Prognostic utility of right atrial emptying fractions in pulmonary arterial hypertension

Imaging the right atrium in pulmonary hypertension: A systematic review and meta-analysis

BACKGROUND

Right atrial (RA) imaging has emerged as a promising tool for the evaluation of patients with pulmonary hypertension (PH), albeit without systematic validation.

METHODS

PubMed, Web of Science and the Cochrane library were searched for studies investigating the prognostic value of RA imaging assessment in patients with PH from 2000 to June 2021 (PROSPERO Identifier: CRD42020212850). An inverse variance-weighted meta-analysis of univariable hazard ratios (HRs) was performed using a random effects model.

RESULTS

Thirty-five studies were included (3,476 patients with PH; 74% female, 86% pulmonary arterial hypertension). Risk of bias was low/moderate (Quality of Prognosis Studies checklist). RA area (HR 1.06; 95% confidence interval [CI] 1.04-1.08), RA indexed area (HR 1.09; 95% CI 1.04-1.14), RA peak longitudinal strain (PLS; HR 0.94; 95% CI 0.91-0.97) and RA total emptying fraction (HR 0.96; 95% CI 0.94-0.98) were significantly associated with combined end-points including death, clinical worsening and/or lung transplantation; RA volume and volume index showed marginal significant associations. RA area (HR 1.06; 95% CI 1.04-1.07), RA indexed area (HR 1.12; 95% CI 1.07-1.17) and RA PLS (HR 0.98; 95% CI 0.97-0.99) showed significant associations with mortality; RA total emptying fraction showed a marginal association.

CONCLUSIONS

Imaging-based RA assessment qualifies as a relevant prognostic marker in PH. RA area reliably predicts composite end-points and mortality, which underscores its clinical utility. RA PLS emerged as a promising imaging measure, but is currently limited by the number of studies and different acquisition methods.

Impaired Relaxation and Reduced Lusitropic Reserve in Atrial Myocardium in the Obese Patients

Background: Obesity can influence the structure and function of the atrium, but most studies focused on the relationship of body mass index (BMI) and overt left atrium (LA) dysfunction as assessed by clinical imaging. We combined the assessment of right atrium (RA) function in vivo and in vitro in obese and non-obese patients scheduled for elective cardiac surgery.

Methods: Atrial structure and function were quantified pre-operatively by echocardiography. RA tissue removed for the establishment of extracorporeal support was collected and RA trabeculae function was quantified in vitro at baseline and with adrenergic stimulation (isoproterenol). Fatty acid-binding protein 3 (FABP3) was quantified in RA tissue. Results were stratified according to the BMI of the patients.

Results: About 76 patients were included pre-operatively for the echocardiographic analysis. RA trabeculae function at baseline was finally quantified from 46 patients and RA function in 28 patients was also assessed with isoproterenol. There was no significant correlation between BMI and the parameters of atrial function measured by the clinical echocardiography. However, in vitro measurements revealed a significant correlation between BMI and a prolonged relaxation of the atrial myocardium at baseline, which persisted after controlling for the atrial fibrillation and diabetes by the partial correlation analysis. Acceleration of relaxation with isoproterenol was significantly lower in the obese group (BMI ≥ 30 kg/m²). As a result, relaxation with adrenergic stimulation in the obese group remained significantly higher compared to the overweight group (25 kg/m² ≤ BMI < 30 kg/m², p = 0.027) and normal group (18.5 kg/m² ≤ BMI < 25 kg/m², p = 0.036). There were no differences on impacts of the isoproterenol on (systolic) developed force between groups. The expression of FABP3 in the obese group was significantly higher compared to the normal group (p = 0.049) and the correlation analysis showed the significant correlations between the level of FABP3 in the RA trabeculae function.

Conclusion: A higher BMI is associated with the early subclinical changes of RA myocardial function with the slowed relaxation and reduced adrenergic lusitropy.

Right atrial structure and function in patients with hypertension and with chronic heart failure

BACKGROUND

Prior studies have shown that both heart failure (HF) and atrial fibrillation (AF) are factors that impact left atrial function and structure. However, right atrial (RA) function measured as RA emptying fraction (RAEF) on echocardiography has not been analyzed systematically in a chronic HF population. The aim of this study was to assess RA volume index (RAVI) and RAEF in patients with chronic HF and patients with hypertension (HTN) and to relate these findings to other cardiopulmonary ultrasound parameters and 12-month outcomes.

METHODS AND RESULTS

In this prospective observational study, we identified 119 patients with chronic HF (64 patients without a history of AF [HF without AF], 55 with AF [HF with AF]), and 127 patients with HTN but without important cardiac disease who underwent routine outpatient transthoracic echocardiography. We found that RAEF was impaired in patients with HF without AF compared to patients with HTN (35% ±2 vs 50% ±1, P < .001), whereas RAVI did not differ between these two groups. Lower RAEF was associated with larger RAVI and higher estimated RA pressures but not with a higher degree of pulmonary congestion by lung ultrasound. Both lower RAEF and higher RAVI were associated with an increased risk of 12-month HF hospitalizations or all-cause death (age, sex, and AF adjusted HR: 4.07, 95% CI: 1.69-9.79; P = .002, vs 2.74, 95% CI: 1.15-6.54, P = .023).

CONCLUSIONS

In an outpatient HF cohort, both lower RAEF and increased RAVI were associated with other markers of impaired cardiac function and 12-month adverse events.

Right atrial strain is predictive of clinical outcomes and invasive hemodynamic data in group 1 pulmonary arterial hypertension

Transthoracic echocardiography (TTE) is a practical and widely used tool for risk stratification in pulmonary arterial hypertension (PAH). We hypothesized that right atrial (RA) reservoir function, represented by peak RA systolic strain, correlates with invasive hemodynamic measurements and clinical outcomes in PAH. Patients with group 1 PAH who had TTE within 6 months of index PAH clinic visit and right heart catheterization were included in this retrospective study. Peak RA strain in the 2D apical 4-chamber view was measured with speckle-tracking software. The primary endpoint was a composite of prostacyclin initiation, lung transplantation, and death. RA strain was also measured in healthy control subjects. Among the 37 patients studied, 25 (68%) met the primary endpoint. RA strain was significantly lower among patients who met the primary endpoint than among those who did not (mean 20% vs. 33%, P = 0.002). Strain was lower in PAH patients than in controls (mean 24% vs. 35%, P = 0.0001). RA strain correlated negatively with hemodynamic data including RA pressure (R = -0.31), mean pulmonary arterial pressure (R = -0.33), and pulmonary vascular resistance (R = -0.39), and positively with cardiac index (R = 0.44). In receiver operating characteristic analysis to distinguish between patients meeting the primary endpoint and event-free survivors, RA strain was not significantly different from RA volume, right ventricular (RV) fractional area change, RV basal diameter, or right ventricular systolic pressure (area under the curve 0.82, 0.81, 0.83, 0.86, and 0.97, respectively). Our results demonstrate that RA strain is predictive of clinical outcomes in PAH. Further research is needed to determine if RA strain is independently associated with outcomes in this population.

Echocardiographic assessment of the right ventricle: Impact of the distinctly load dependency of its size, geometry and performance

Right ventricular (RV) size, shape and function are distinctly load-dependent and pulmonary load is an important determinant of RV function in patients with congestive heart failure (CHF) due to primary impaired left ventricular function and in those with pre-capillary pulmonary hypertension (PH). In a pressure overloaded RV, not only dilation and aggravation of tricuspid regurgitation, but also systolic dysfunction leading to RV failure (RVF) can occur already before the development of irreversible alterations in RV myocardial contractility. This explains RV ability for reverse remodeling and functional improvement in patients with post-capillary and pre-capillary PH of a different etiology, after normalization of loading conditions. There is increasing evidence that RV evaluation by echocardiography in relation with its loading conditions can improve the decision-making process and prognosis assessments in clinical praxis. Recent approaches to evaluate the RV in relation with its actual loading conditions by echo-derived composite variables which either incorporate a certain functional parameter (i.e. tricuspid annulus peak systolic excursion, stroke volume, RV end-systolic volume index, velocity of myocardial shortening) and load, or incorporate measures which reflect the relationship between RV load and RV dilation, also taking the right atrial pressure into account (i.e. "load adaptation index"), appeared particularly suited and therefore also potentially useful for evaluation of RV contractile function. Special attention is focused on the usefulness of RV echo-evaluation in relation to load for proper decision making before ventricular assist-device implantation in patients with CHF and for optimal timing of listing procedures to transplantation in patients with end-stage pre-capillary PH.

Right atrial emptying fraction non-invasively predicts mortality in pulmonary hypertension

Right-sided heart failure is the most common cause of death in pulmonary hypertension (PH). Echocardiographic measurements of right atrial (RA) size are associated with worse outcome in PH, however the association between RA function and death in PH has not been well-described. 160 PH patients (World Health Organization groups 1-5) underwent cardiac magnetic resonance imaging (cMRI) and right heart catheterization (RHC) within 6 weeks of each other at a tertiary care academic medical center in the United States. We measured cMRI RA maximum and minimum volumes indexed to body surface area and calculated RA emptying fraction (RAEF). We evaluated the relationship between RAEF and clinical variables with death using Cox proportional hazard models. 57 deaths occurred during a median follow-up of 3.5 years (36 % died overall, 10 % per year). RAEF was directly correlated in univariate analyses with right ventricular (RV) ejection fraction, left ventricular (LV) ejection fraction, LV size, cardiac index, absence of tricuspid and pulmonic regurgitation, absence of pericardial effusion, estimated glomerular filtration rate, 6-minute walk distance, and pulmonary arterial oxygen saturation, whereas it was inversely correlated with death, BNP, heart rate, mean RA pressure, mean PA pressure, pulmonary and systemic vascular resistance, RV size, and RA size. Using multivariate analyses, RAEF had a robust inverse association with death after adjusting for measured risk factors (HR per 5 % change in RAEF: 0.83 [95 % CI 0.73-0.94], p = 0.003). In PH patients, decreased RAEF by cMRI is independently associated with worse survival after adjustment for other risk factors.