Does Deep Vein Thrombosis Usually Precede a Pulmonary Embolism

Abstract

BackgroundHistorically, traumatic brain injury, pelvic and lower extremity fractures, paralysis or any condition associated with prolonged immobilization were considered risk factors for Deep Vein Thrombosis [DVT] [1] which can predispose to a potentially life threatening pulmonary embolism [PE], a process known as Venous Thromboembolism [VTE] [2]. There is no disputing that the incidence of VTE depends on a patient's risk factors along with the modalities used to prevent and detect DVT and PE. However, there is some dispute as to whether a PE is usually preceded by a DVT, detected or undetected, and whether the prophylactic use of inferior vena cava filters is appropriate in these patients. Some recent studies suggest PEs are not always from a DVT but instead may originate from thrombi formed within the pulmonary vasculature following severe chest trauma [3]. In past years common knowledge presumed that a PE invariably resulted from a DVT within the deep veins of the lower extremities or within the pelvic iliac veins. Since not all DVTs are detected on ultrasound studies, the iliac veins were usually considered as the originating site when a PE was diagnosed without a positive ultrasound study for DVT. However, recent studies showed that in some patients who had experienced PE had a negative ultrasound and Computed Topography [CT] of the pelvis failed to reveal DVTs within the iliac veins as previously suspected [3][4][5]. These studies support the fact that PE may potentially develop de novo in the pulmonary circulation and not deep within the iliac veins as originally suspected [5]. In addition, the American College of Surgeons found the incidence of PE to be 42% higher in patients who sustained serious chest injury, defined as an Abbreviated Injury Scale score of 3 or higher, compared to those without serious chest injury [3]. In summary, these referenced studies provide data suggesting that patients with chest trauma are more at risk for PEs that originate from the pulmonary vasculature than originally thought. This twelve-year retrospective study was performed for the purpose of comparing the correlation of DVT and subsequent PE in the trauma population with and without severe chest trauma. PathophysiologyThree factors predispose to thrombus formation: endothelial injury, stasis or turbulence in blood flow, and hypercoagulability. These three factors are known as Virchow's triad. Endothelial injury occurs any time the collagen within the vasculature is damaged and the clotting cascade is initiated. Examples of injury to the endothelium can be damage to the vein from trauma or hypertension. With vessel injury, an alteration in blood flow occurs, causing turbulence and stasis within the vessel. Blood hypercoagulability is a result of a complex mechanism known as the clotting cascade. The clotting cascade involves several components, including platelets and numerous clotting factors used to maintain blood homeostasis. The clotting factors are composed of enzymes and proteins. In addition, there are three mai...