An embolism is any intravascular mass that has been carried down the bloodstream from its site of origin, resulting in the occlusion of a vessel. There are many types of emboli:
· Thromboemboli: most common (98%)
· Atheromatous emboli (severe atherosclerosis)
· Fat emboli (bone fractures and soft tissue trauma)
· Bone marrow emboli (bone fractures and cardiopulmonary resuscitation [CPR])
· Gas emboli cause decompression sickness (“the bends” and caisson disease) when rapid ascent results in nitrogen gas bubbles in the blood vessels
· Amniotic fluid emboli are a complication of labor that may result in DIC; fetal squamous cells are seen in the maternal pulmonary vessels
· Tumor emboli (metastasis)
· Talc emboli (IV drug abuse)
· Bacterial/septic emboli (infectious endocarditis)
Pulmonary emboli (PE) are often clinically silent and are the most commonlymissed diagnosis in hospitalized patients. They are found in almost 50% of all hos-pital autopsies. Most PE (95%) arise from deep leg vein thrombosis (DVT) in the leg; other sources include the right side of the heart and the pelvic venous plexuses of the prostate and uterus.
Diagnosis of a PE can be established when V/Q lung shows a scan V/Q mismatch. Doppler ultrasound of the leg veins can be used to detect a DVT. Additionally, plasma D-dimer ELISA test is elevated.
Most cases are clinically silent and resolve.
Infarction is more common in patients with cardiopulmonary compromise. Symp-toms include shortness of breath, hemoptysis, pleuritic chest pain, and pleural effu-sion. On gross examination there is typically a hemorrhagic wedge-shaped infarct. The infarction heals by regeneration or scar formation.
· Sudden death can occur when large emboli lodge in the bifurcation (saddle embolus) or large pulmonary artery branches.
· Chronic secondary pulmonary hypertension is caused by recurrent PEs, which increase pulmonary resistance and lead to secondary pulmonary hypertension.