Acoustic Trapping of Cholesterol Particles in Coronary Arteries: Angiographic and Machine Learning Analysis

When a tank connected to a draining pipe has its distal valve abruptly closed, the adjacent fluid column stops while the upstream fluid continues moving, creating a localized pressure surge. This retrograde propagation, known as the water hammer effect, imposes high mechanical stress on the pipe and its components. Similarly, in the cardiovascular system, the aorta acts as a reservoir and the coronary artery as the draining channel. During diastole, coronary flow is antegrade; at systole, left ventricular contraction functions as a distal valve, halting flow and generating a retrograde pressure wave that collides with the forward column.

Acoustic trapping arises when such retrograde waves create pressure gradients that confine microscopic particles—such as low-density lipoproteins cholesterol particles—within the flow. These gradients generate acoustic radiation forces that oppose hydrodynamic drag, driving particles toward pressure nodes or antinodes. With the new dynamic coronary recording technique, contrast motion reflects these oscillations: dense regions mark compression, while lighter ones indicate rarefaction. Frame-to-frame angiographic and machine learning analysis detects the movement and interference patterns, revealing consistent energy-trapping zones or “acoustic nodes” that correspond to oscillatory shear and prolonged particle residence. They are the key players to endothelial injury, atherosclerotic plaque initiation and development.