Reduced DLCO flags early right-heart strain in systemic sclerosis despite short disease duration
T Prata Branco, E Andrade, L Alves, B Couto Viana, B Cruz, J Conde Goncalves, E Oliveira, H Moreira, P Mangas Palma, M Rocha, A Pinho, N Alves, R Lopes, C Sousa, R RodriguesAbstract
Background
Systemic sclerosis (SSc) is a multisystem autoimmune disease frequently complicated by pulmonary vascular involvement and right ventricular (RV) dysfunction, which are major determinants of heart failure and prognosis. Cardiopulmonary manifestations may develop early in the disease course, often preceding overt pulmonary hypertension. However, in patients with short disease duration, the extent to which pulmonary function impairment reflects early right-heart involvement remains incompletely understood.
Purpose
To investigate the association between echocardiographic parameters of RV function and pulmonary function indices in a contemporary cohort of patients with systemic sclerosis and relatively short disease duration.
Methods
We conducted a cross-sectional study including 36 patients with SSC who underwent comprehensive transthoracic echocardiography and pulmonary function testing. Echocardiographic assessment focused on right-sided structure and function, including tricuspid annular plane systolic excursion (TAPSE), tricuspid annular systolic velocity (S′), right atrial size and estimated pulmonary artery systolic pressure (PASP). Pulmonary function evaluation included diffusing capacity for carbon monoxide (DLCO) and forced vital capacity (FVC). Associations between echocardiographic and respiratory parameters were assessed using Spearman correlation analysis.
Results
Mean age was 59.4±7.8 years, 94.4% were female and all patients had limited cutaneous SSc. Median disease duration was 2.5 years (IQR 1.0–4.0). Median DLCO was 81.6% predicted (IQR 66.0–93.7), while median FVC was preserved at 99.9% predicted (IQR 89.7–114.9). RV systolic function was largely preserved, with a median TAPSE of 21.5 mm (IQR 20.0–24.0). Median PASP was 25.0 mmHg (IQR 21.5–28.0; n=30), and median NT-proBNP was 93.6 pg/mL (IQR 35.6–143.0; n=34). Lower DLCO was significantly associated with higher PASP (ρ=−0.49; p=0.006) and higher NT-proBNP levels (ρ=−0.51; p=0.002). FVC showed weaker associations, correlating with NT-proBNP (ρ=−0.45; p=0.007) and only a non-significant trend with PASP. Patients with DLCO <60% predicted exhibited significantly higher PASP (29.0 vs 24.0 mmHg; p=0.001) and NT-proBNP concentrations (155.4 vs 67.5 pg/mL; p=0.001).
Conclusion
In SSC patients with short disease duration and preserved spirometric lung volumes, impaired pulmonary gas transfer emerges as a sensitive marker of early right-heart haemodynamic stress. Reduced DLCO was closely associated with higher PSAP and biomarker evidence of myocardial strain, despite preserved conventional indices of RV systolic function. These findings indicate that cardiopulmonary coupling is established early in the disease course and support DLCO as a pragmatic red flag to prompt intensified RV-focused echocardiographic surveillance and early pulmonary vascular assessment, potentially preventing progression to overt pulmonary hypertension and right-sided heart failure.