Microemboli

Microemboli are small embolic particles or bubbles that travel through the bloodstream and occlude small vessels. They are typically defined as emboli with a diameter of less than about 1 mm. Microemboli can be solid, including thrombotic fragments, cholesterol crystals, fat droplets, or tumor cells; or gaseous, such as air bubbles; or mixed. They may originate from the heart, arterial plaques, fat from fractures, air introduced during procedures, or from fat or septic emboli.

Clinically, microemboli can occlude arterioles in the brain, retina, lungs, or other tissues, producing microinfarcts that may be asymptomatic or cause transient or persistent deficits. In the brain they can contribute to cognitive impairment or stroke, particularly with chronic microembolization. In the lungs, venous microemboli can cause ventilation-perfusion defects, especially during surgery or in pulmonary hypertension.

Diagnosis is achieved with techniques such as transcranial Doppler ultrasound, which can detect microembolic signals during procedures or in certain diseases. Magnetic resonance imaging can reveal small diffusion-restricted lesions compatible with microinfarcts. Computed tomography can miss these tiny events. The workup aims to identify the source of emboli and to differentiate etiologies such as thrombotic, cholesterolic, fat, air, or septic origins.

Prevention and management focus on reducing embolic sources and procedural air or fat entry, including appropriate antithrombotic therapy when indicated, optimization of vascular risk factors, and meticulous surgical technique with air control and filtration when applicable. Treatment of acute microembolic events depends on the underlying cause; there is no universal antidote, and prognosis varies with the burden and location of lesions.