Pulmonary Vascular Remodeling in Smokers: A Systematic Review of Quantitative CT and Histologic Evidence.

Pulmonary vascular remodeling is increasingly recognized as an important yet underappreciated component of smoking-related lung disease and may contribute to the early development of pulmonary hypertension (PH) in susceptible individuals. This systematic review examined human studies evaluating the association between cigarette smoking and quantitative measures of pulmonary vascular remodeling assessed through histologic analysis or computed tomography (CT). A comprehensive search of PubMed, Embase, and Scopus covering publications from 1990 to 2024 identified eight eligible studies, including cross-sectional and cohort designs. Histologic investigations demonstrated thickening of the intimal and medial layers, reduction in small arterial numbers, and altered elastin deposition in smokers and individuals with mild to moderate chronic obstructive pulmonary disease (COPD). CT-based studies consistently showed distal vascular pruning, reflected by reduced blood vessel volume in vessels less than 5 mm² (BV5) to total blood vessel volume (TBV) ratios and decreased percentage of cross-sectional area in vessels under 5 mm² (%CSA<5). These findings correlated with airflow limitation, functional impairment, or hemodynamic markers relevant to PH. Across study designs, a coherent pattern emerged indicating that vascular remodeling can appear early in smoking-exposed populations and may be disproportionate to parenchymal disease. These insights suggest that quantitative CT metrics may serve as noninvasive indicators of early pulmonary vascular pathology and support the recognition of a vascular-predominant phenotype in some smokers. Further longitudinal studies integrating smoking exposure, imaging, and hemodynamic assessment are needed to clarify causality and improve risk stratification for PH in this population.