PE from Sites other than Proximal Thigh ======================================= ========================================================================== As many people have requested, here's a referenced section excerpted from the upcoming 4th edition of Rosen discussing embolization from sites other than proximal thigh: ========================================================================== ========================= Frequency of embolization ____________________ >From ileofemoral DVT Thrombus in the ileofemoral deep veins nearly always embolizes: current techniques allow us to demonstrate pulmonary embolism in 60 to 80 percent of patients with DVT in the popliteal or femoral veins, even though about half of these patients have no clinical symptoms to suggest pulmonary embolism.(1-3) Thrombus in the popliteal segment of the femoral vein is no different from thrombus in the upper thigh, as it also embolizes in more than 60% of cases.(4) There is no association between the degree of proximity of venous thrombus and the risk of subsequent embolization.(2) __________________ >From calf vein DVT The propensity of calf DVT to embolize is often inappropriately dismissed in the face of clear evidence to the contrary: Barnes, for example, discounted the importance of isolated calf-vein DVT even as he reported that "...calf deep vein thrombosis accounted for the only two instances of pulmonary embolism in this study."(5) The frequency of pulmonary thromboembolism from DVT isolated to the calf veins is 33 percent(4) to 46 percent.(6) A Scandinavian autopsy study specifically designed to determine the source of pulmonary emboli revealed the surprising fact that more than 35% of patients with pulmonary emboli had isolated calf vein thrombosis.(7) Emboli from calf veins often are of smaller calibre than those from more proximal venous segments, and this may present special risks: in a 1993 study of patients with identifiable thrombus causing paradoxical embolization through a patent foramen ovale, the source was isolated to the calf veins in 15 of 24 cases.(8) Not all emboli from calf veins are small, however. Perfusion scan defects are large or massive in 40 percent of the cases of embolism from calf veins.(4) It has been suggested that emboli from calf veins may be of less importance because many are "clinically silent". This is incorrect. The importance of a small thromboembolism as a sentinal event cannot be overemphasized: death usually comes not from the first embolus, but from those that follow.(9) At autopsy it is evident that most deaths from pulmonary embolus are preceded by multiple `clinically silent' smaller embolic events. Thrombus can propagate quickly from smaller veins into larger ones, so an initially "silent" embolus is not reassuring. There is no such thing as a `clinically insignificant' pulmonary embolism. Although calf vein thrombosis propagates above the knee in 87% of cases,(10) it can cause hemodynamic collapse and death without ever extending above the knee. In Hull's landmark 1983 study of angiography, V/Q scan, and venography in patients with suspected PE, the only death from proven PE was in a patient with isolated calf-vein thrombosis.(11) Most importantly, in Havig's prospective autopsy study, 25% of lethal pulmonary emboli, and 33% of "serious" pulmonary emboli arose from isolated calf vein thrombi.(7) In fact, clinically important embolization from calf vein DVT is the rule and not the exception. Despite published opinion to the contrary,(12) it must be recognized that deep venous thrombosis of the calf has been shown to be a significant source of pulmonary emboli, some of which may cause serious morbidity or death. One-third of serious pulmonary emboli have their source in the veins of the calf. The outdated characterization of calf vein DVT as a minor threat is inaccurate, and should be resisted lest it lull physicians into a false sense of security. _______________________ >From DVT at other sites Pulmonary thromboembolism may also arise from upper extremity veins, particularly in association with indwelling central venous catheters. Monreal(13) used V/Q scans to evaluate the prevalence of pulmonary embolism in 30 consecutive patients with deep venous thrombosis of the upper extremity. Significant lung perfusion defects were found in 1 of 10 patients with spontaneous upper-extremity DVT and in 6 of 20 patients with catheter-related DVT. The scans were essentially diagnostic of PE in four of these cases, and one additional patient could not undergo V/Q, but died 4 days later from massive PE proven at autopsy, thus PE is not a rare complication in upper extremity DVT. Embolism been reported from thrombosed neck veins, from renal veins, and from the vena cava. At autopsy, Muller(14) identified 10 fatalities in a single year from massive pulmonary thromboembolism that arose from catheter-associated thrombus in the innominate veins, the subclavian veins, or the superior vena cava. Autopsy records were reviewed in 5039 cases from 1975 through 1980 and from 1987 through 1988. Pulmonary embolism was detected in 1500 (30%) of the cases; the venous source was located in the legs in 59% of the cases and in the upper extremities or neck in 13%. No venous source of thrombus was found in 28% of cases. Most importantly, 628 (42.5%) of the cases of pulmonary embolism were judged to have been fatal, and the source of embolism was found within the upper venous tree (vena cava, jugular, subclavian, and innominate veins) in 8% of these fatal pulmonary emboli. Fully 10% (52/512) of the cases of isolated thrombus in the upper venous system were responsible for fatal embolism.(15) Finally, pulmonary thromboembolism can arise as a complication of myocardial contusion(16) or after myocardial infarction, as thrombus develops in the right heart due to a hypokinetic area of myocardium. ================================= Diagnosis of Deep Vein Thrombosis To be reliable, the diagnosis of deep vein thrombosis must be established through testing, because the clinical diagnosis of deep venous system thrombosis is only accurate 50 percent of the time, with as many false positives as negatives, even in the presence of pain, tenderness, and unilateral leg swelling.(17,18) Clinical findings are such insensitive and nonspecific indicators for deep vein thrombosis that more than two-thirds of patients with proven pulmonary thromboembolism lack any clinical evidence of venous thrombosis.(19) For this reason it is reasonable to test a patient with symptoms of pulmonary embolism for deep vein thrombosis even when clinical evidence of DVT is lacking. Several invasive and noninvasive tests are useful in the detection of deep vein thrombosis of the lower extremities (see box below). Unfortunately, venous studies of the lower extremities are negative in half of all patients with proven PE,(20) Often the source cannot be identified even at autopsy: in 1500 autopsy cases of pulmonary embolism, the venous source was located in the legs in 59% of the cases, in the upper extremities and neck in 13%, and the source could not be identified in 28% of cases.(15) For patient with symptoms of DVT, negative venous studies are fairly reliable, but for patients with suspected PE, venous studies are helpful only when positive, and are of virtually no prognostic value when negative. ============ Bibliography 1. Moser KM, Fedullo PF, LitteJohn JK, Crawford R. Frequent asymptomatic pulmonary embolism in patients with deep venous thrombosis. JAMA 1994; 271:223-225. 2. Monreal M, Ruiz J, Olazabal A, Arias A, Roca J. Deep venous thrombosis and the risk of pulmonary embolism. A systematic study [see comments]. Chest 1992; 102:677-681. 3. Huisman MV, Buller HR, Ten Cate JW, van Royen EA, Vreeken J, Kersten MJ, et al. Unexpected high prevalence of silent pulmonary embolism in patients with deep venous thrombosis. Chest 1989; 95:498-502. 4. Moreno-Cabral R, Kistner RL, Nordyke RA. Importance of calf vein thrombophlebitis. Surgery 1976; 80:735-742. 5. Barnes RW, Nix ML, Barnes CL, Lavender RC, Golden WE, Harmon BH, et al. Perioperative asymptomatic venous thrombosis: Role of duplex scanning versus venography. J Vasc Surg 1989; 9:251-260. 6. Kohn H, Konig B, Mostbeck A. Incidence and clinical feature of pulmonary embolism in patients with deep vein thrombosis: a prospective study. Eur J Nucl Med 1987; 13 Suppl:S11-5:S11-5. 7. Havig O. Deep vein thrombosis and pulmonary embolism. An autopsy study with multiple regression analysis of possible risk factors. Acta Chir Scand 1977; 478:1-120. 8. Stollberger C, Slany J, Schuster I, Leitner H, Winkler WB, Karnik R. The prevalence of deep venous thrombosis in patients with suspected paradoxical embolism [published erratum appears in Ann Intern Med 1994 Feb 15;120(4):347]. Ann Intern Med 1993; 119:461-465. 9. Morpurgo M. Pulmonary embolism: the dimensions of the problem. G Ital Cardiol 1984; Suppl., N:3-5. 10. Cogo A, Lensing AW, Prandoni P, Hirsh J. Distribution of thrombosis in patients with symptomatic deep vein thrombosis. Implications for simplifying the diagnostic process with compression ultrasound. Arch Intern Med 1993; 153:2777-2780. 11. Hull RD, Hirsh J, Carter CJ. Diagnostic value of ventilation perfusion lung scanning in patients with suspected pulmonary embolism. Chest 1985; 88:819 12. Dunmire SM. Thromboembolic Diseases. Foresight 1995; 1-8. 13. Monreal M, Lafoz E, Ruiz J, Valls R, Alastrue A. Upper-extremity deep venous thrombosis and pulmonary embolism. A prospective study. Chest 1991; 99:280-283. 14. Muller KM, Blaeser B. [Fatal thrombo-embolism after central-vein catheterisation (author's transl)]. Dtsch Med Wochenschr 1976; 101:411-413. 15. Diebold J, Lohrs U. Venous thrombosis and pulmonary embolism. A study of 5039 autopsies. Pathol Res Pract 1991; 187:260-266. 16. Timberlake GA, McSwain NE, Jr. Thromboembolism as a complication of myocardial contusion: a new capricious syndrome. J Trauma 1988; 28:535-540. 17. Haeger K. The treatment of varicosis in the post-thrombotic state. Zentralbl Phlebol 1969; 8(1):56-59. 18. Richards KL, Armstrong JD, Jr., Tikoff G, Hershgold EJ, Booth JL, Rampton JB. Noninvasive diagnosis of deep venous thrombosis. Arch Int Med 1976; 136:1091-1096. 19. Walsh JJ, Bonnar J, Wright FW. A study of pulmonary embolism and deep leg vein thrombosis after major gynaecological surgery using labelled fibrinogen-phlebography and lung scanning. J Obstet Gynaecol Br Commw 1974; 81:311-316. 20. Schiff MJ, Feinberg AW, Naidich JB. Noninvasive venous examinations as a screening test for pulmonary embolism. Arch Int Med 1987; 147:505 -- Craig F. Feied, MD, FACEP, FAAEM