Structure, mechanical properties, and modeling of cyclically compressed pulmonary emboli

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Materials Science

Background:

• Pulmonary embolism (PE) is a life-threatening condition caused by lung blood clots (emboli).
• The mechanical behavior of emboli under physiological compressive forces is poorly understood.
• Understanding embolus mechanics is crucial for predicting their response to in vivo forces.

Purpose of the Study:

• To investigate the mechanical properties of human pulmonary emboli under cyclic compression.
• To characterize the stress-strain responses and structural changes of emboli.
• To develop a model explaining embolus behavior based on composition and red blood cell (RBC) rupture.

Main Methods:

• Human pulmonary emboli were subjected to cyclic compression tests.
• Stress-strain responses were measured and analyzed.
• Electron and confocal microscopy were used to examine structural changes.
• A mechanical model incorporating RBC rupture and fluid flow was developed.

Main Results:

• Emboli exhibited a hysteretic stress-strain curve, characteristic of foams.
• Fibrin fibers and RBCs within emboli were damaged irreversibly by compression.
• Embolus composition (fibrin vs. RBCs) significantly influenced mechanical response.
• RBCs ruptured at a critical stress, and a model predicted phase transitions within the compressed embolus.

Conclusions:

• Pulmonary emboli possess distinct mechanical properties influenced by their composition.
• Compression causes structural damage and irreversible changes in emboli.
• The findings provide a basis for classifying emboli and predicting their behavior under physiological stress.