Nailfold Microvascular Abnormalities Are Associated with the Standardized In-Hospital Blood-Pressure Phenotype and Carotid Wall Thickness in Treated Hypertension: An Integrated Vascular Phenotyping Study

Background/Objectives: Hypertension damages the microcirculation, endothelium, and large arteries, yet these domains are rarely assessed together. We examined whether nailfold microvascular abnormalities track the standardized in-hospital blood-pressure phenotype and carotid wall thickness. Methods: Cross-sectional secondary analysis of 217 treated hypertensive adults hospitalized July 2025–June 2026. Phenotyping included nailfold capillaroscopy, flow-mediated dilation, reactive hyperemia index, pulse wave velocity, and carotid ultrasonography. A prespecified exploratory 0–10 microvascular score summarized rarefaction, impaired flow, and morphological abnormalities. Outcomes were the uncontrolled standardized in-hospital BP phenotype (SBP ≥ 140 and/or DBP ≥ 90 mmHg) and mean carotid intima–media thickness (cIMT). Results: Of 217 patients (mean age 61.3 ± 9.9 years; 50.7% men), 145 (66.8%) met the uncontrolled standardized in-hospital BP phenotype. The score was higher in that group (median 3 [IQR 2–4] vs. 2 [1,2,3], p < 0.001) and correlated with cIMT (Spearman ρ = 0.536; FDR-adjusted p < 0.001). Each point was associated with higher adjusted odds of the uncontrolled standardized in-hospital BP phenotype (OR 1.70, 95% CI 1.31–2.20; p < 0.001) and 0.0076 mm higher cIMT (95% CI 0.0004–0.0147; p = 0.040), attenuated in the expanded sensitivity model (p = 0.138). Conclusions: Greater nailfold microvascular abnormality burden was associated with the uncontrolled standardized in-hospital BP phenotype and an adverse multidomain vascular phenotype. The cIMT association was modest and adjustment-sensitive. These cross-sectional findings concern a protocolized in-hospital BP measurement session and do not establish 24 h, home, or long-term BP control or distinguish sustained uncontrolled hypertension from white-coat or masked uncontrolled BP patterns. Prospective external validation is required.