Correlation of Thoracic HRCT Scores with Right Heart Mechanics and TAPSE/sPAP Ratio in Pulmonary Alveolar Proteinosis

Background: Pulmonary Alveolar Proteinosis (PAP) is a rare interstitial lung disease characterized by intra-alveolar accumulation of lipoproteinaceous material. Although its radiologic features are well documented, the disease’s impact on cardiovascular mechanics—specifically right ventricular (RV) adaptation—remains underexplored. This study aims to explore the correlation between radiologic severity of parenchymal involvement, quantified by high-resolution computed tomography (HRCT) scores, and right heart hemodynamics, with a focus on RV-pulmonary artery (RV-PA) coupling and interventricular interaction. Methods: This retrospective observational study analyzed 13 adult patients with confirmed PAP and 70 age- and sex-matched healthy controls. All participants underwent concurrent thoracic HRCT and transthoracic echocardiography. Structural lung damage and “crazy-paving” patterns were quantified using a total lobar HRCT score ranging from 0 to 30. Echocardiographic evaluation assessed right heart hemodynamics, using the tricuspid annular plane systolic excursion-to-systolic pulmonary artery pressure ratio (TAPSE/sPAP) as an index of RV-PA coupling and the RV/LV ratio. Given the small sample size, p-values for correlations were adjusted for multiple comparisons using the Bonferroni method, and findings should be regarded as exploratory. Results: Left ventricular parameters were preserved across both groups. However, PAP patients had significantly impaired right heart indices compared with controls, including a larger RV basal diameter (37.2 ± 2.3 vs. 32.6 ± 1.6 mm, p < 0.001), higher sPAP (38.5 ± 3.5 vs. 23.6 ± 2.9 mmHg, p < 0.001), and a higher RV/LV ratio (0.98 ± 0.19 vs. 0.60 ± 0.06, p < 0.001). Furthermore, the RV-PA coupling marker, TAPSE/sPAP, was markedly reduced in the PAP cohort (0.43 ± 0.07 vs. 0.88 ± 0.13 mm/mmHg, p < 0.001). After Bonferroni correction, elevated HRCT scores remained strongly associated with a higher RV/LV ratio (r = 0.89, p < 0.001) and a lower TAPSE/sPAP ratio (r = −0.90, p < 0.001). Subgroup analysis indicated that patients with severe radiological scores had more pronounced RV enlargement and lower RV-PA coupling reserves. Conclusions: In this exploratory analysis, radiographic severity of alveolar lipoproteinaceous accumulation in PAP was strongly associated with isolated right ventricular dysfunction and impaired RV-PA coupling, despite preserved left heart function. These hypothesis-generating findings suggest that echocardiographic assessment of TAPSE/sPAP and RV/LV ratios may be useful for the clinical follow-up of PAP patients; however, causality cannot be inferred from this small, retrospective, single-center cohort, and larger prospective studies are warranted.