Hemodynamic stress as a mechanistic driver of systemic platelet activation in patent foramen ovale

Background

Patent Foramen Ovale (PFO) is associated with systemic platelet activation and thrombotic events. While paradoxical embolism is the prevailing explanation, emerging evidence suggests that abnormal intracardiac flow patterns may directly contribute to a prothrombotic phenotype. Computational fluid dynamics studies indicate that blood cells traversing PFO tunnels are exposed to elevated shear stress, raising the hypothesis that mechanical forces per se may trigger platelet activation.

Purpose

To determine whether PFO-like hemodynamic conditions are sufficient to induce platelet activation and erythrocyte damage using a microfluidic platform reproducing PFO-associated mechanical stress.

Methods

Two microfluidic chips were engineered: one reproducing PFO-like geometries and shear conditions (Figure), and a linear channel as physiological flow control. Whole blood from 10 healthy donors was perfused through the devices. Platelet activation was assessed by flow cytometry measuring P-selectin, activated GPIIbIIIa (aGPIIbIIIa), reactive oxygen species (ROS), and Tissue Factor (TF). Erythrocyte integrity was evaluated by cell count and free heme release.

Results

Passage through the PFO-mimicking chip significantly increased the proportion of P-selectin–positive platelets compared with baseline (31.17 ± 9.16% vs 6.95 ± 4.47%; p=0.0006), whereas no increase was observed under linear flow conditions. The percentage of TF-positive platelets was also greater after PFO-chip perfusion (6.62 ± 1.33% vs 2.3 ± 0.78% at baseline; p = 0.0006) and was 2.8-fold higher than after linear flow. In contrast, aGPIIbIIIa expression and ROS production were not significantly modified by either condition. No significant erythrocyte lysis was detected, as cell counts and free heme levels remained unchanged.

Conclusions

Reproduction of PFO-like hemodynamic conditions in a microfluidic system is sufficient to induce a platelet phenotype characterized by P-selectin exposure and increased TF expression, closely resembling the prothrombotic profile observed in patients with PFO.

These findings identify intracardiac flow–mediated mechanical stress as a direct and independent trigger of systemic platelet activation, supporting a mechanistic link between structural heart abnormalities and thrombotic vulnerability beyond paradoxical embolism.

Figure. Microfluidic chip reproducing PFO-like geometries. a) AutoCAD software imagine used for project design (single and multiple feature); b) chip in use where blood flow can be observed.Microfluidic chip.