussed with an overlook on the dynamic (under stress) evaluation of the chamber.

The Central Role of Left Atrium in Heart Failure

In past cardiovascular medicine, the attention to the left ventricle-identified as the only indicator and determinant of healthy or unhealthy cardiac conditions- has systematically hidden the role of the left atrium (LA). The recent advances in cardiovascular imaging have provided a better understanding of LA anatomy, physiology, and pathology, making us realize that this functional structure is far from being an innocent spectator. We now know that the LA's mechanical and neuro-hormonal properties play a relevant part in several cardiovascular diseases, including atrial fibrillation, ischemic heart disease, valvular heart disease, and heart failure. The present review aims to describe the role of LA in the specific setting of heart failure. We provide currently available information on LA structure and function and summarize its role as a determinant of symptoms, prognosis, and potential therapeutic target in heart failure patients.

Incremental prognostic role of left atrial reservoir strain in asymptomatic patients with moderate aortic stenosis

Left atrial (LA) mechanics assessed by two-dimensional speckle tracking echocardiography (2D-STE) have not been extensively studied and clearly characterized in patients with moderate aortic stenosis (AS). Accordingly, we aimed to evaluate the usefulness of LA reservoir strain for risk stratification of asymptomatic patients with moderate AS. This retrospective study included all consecutive asymptomatic patients with moderate AS who underwent transthoracic echocardiography implemented with 2D-STE analysis of LA myocardial strain and strain rate indices at our Institution, between February 2011 and September 2019. During the follow-up period, we evaluated the occurrence of any of the following: (1) CV hospitalization; (2) The recourse to AS surgery; (3) Cardiac death or sudden death. A total of 186 patients (mean age 71.9 ± 12.7 years, 61.8% men) were included in the present study. During a mean follow-up of 2.3 ± 1.9 years, no patients died and 63 adverse CV events were recorded: 48 patients were hospitalized because of heart failure (28 patients), acute coronary syndrome (10 patients), arrhythmias (10 patients) and 15 patients underwent AS surgery. At the multivariate Cox regression analysis, type 2 diabetes mellitus (OR 1.87, 95%CI 1.05-3.34, p = 0.03), NT-proBNP (OR average 1.14, 95%CI 1.02-1.27, p = 0.02), average E/e' ratio (OR 1.07, 95%CI 1.01-1.15, p = 0.04) and most of all left atrial positive global strain (LA-GSA+) (OR 0.85, 95%CI 0.81-0.90, p < 0.0001) were independently associated with the outcome. LA-GSA+ (optimal cut-off ≤ 19%, AUC = 0.94, 87% sensitivity, 99% specificity, positive predictive value 99%, negative predictive value 88%) showed the highest diagnostic performance. An impaired LA reservoir strain can contribute to identify a subset of asymptomatic patients with moderate AS at higher risk, who may benefit from closer echocardiographic follow-up and/or early surgery.

Left atrial functional assessment and mortality in patients with severe aortic stenosis with sinus rhythm

BACKGROUND

Aortic valve stenosis (AS) is the most common primary valvular heart disease leading to surgical or percutaneous aortic valve replacement (AVR) in Europe and its prevalence keeps growing. While other risk factors in severe AS are well documented, little is known about the prognostic value of left atrial (LA) function in AS. Our aim is to clarify the relationship between LA function measured at severe AS diagnosis (evaluated by means of volumetric assessment) and all-cause mortality during follow-up.

METHODS

We retrospectively evaluated patients diagnosed with severe AS for the first time at our echocardiography laboratory. We evaluated LA reservoir, conduit and pump function by measuring LA volumes at different timings of cardiac cycle. Treatment strategy was decided according to heart team consensus and patient decision. We divided patients into groups according to terciles of LA reservoir, conduit and pump function. Primary outcome was defined by the occurrence of all-cause mortality during follow-up.

RESULTS

A total of 408 patients were included in the analysis, with a median follow-up time of 45 months (interquartile range 54 months). 57.9% of patients underwent AVR and 44.9% of patients registered the primary outcome during follow-up. Left atrial emptying fraction (LAEF) was the best LA functional parameter and the best overall parameter in discriminating primary outcome (AUC 0.845, 95%CI 0.81-0.88, P < 0.001). After adjustment for clinical, demographic and echocardiographic variables, cumulative survival of patients with LAEF < 37% and LAEF 37 to 53% relative to patients with LAEF ≥54% remained significantly lower (HR 13.91, 95%CI 6.20-31.19, P < 0.001 and HR 3.40, 95%CI 1.57-7.37, P = 0.002, respectively). After adjustment for AVR, excess risk of LAEF < 37% and LAEF 37 to 53% relative to LAEF ≥54% remained significant (HR 11.71, 95%CI 5.20-26.40, P < 0.001 and HR 3.59, 95%CI 1.65-7.78, P = 0.001, respectively).

CONCLUSIONS

In patients with a first diagnosis of severe AS, LA function, evaluated by means of volumetric assessment, is an independent predictor of all-cause mortality and a more potent predictor of death compared to classical severity parameters. These data can be useful to identify high-risk patients who might benefit of AVR.

Going beyond classic echo in aortic stenosis: left atrial mechanics, a new marker of severity

BACKGROUND

There is limited information regarding left atrial (LA) mechanics in aortic valve stenosis (AS). We assessed LA mechanics in AS through speckle-tracking echocardiography (STE) according to severity and prognosis.

METHODS

We included 102 patients diagnosed with severe AS (sAS) and 80 patients with moderate AS (mAS), all with preserved ejection fraction and no coronary artery disease. LA mechanics and left ventricular global longitudinal strain (LV-GLS) were assessed by STE. The cohort was followed-up for a median of 30 (IQR 12.6-50) months, and outcomes were determined (combined outcome of HF, death, and aortic valve replacement).

RESULTS

In our sample set, values of LV-GLS (- 18.5% vs - 17.1, p = 0.025), E/e' ratio (15.8 vs 18.4, p = 0.03), and global LA mechanics (LA ɛsys, 23% vs 13.8%, p < 0.001) were worse for sAS compared to those for mAS. However, LA ɛsys (AUC 0.85, 95% CI 0.78-0.90, p < 0.001), ɛe (AUC 0.83, 95% CI 0.75-0.88, p < 0.001), and ɛa (AUC 0.80, 95% CI 0.70-0.84, p < 0.001) were the best discriminators of sAS, with sensitivities higher than 85%. LA ɛsys showed a stronger correlation with both aortic valve area (r² = 0.6, p < 0.001) and mean LV/aortic gradient (r² = 0.55, p < 0.001) than LV-GLS (r² = 0.3 and r² = 0.25, p = 0.01). Either LV-GLS or LA ɛsys, but not the E/e' ratio, TAPSE, or RV/RA gradient, were a significant predictors of the combined outcome.

CONCLUSIONS

LA global strain was the best discriminator of severity, surpassing E/e' ratio and LV-GLS, and a significant predictor of prognosis in AS.

Assessment of the Right and Left Atrial Functions at Midterm After Surgical and Device Atrial Septal Defect Closure: A 2-Dimensional Speckle-Tracking Echocardiographic Study

OBJECTIVES

The available literature lacks data on the comparison of the functions of the right atrium (RA) and left atrium (LA) between surgical atrial septal defect (ASD) closure and percutaneous device ASD closure at follow-up durations of longer than 1 year. We sought to evaluate the RA and LA functions in patients who underwent surgical or device ASD closure between 1 and 5 years postprocedurally.

METHODS

The study population included 30 patients who underwent device ASD closure and 30 who underwent surgical ASD closure, who were matched for the procedural time, age, and sex, in addition to 30 control participants. The RA and LA functions were evaluated with 2-dimensional speckle-tracking echocardiography.

RESULTS

The LA systolic and early diastolic strain and strain rate values and the RA early diastolic strain rate in the device closure group were more likely to be abnormal than in the control group. The RA systolic and late diastolic strain and strain rate values, the RA early diastolic strain rate, and the LA early diastolic strain in the surgical closure group were more likely to be abnormal than in the control group. The RA systolic strain and strain rate in the surgical closure group were more likely to be abnormal than in the device closure group.

CONCLUSIONS

The LA reservoir and conduit functions and the RA contraction function in the patients who underwent device ASD closure and all of the RA functions and the LA conduit function in the patients who underwent surgical ASD closure were more likely to be abnormal than those in the control participants. The RA reservoir function in the surgical closure group was more likely to be abnormal than that in the device closure group.

The role of the left atrial function in the surgical management of aortic and mitral valve disease

The right management of both mitral and aortic disease can be challenging, especially in asymptomatic patients. The current guidelines recommend valve repair or replacement when symptoms arise or when there is an evident left ventricular dysfunction. However, deciding the optimal surgical timing can be very difficult, since the line between the absence of symptoms and being minimally symptomatic, especially in the elderly, is blurred. Another relevant issue regards the second surgical criterion: operating on a patient with a reduced left ventricular ejection fraction or with a dilated left ventricle might jeopardize the possibility of a fully reverse remodeling of the heart after surgery. In this scenario, the left atrium might play an important role. In particular, left atrial deformation might be a very useful tool to detect early ultrastructural alterations, and help or support guiding a patient-tailored treatment at an early stage, optimizing the outcome in the long term.

Pulmonary Hypertension in Aortic and Mitral Valve Disease

In patients with aortic and/or mitral valve disease the presence of pulmonary hypertension (PH) indicates a decompensated state of the disease with left ventricular and left atrial dysfunction and exhausted compensatory mechanism, i.e., a state of heart failure. Pulmonary hypertension in this context is the consequence of the backwards transmission of elevated left atrial pressure. In this form of PH, pulmonary vascular resistance is initially normal (isolated post-capillary PH). Depending on the extent and chronicity of left atrial pressure elevation additional pulmonary vascular remodeling may occur (combined pre- and post-capillary PH). Mechanical interventions for the correction of valve disease often but not always reduce pulmonary pressures. However, the reduction in pulmonary pressures is often modest, and persistent PH in these patients is common and a marker of poor prognosis. In the present review we discuss the pathophysiology and clinical impact of PH in patients with aortic and mitral valve disease, the comprehensive non-invasive and invasive diagnostic approach required to define treatment of PH, and recent insights from mechanistic studies, registries and randomized studies, and we provide an outlook regarding gaps in evidence, future clinical challenges, and research opportunities in this setting.