Pulmonary blood density quantified by CMR is reduced in newly diagnosed systemic sclerosis, consistent with pulmonary arteriolar proliferation

Methods Twenty-seven SSc patients (9 men, 30-79 years, 18 limited cutaneous SSc, 3 diffuse cutaneous SSc, and 6 early SSc) and 20 healthy subjects (13 men, 18-46 years) underwent CMR. The PBV was calculated as the product of cardiac output determined by velocity encoded CMR, and the pulmonary transit time determined as the time for a 2 ml intravenously administered contrast bolus to pass from the pulmonary trunk to the left atrium, as previously validated. The lung volume was determined by planimetry using transversal MR images covering the lungs. The PBD was defined as the PBV divided by the lung volume. Also, the blood flow in the pulmonary artery and the pulmonary veins was measured using velocity encoded CMR. The PBVV was calculated by integration of the difference in arterial and venous pulmonary flow over the cardiac cycle. Results Compared to healthy subjects, SSc patients had lower PBV (460±85 vs 602±125ml, p<0.01), lower PBD (16±5 vs 21±2%, p<0.001; 15/27 (56%) had PBD below normal limits), but no difference in PBVV/stroke volume (40±8 vs 46±10%, p=0.12). PBD correlated with Doppler echocardiography estimated pulmonary artery pressure (r=-0.36, p<0.05) and the diffusion capacity for carbon monoxide (DLCO) in the lungs (r=0.44, p=0.02), but was not affected by pulmonary fibrosis by high-resolution computed tomography (p=0.34).