Pulmonary blood volume redistribution in COVID-19 patients of different severity and its predictive value for six-month outcomes in the less pathogenic Omicron variant.

BACKGROUND

The redistribution of pulmonary blood volume (PBV) across COVID-19 severity levels and its prognostic value for the less pathogenic, predominantly upper respiratory tract-infecting Omicron variant remain unclear. This study investigates PBV distribution patterns and validates its predictive utility for Omicron outcomes.

METHODS

This retrospective study enrolled consecutive patients (November 2022-January 2023) with baseline CT and clinical data, followed for six months. Patients were divided into mild/moderate (MM) and severe/critical (SC) groups according to COVID-19 severity. Pre-trained deep learning algorithms quantified total, lobar, and vessel-size-specific PBV. Adjusted multivariable analyses determined odds ratios (OR) for clinical outcomes, and logistic regression models based on PBV were constructed to predict adverse events.

RESULTS

Among 921 patients (61 ± 20 years, 460 men), 755 were in the MM group and 166 in the SC group. Compared to MM patients, SC patients showed significantly lower total PBV (259 mL vs. 239 mL, p = 0.002) and redistribution from lower to upper lobes (upper vs. lower; MM, 21% vs. 23%; SC, 23% vs. 18%) and from small-calibre (≤5 mm2, 44% vs. 32%, p < 0.0005) to large-calibre (>10 mm2, 39% vs. 51%, p < 0.0005) vessels. PBV (especially in vessels ≤5 mm2) predicted six-month composite outcomes (OR = 4.66, AUC = 0.79, sensitivity = 92%) and mortality (OR = 3.34, AUC = 0.75, sensitivity = 93%) for the Omicron variant with high sensitivity, but at a higher risk threshold (42%) than that reported for more pathogenic variants in previous publications.

CONCLUSIONS

Severe/critical COVID-19 is associated with reduced PBV and its redistribution across lung regions and vessel sizes. PBV retains predictive value for clinical outcomes in the immune-evasive Omicron variant.