Echocardiographic insights redefining risk in pulmonary arterial hypertension: a focus on right atrial volume index for enhanced stratification
Authors: Brochado L , Luz J , Fazendas P , Ferreira F , Grade J , Martinho M , Ferreira B , Cunha D , Baltazar O , Ilchyshyn N , Pereira H 
Published: October 2024

Abstract

Introduction
In Pulmonary arterial hypertension (PAH), the right atrium plays a critical role, and its size, determined by echocardiography, is crucial for risk stratification. Despite this, current guidelines still prioritize right atrial area (RAA) over the right atrial volume index (RAVI). This approach is contrary to the recommendations of international echocardiography societies since 2016, which advocate for the use of RAVI for a more accurate assessment.

Purpose
Identify the RAVI value corresponding to the RAA, in PAH risk stratification used in the 2022 ESC guidelines.

Methods
We conducted a retrospective analysis of all consecutive patients of a single-center, since 2002. Patient's echocardiograms were revised for simultaneous assessment of RAA and right atrial volume index (RAVI). Over an average follow-up of 6.7 years (SD 5.9), we recorded a cohort of 82 patients diagnosed with PAH. From this group, we excluded 27 patients with congenital etiologies, 14 due to the insufficient quality of echocardiographic data, and one patient identified as an extreme statistical outlier. A Pearson's correlation analysis was used to access the correlation between RAA and RAVI for PAH diagnosis.

Results
A total of 40 patients were included with a mean age at diagnosis of 48.85 years (SD 17.82), predominantly female (77.5 %). The most prevalent etiologies were idiopathic (32.5%) and connective tissue disease-associated PAH (27.5%). Clinical presentations included right heart failure signs in 30% of patients, rapid symptom progression in 12.5%, syncope history in 15% and 77.5% in WHO-FC III-IV. Average 6-MWD and NT-proBNP levels were 392,1 m (SD 120,2) and 1636,18 ng/L (SD 2576,14), respectively. Average hemodynamics parameters were right atrial pressure 7,39 mmHg (SD 4,940); cardiac index 2,28 L/min/m2 (SD 2,06); stroke volume index 3,38 mL/m2 (SD 3,92) and mixed venous oxygen saturation 65,68% (SD 10,86). Average echocardiographic parameters were RAA 20,14 cm2 (SD 4,80); TAPSE/sPAP 0,34 mm/mmHg (SD 0,18) and RAVI 37,78 mL/m2 (SD 13,67), with 10% of pericardial effusion. Statistical analysis revealed a strong and significant correlation between RAA and RAVI (r=0.82, 95% CI: 0.69-0.90, p&lt;0.001). The derived linear relationship is expressed as "y=2.8*X -18". Therefore, an RAA value of 18 cm² translates to a RAVI of 32 mL/m², while an RAA of 26 cm² corresponds to a RAVI of 55 mL/m².

Conclusion
Our study supports a revision in HAP risk assessment guidelines, suggesting a shift to a more comprehensive approach using right atrial volume index (RAVI) measurements. We propose categorizing risk as low for RAVI &lt; 32 mL/m², intermediate for RAVI between 32 and 55 mL/m², and high for RAVI &gt; 55 mL/m². This recommendation aligns with the standards of international societies and is grounded in best clinical practices, considering that indexing measurements of the right atrium to body size potentially offers greater accuracy than absolute values.