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

Abstract

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/m² vs. 41 ± 25 mL/m² , P = 0.001; LAVi min: 50 ± 22 mL/m² vs. 26 ± 24 mL/m² , P < 0.0001). The indexed right atrial minimum volume (RAVi min) was also higher in patients with post-capillary PH (51 ± 27 mL/m² vs. 38 ± 26 mL/m² ; 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/m² 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.

Keywords: 3-dimensional; Echocardiography; Left atrial volume; Post-capillary pulmonary hypertension; Pre-capillary pulmonary hypertension; Right atrial volume.