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  • EMBOLISMDr.CSBR.Prasad, M.D.

  • Def: An embolus is a detached intravascular solid, liquid, or gaseous mass that is carried by the blood to a site distant from its point of origin.

  • Almost all emboli represent some part of a dislodged thrombus Unless specified embolism means Thromboembolism

  • Rare forms of embolidroplets of fatbubbles of air or nitrogenCholesterol emboli from AS debritumor fragmentsbits of bone marrow, or even foreign bodies such as bullets

  • Effect of embolusOcclusion

    Emboli lodge in vessels too small to permit further passage, resulting in partial or complete vascular occlusion

  • ConsequencesInfarction

    The potential consequence of such thromboembolic events is the ischemic necrosis of distal tissue, known as infarction

  • Clinical outcomeDepends on: the site of origin & the site of lodgment

    The clinical outcomes are best understood from the standpoint of whether emboli lodge in the pulmonary or systemic circulations.

    Depending on the site of origin, emboli may lodge anywhere in the vascular tree; the clinical outcomes are best understood from the standpoint of whether emboli lodge in the pulmonary or systemic circulations.

  • Saddle embolusLerisch syndromeParadoxical embolism

  • PULMONARY THROMBOEMBOLISMIncidence of 20 to 25 per 100,000 hospitalized patients

    In more than 95% of instances, venous emboli originate from deep leg vein thrombi

    Depending on the size of the embolus, it may occlude the main pulmonary artery, impact across the bifurcation (saddle embolus), or pass out into the smaller, branching arterioles

    in general, the patient who has had one pulmonary embolus is at high risk of having more.

    Rarely, an embolus may pass through an interatrial or interventricular defect to gain access to the systemic circulation (paradoxical embolism)

    PULMONARY THROMBOEMBOLISM:Incidence of 20 to 25 per 100,000 hospitalized patientsAlthough the rate of fatal pulmonary emboli (as assessed at autopsy) has declined from 6% to 2% over the last quarter centurypulmonary embolism still causes about 200,000 deaths per year in the United States. In more than 95% of instances, venous emboli originate from deep leg vein thrombi They are carried through progressively larger channels and usually pass through the right side of the heart into the pulmonary vasculature. Depending on the size of the embolus, it may occlude the main pulmonary artery, impact across the bifurcation (saddle embolus), or pass out into the smaller, branching arterioles ( Fig. 4-17 ). Frequently, there are multiple emboli, perhaps sequentially or as a shower of smaller emboli from a single large mass; in general, the patient who has had one pulmonary embolus is at high risk of having more. Rarely, an embolus may pass through an interatrial or interventricular defect to gain access to the systemic circulation (paradoxical embolism). A more complete discussion of pulmonary emboli is presented in Chapter 15 ; an overview is offered here.[43][44]

  • PULMONARY THROMBOEMBOLISMMost pulmonary emboli (60% to 80%) are clinically silent because they are small. With time, they undergo organization and are incorporated into the vascular wall in some cases, organization of the thromboembolus leaves behind a delicate, bridging fibrous web.

    Sudden death, right heart failure (cor pulmonale). or cardiovascular collapse occurs when 60% or more of the pulmonary circulation is obstructed with emboli.

    Embolic obstruction of medium-sized arteries may result in pulmonary hemorrhage but usually does not cause pulmonary infarction because of the dual blood flow into the area from the bronchial circulation. A similar embolus in the setting of left-sided cardiac failure (i.e., with sluggish bronchial artery flow), however, may result in a large infarct.

    Embolic obstruction of small end-arteriolar pulmonary branches usually does result in associated infarction. Multiple emboli over time may cause pulmonary hypertension with right heart failure.

  • Consequences of Pul.embolismThe morphologic consequences depend on the size of the embolic mass and the general state of the circulationLarge emboli - Sudden death often ensues - acute cor pulmonale (ECG-elecromechanical dissociation)Smaller emboli

    with good CVS hemorrhages resorption & reconstitution of the preexisting architecture with CVS compromise - 10% infarction

    The morphologic consequences of embolic occlusion of the pulmonary arteries depend on the size of the embolic mass and the general state of the circulation. Large emboli may impact in the main pulmonary artery or its major branches or lodge at the bifurcation as a saddle embolus ( Fig. 15-27 ). Sudden death often ensues, owing largely to the blockage of blood flow through the lungs. Death may also be caused by acute failure of the right side of the heart (acute cor pulmonale). Smaller emboli can travel out into the more peripheral vessels, where they may cause infarction. In patients with adequate cardiovascular function, the bronchial arterial supply can often sustain the lung parenchyma despite obstruction to the pulmonary arterial system. Under these circumstances, hemorrhages may occur, but there is no infarction of the underlying lung parenchyma. Only about 10% of emboli actually cause infarction. Although the underlying pulmonary architecture may be obscured by the suffusion of blood, hemorrhages are distinguished by the preservation of the pulmonary alveolar architecture; in such cases, resorption of the blood permits reconstitution of the preexisting architecture ====================A large pulmonary embolus is one of the few causes of virtually instantaneous death. During cardiopulmonary resuscitation in such instances, the patient frequently is said to have electromechanical dissociation, in which the electrocardiogram has a rhythm but no pulses are palpated because of the massive blockage of blood in the systemic venous circulation.

  • Here is large pulmonary thromboembolus seen in cross section of this lung. The typical source for such thromboemboli is from large veins in the legs and pelvis.

    Here is another large pulmonary thromboembolus seen in cross section of this lung. The typical source for such thromboemboli is from large veins in the legs and pelvis.

  • This pulmonary thromboembolus is occluding the main pulmonary artery. Persons who are immobilized for weeks are at greatest risk. The patient can experience sudden onset of shortness of breath. Death may occur within minutes.

  • Figure 4-17 Large embolus derived from a lower extremity deep venous thrombosis and now impacted in a pulmonary artery branch

    Figure 4-17 Large embolus derived from a lower extremity deep venous thrombosis and now impacted in a pulmonary artery branch

  • Pulmonary thromboembolus

    A pulmonary thromboembolus travels from a large vein in the leg up the inferior vena cava to the main pulmonary arteries as they branch. Such thrombi embolize most often from large veins in the legs and pelvis where thrombi form with stasis.

  • This is the microscopic appearance of a pulmonary embolus (PE) in a major pulmonary artery branch

  • Recent, small, roughly wedge-shaped hemorrhagic pulmonary infarct

    Figure 15-28 Recent, small, roughly wedge-shaped hemorrhagic pulmonary infarct.

  • Non thrombotic forms of pul.emboliuncommon but potentially lethalair (may be iatrogenic) bone marrow (after trauma and bone marrow necrosis in sickle cell patients) fat (trauma and surgery)amniotic fluid (during parturition) and foreign bodies (in I/V drug abusers)

  • SYSTEMIC THROMBOEMBOLISM refers to emboli travelling within the arterial circulation Common source: Mural thrombi in heart (80%)Less common source: Aorta (AS, Aneurysm)

  • Mural thrombi

    Figure 4-14 Mural thrombi. A, Thrombus in the left and right ventricular apices, overlying a white fibrous scar. B, Laminated thrombus in a dilated abdominal aortic aneurysm.

  • SYSTEMIC THROMBOEMBOLISM The major sites for arteriolar embolizationLower extremities (75%) and Brain (10%)the intestines, kidneys, spleen, and upper extremities involved to a lesser extent

    The major sites for arteriolar embolization are the lower extremities (75%) and the brain (10%), with the intestines, kidneys, spleen, and upper extremities involved to a lesser extent.

  • SYSTEMIC THROMBOEMBOLISM The consequences of systemic emboli depend on:the extent of collateral vascular supply in the affected tissue the tissue's vulnerability to ischemia and the caliber of the vessel occludedin general, arterial emboli cause infarction of tissues downstream of the obstructed vessel

    The major sites for arteriolar embolization are the lower extremities (75%) and the brain (10%), with the intestines, kidneys, spleen, and upper extremities involved to a lesser extent.

  • Tissues supplied by end-arteries without significant collateral supplies will be the most susceptible.Obstruction of blood supply leads to ischemia which when prolonged leads to necrosis and atrophy.Where there is reperfusion after ischemic necrosis the tissues will show a hemorrhagic necrosis.Where there is infection by Clostridia (gram positive bacilli), gangrene sets in.

  • FAT EMBOLISM Presence of microscopic fat globules in the circulation Causes: # of long bones

    Soft tissue trauma Burns

  • FAT EMBOLISM Fat embolism syndrome is characterized by pulmonary insufficiency, neurologic symptoms, anemia, and ThrombocytopeniaSymptoms:typically begin 1 to 3 days afte