Abstract
BackgroundPulmonary involvement, manifested as pulmonary arterial hypertension or pulmonary fibrosis, is the most common cause of death in systemic sclerosis (SSc). We aimed to explore the feasibility of detecting early pulmonary involvement in SSc using recently developed non-invasive quantitative measures of pulmonary physiology using cardiovascular magnetic resonance (CMR).MethodsTwenty-seven SSc patients (9 men, 57 ± 13 years) and 10 healthy controls (3 men, 54 ± 9 years) underwent CMR to determine the pulmonary blood volume (PBV) and the PBV variation (PBVV) throughout the cardiac cycle. Patients underwent Doppler echocardiography, high-resolution computed tomography (HRCT), and pulmonary function testing by spirometry. Comparisons were performed using the unpaired t-test and linear regression analysis was performed with Pearson’s correlation coefficient (r).ResultsCompared to healthy controls, the PBV indexed to lung volume (PBVI) was lower in patients (16 ± 4 vs 20 ± 5%, p < 0.05). There was no difference in PBV (466 ± 87 vs 471 ± 122 mL, p = 0.91) or PBVV/stroke volume (45 ± 10 vs 40 ± 6%, p = 0.09). There were no significant correlations between PBVI and pulmonary artery pressure estimated by Doppler (p = 0.08) the lung’s diffusion capacity for carbon monoxide (DLCO) (p = 0.09), vital capacity (p = 0.45), or pulmonary fibrosis by HRCT (p = 0.74).ConclusionsThis study is the first to measure the PBV in humans using CMR. Compared to healthy controls, newly diagnosed SSc patients have a reduced amount of blood in the pulmonary vasculature (PBVI) but unchanged pulmonary vascular distensibility (PBVV/stroke volume). PBVI is unrelated to DLCO, pulmonary artery pressure, vital capacity, and the presence of pulmonary fibrosis. PBVI may be a novel parameter reflecting vascular lung involvement in early-stage SSc, and these findings may be consistent with pathophysiological changes of the pulmonary vasculature.
Highlights
Pulmonary involvement, manifested as pulmonary arterial hypertension or pulmonary fibrosis, is the most common cause of death in systemic sclerosis (SSc)
The major finding in this study is that patients with newly diagnosed SSc, as a group, have a reduced amount of blood in the pulmonary vasculature normalized to lung size (PBVI) but an unaffected pulmonary vascular distensibility (PBVV/stroke volume), compared to healthy controls
Compared to healthy controls, patients with newly diagnosed SSc have, as a group, a reduced amount of blood in the pulmonary vasculature (PBVI) but an unaffected pulmonary vascular distensibility (PBVV/stroke volume), not related to the presence of pulmonary fibrosis-related pathology on high-resolution computed tomography (HRCT), estimated pulmonary artery pressure, DLCO or reduced vital capacity (VC). This implies that the pulmonary blood volume indexed to lung volume (PBVI) may reflect the morphology of the SSc lung since the majority of the patients did not show any clinical sign of pulmonary involvement
Summary
Pulmonary involvement, manifested as pulmonary arterial hypertension or pulmonary fibrosis, is the most common cause of death in systemic sclerosis (SSc). PAH develops as a result of pulmonary vascular pathology whereas pulmonary hypertension may be secondary to severe interstitial lung disease [4]. Pulmonary fibrosis, which may occur in the absence of skin lesions, [7] may lead to an impaired gas exchange due to altered physiology in the alveolae. This impairment can be measured by studying the diffusion capacity for carbon monoxide in the lungs (DLCO) [8]
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