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Silent Pulmonary Emboli in Patients with DVT: Time to Screen?
Abstract & Commentary
By Joseph Varon, MD, FACP, FCCP, FCCM, Clinical Professor of Medicine and Professor of Acute and Continuing Care, University of Texas Health Science Center, Houston; Clinical Professor of Medicine, University Texas Medical Branch, Galveston. Dr. Varon receives grant/research support from and serves on the speakers bureaus for The Medicines Group and EKR Pharma.
Synopsis: Asymptomatic pulmonary embolism is quite common among patients with deep venous thrombosis. In many instances in these patients, the pulmonary emboli are located within the central pulmonary arteries.
Source: Stein PD, et al. Silent pulmonary embolism in patients with deep venous thrombosis: A systematic review. Am J Med 2010;123:426-431.
This study was aimed at evaluating the incidence of unsuspected or undiagnosed pulmonary embolism (PE) among patients with deep venous thrombosis (DVT). The primary question that the investigators were addressing was whether or not routine PE screening was necessary for those patients with documented DVT. To accomplish this task, the investigators conducted a systematic review of 28 published studies in PubMed through July 2009. These 28 studies were the result of a literature search that included more than 950 citations. The 28 studies contained specific raw data and detailed description of the methodology utilized to diagnose PE, and documented the absence of symptoms of PE. Criteria for diagnosis of a "silent" PE included the interpretation of a high-probability ventilation-perfusion lung scan, computed tomography (CT), pulmonary arteriography on the basis of either the prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) or non-PIOPED criteria and the absence of pulmonary symptoms and/or signs.
Of 5233 patients with DVT evaluated, 1655 (32%) had evidence of silent PE. Those patients with proximal DVT had a higher incidence of PE. Larger perfusion defects were noted in those patients that had DVT in the pelvic veins or thighs as compared with those with distal thrombi. Moreover, the incidence of recurrent PE was higher in those patients with silent PE (5.1%) as compared to those patients without silent PE (0.6%). A trend for an increased prevalence of silent PE was noted with aging. Those patients younger than age 40 years had silent PE in 14% of the cases as compared to 22% in those aged 40-70 years, and 40% in those older than 70 years of age.
For decades, we have known that PE is commonly found in patients postmortem, in whom this clinical entity was undiagnosed or not suspected antemortem.1 The main question has been: Should we look for PE in every patient with DVT even if they have no pulmonary signs or symptoms?2 The fact is that the treatment of both DVT and PE is the same and conducting additional studies has cost and potential side effect issues.
This well-conducted systematic review is interesting because it shows a high prevalence of silent PE in patients with DVT. With this in mind, the rationale for conducting "additional" pulmonary work-up in patients with documented venous thrombosis (i.e., ventilation-perfusion lung scans, CT, or angiogram) is the fact that patients with DVT tend to have more recurrent PEs when the patients have a "silent" PE (as noted in this study) when compared to those with a first episode of non-silent PE.
That almost one-third of all patients with DVT have a silent PE moves forward the concept of considering pulmonary screening in this patient population. In addition, the decision to admit a patient with a documented DVT to a hospital instead of treating at home may be modified on the basis of these findings.
1. Kistner RL, et al. Incidence of pulmonary embolism in the course of thrombophlebitis of the lower extremities. Am J Surg 1972;124:169-176.
2. Monreal M, et al. Prospective study on the usefulness of lung scan in patients with deep vein thrombosis of the lower limbs. Thromb Haemost 2001;85:771-774.