Hemodynamic Disorders PDF

Fatima obeidat,MD University of Jordan, School of medicine  Processes that maintain blood in a fluid, clot-free state in normal vessels while rapidly forming a localized hemostatic plug at the site of vascular injury.  The pathologic counterpart of hemostasis is thrombosis, the format...

Fatima obeidat,MD University of Jordan, School of medicine  Processes that maintain blood in a fluid, clot-free state in normal vessels while rapidly forming a localized hemostatic plug at the site of vascular injury.  The pathologic counterpart of hemostasis is thrombosis, the formation of blood clot (thrombus) within intact vessels.  Three elements:  1.The vascular wall.  2. Platelets.  3.The coagulation cascade  Primary abnormalities that lead to thrombus formation (called Virchow’s triad):  (1) endothelial injury,  (2) stasis or turbulent blood flow, and  (3) hypercoagulability of the blood  Examples:  1. In cardiac chambers after myocardial infarction.  2. Over ulcerated atherosclerotic plaques  3. At sites of traumatic or inflammatory vascular injury (vasculitis).  Turbulence leads to arterial and cardiac thrombosis by endothelial injury.  Stasis is a major factor in the development of venous thrombi.  Important underlying risk factor for venous thrombosis.  Primary (inherited) hypercoagulability:  young patients (>>Larger leg veins at or above the knee joint.  >>>popliteal, femoral, and iliac veins  >>> more serious, prone to embolization.  >>>cause local pain and edema.  >>>Asymptomatic in 50% of patients, recognized after they embolize to lungs.  Superficial or the deep veins of the leg.  Superficial venous thrombi  >>>> in saphenous system,  >>>>varicose veins.  >>>>rarely embolize  >>>>painful, congestion and swelling.  >>>> Impaired venous outflow  >>>>varicose ulcers  95% of cases originate from thrombi within deep leg veins above knee level.  Depending on size, a PE can occlude the main pulmonary artery, lodge at the bifurcation of the right and left pulmonary arteries (saddle embolus), or pass into the smaller, branching arterioles.  Recurrence.  Most pulmonary emboli (60% to 80%) are small and clinically silent.  Large embolus that blocks a major pulmonary artery can cause sudden death. (saddle embolus)  Embolic obstruction of medium-sized arteries and subsequent rupture of capillaries can cause pulmonary hemorrhage.  Embolism to small end-arteriolar pulmonary branches usually causes infarction.  Multiple emboli occurring over time can cause pulmonary hypertension and right ventricular failure (cor pulmonale).  Origin of systemic emboli  1.Most systemic emboli (80%) arise from intracardiac mural thrombi;  >>>left ventricular infarcts.  >>>dilated left atrium  2.Aortic aneurysms  3.Thrombi overlying ulcerated atherosclerotic plaques,  4.10% to 15% unknown origin.