Looking for Asymptomatic Pulmonary Embolism in Patients with Deep Vein Thrombosis: Is It the Right Practice?

Abstract

The systematic review by Stein et al1Stein P.D. Matta F. Muzammil H. et al.Silent pulmonary embolism in patients with deep venous thrombosis: a systematic review.Am J Med. 2010; 123: 426-431Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar proposing using ventilation-perfusion (V/Q) scanning looking for asymptomatic or silent pulmonary thromboembolic disease in patients presenting initially with lower limb deep venous thrombosis raises concern. Although not doubting the concurrent nature of disease, the first question to be asked is whether the significance, nature, severity, or outcome from identifying concurrent pulmonary thromboembolism among patients managed as ambulatory deep venous thrombosis schemes is actually different from that presenting overtly with pulmonary thromboembolism? In a previous audit at this center,2Iyer H.V. Fildes E. Srinivasan K.S. Moudgil H. Risks of pulmonary thromboembolism associated with ambulatory management of clinically proven deep vein thrombosis.Eur Respir J. 2005; : A4455Google Scholar of 421 patients diagnosed with deep venous thrombosis (proximal or distal) over a 4-year period to September 2004, only one re-presented while on anticoagulation (17 days into scheme) and was then proven to have a pulmonary thromboembolism. Second, although UK guidelines propose computed tomography pulmonary angiography (CTPA) as initial imaging for nonmassive pulmonary thromboembolism, they do accept V/Q scanning provided that, among other requirements, a nondiagnostic result is always followed by further imaging.3British Thoracic Society Standards of Care Committee Pulmonary Embolism Guideline Development GroupBritish Thoracic Society guidelines for the management of suspected acute pulmonary embolism.Thorax. 2003; 58: 470-484Crossref PubMed Scopus (650) Google Scholar With this latter direction in mind, we know that 65% of patients undergoing V/Q scan will have an intermediate probability,4Gottschalk A. Sostman H.D. Coleman R.E. et al.Ventilation-perfusion scintigraphy in the PIOPED study Part II. Evaluation of the scintigraphic criteria and interpretations.J Nucl Med. 1993; 34: 1119-1126PubMed Google Scholar needing additional imaging. Simply adopting CTPA for this adds consequences of added radiation, including that prompted by incidental and alternative findings, such as mediastinal lymphadenopathy, necessitating further follow-up scans and repeat exposure. Carcinogenicity due to ionizing radiation in patients receiving in excess of 50 mSv is reported and, although dose calculation can be quite complex as different organs will absorb radiations differently, a 64-slice CTPA can deliver a dose of up to 50-80 mSV to the breast tissue in females.5Amis Jr, E.S. Butler P.F. Applegate K.E. et al.American College of Radiology white paper on radiation dose in medicine.J Am Coll Radiol. 2007; 4: 272-284Abstract Full Text Full Text PDF PubMed Scopus (695) Google Scholar, 6The International Commission on Radiological ProtectionManaging patient dose in computed tomography: a report of the International Commission on Radiological Protection—ICRP publication 87.Ann ICRP. 2000; 30: 7-45Google Scholar, 7Einstein A.J. Henzlova M.J. Rajagopolan S. Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography.JAMA. 2007; 298: 317-323Crossref PubMed Scopus (1207) Google Scholar As it is the consequence of concurrent pulmonary thromboembolism that we are concerned about, what is required is a more practical approach incorporating pretest probability scores for pulmonary thromboembolism and, although less specific, possibly incorporating cardiac biomarkers as a measure of cardiovascular strain when first diagnosing deep venous thrombosis. This then draws us away from the systematic review1Stein P.D. Matta F. Muzammil H. et al.Silent pulmonary embolism in patients with deep venous thrombosis: a systematic review.Am J Med. 2010; 123: 426-431Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar and screening of every patient with deep venous thrombosis. Silent Pulmonary Embolism in Patients with Deep Venous Thrombosis: A Systematic ReviewThe American Journal of MedicineVol. 123Issue 5PreviewTo determine, by systematic review of the literature, the prevalence of silent pulmonary embolism in patients with deep venous thrombosis. Full-Text PDF The ReplyThe American Journal of MedicineVol. 124Issue 1PreviewWe appreciate the comments of Ahmad, Srinivasan, and Moudgil. Certainly there are a variety of valid approaches to the problem of silent pulmonary embolism. We called attention to the 32% prevalence of silent pulmonary embolism in patients with deep venous thrombosis and suggested consideration of routine screening.1 Advantages would be a baseline for comparison with future imaging studies if the patient subsequently were to become symptomatic. A baseline image would prevent a misdiagnosis of failure of therapy. Full-Text PDF