Role of 3D echocardiography‐determined atrial volumes in distinguishing between pre‐capillary and post‐capillary pulmonary hypertension

AIMS: The current guidelines on pulmonary hypertension (PH) recommend the use of invasive examination for differentiating between left‐sided heart disease‐related (post‐capillary) and pre‐capillary PH. However, atrial sizes are considered markers of ventricular filling pressures. Therefore, we aimed to test the clinical applicability of atrial volumes measured by transthoracic three‐dimensional echocardiography (3DE) in differentiating between pre‐capillary and post‐capillary PH. METHODS AND RESULTS: Seventy‐five consecutive patients with PH were prospectively examined with transthoracic 3DE. After less than 24 h, the patients underwent right heart catheterization and 3DE and were classified as pre‐capillary or post‐capillary PH according to the recommendations of the ESC guidelines. The atrial volumes were measured offline with dedicated commercial software. Thirty‐eight patients (13 men, age 65 ± 18 year) had pre‐capillary PH, and 37 (23 men, age 62 ± year) had post‐capillary PH. The mean pulmonary artery pressures were similar in patients with pre‐capillary and post‐capillary PH (38 [IQR 26, 54] mmHg vs. 41 [IQR 33, 48] mmHg, respectively, P = 0.49). The left atrial indexed maximum (LAVi max) and minimum (LAVi min) volumes were significantly larger in the post‐capillary PH patient group than in the pre‐capillary PH patient group (LAVi max: 64 ± 32 mL/m(2) vs. 41 ± 25 mL/m(2), P = 0.001; LAVi min: 50 ± 22 mL/m(2) vs. 26 ± 24 mL/m(2), P < 0.0001). The indexed right atrial minimum volume (RAVi min) was also higher in patients with post‐capillary PH (51 ± 27 mL/m(2) vs. 38 ± 26 mL/m(2); P = 0.02). Both the left atrial (LA) and right atrial (RA) volumes, especially the LA minimum volume, correlated with the pulmonary artery wedge pressure (PAWP) (r = 0.62 (P < 0.0001) for LAV min vs. r = 0.49 (P < 0.0001) for LAV max; r = 0.32 (P = 0.005) for RAV min vs. r = 0.24 (P = 0.04) for RAV max). Multivariate logistic regression analysis showed that LAVi min was an independent predictor of post‐capillary PH. In the receiver operating characteristic (ROC) curves of parameters predicting the post‐capillary PH, the areas under the curve (AUC) for LAVi min, LAVi max, and RAVi min were 0.86 (95% CI, 0.76–0.95), 0.78 (95% CI, 0.67–0.89), and 0.66 (0.53–0.78), respectively. Concerning the performance of the atrial volume ratio for differentiating post‐capillary PH, the AUC of the atrial volume ratio was significantly lower [AUC: 0.66 (95% CI, 0.53–0.78)]. The ROC analysis indicated a possible cutoff value of 27.7 mL/m(2) for LAVi min to predict post‐capillary PH (AUC = 0.86; sensitivity = 86%, specificity = 76%). CONCLUSIONS: The BSA‐indexed left atrial minimum volume measured by transthoracic 3DE is a useful parameter for differentiating pre‐capillary from post‐capillary pulmonary hypertension.