Integrated Approach to Diagnosis of Pulmonary Embolism in Objective-C

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An integrated approach to diagnosis of PE uses the clinical likelihood of venous thromboembolism derived from a clinical prediction rule (Table 9 17) along with the results

Table 9 17 Clinical prediction rule for pulmonary embolism (PE)

Variable Clinical symptoms and signs of deep venous thrombosis (DVT) (leg swelling and pain with palpation of deep veins) Alternative diagnosis less likely than PE Heart rate > 100 beats/min Immobilization for more than 3 days or surgery in previous 4 weeks Previous PE or DVT Hemoptysis Cancer (with treatment within past 6 months or palliative care) Three-tiered clinical probability assessment High Moderate Low Dichotomous clinical probability assessment PE likely PE unlikely Points 30

Data from Wells PS et al Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: increasing the models utility with the SimpliRED D-dimer Thromb Haemost 2000 Mar;83(3):416 20

3 Match results in the following table Clinical suspicion for PE by clinical probability assessment HIGH High probability STOP Diagnosis established Treat for PE MODERATE STOP Diagnosis established Treat for PE LOW Diagnosis likely (56% in PIOPED I, but small number of patients) Treat for PE or evaluate further with LE US or CT-PA

Adapted, with permission, from The PIOPED Investigators Value of the ventilation/perfusion scan in acute pulmonary embolism: results of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) JAMA 1990 May 23 30;263(20):2753 9 PE, pulmonary embolism; LE US, lower extremity venous ultrasound for DVT; CT-PA, helical CT pulmonary angiography

of diagnostic tests to come to one of three decision points: to establish venous thromboembolism (PE or DVT) as the diagnosis, to exclude venous thromboembolism with sufficient confidence to follow the patient off anticoagulation, or to refer the patient for additional testing An ideal diagnostic algorithm would proceed in a cost-effective, stepwise fashion to come to these decision points at mini mal risk to the patient The standard V/ Q scan based algorithm (Table 9 18) has been replaced in most North American centers by a rapid D-dimer and helical CT pulmonary angiography based diagnostic algorithm (Fig ure 9 1) The V/ Q scan remains useful in many patients, especially those who are not able to undergo CT pulmonary angiography (eg, those with renal failure), but there is a growing evidence to support the CT-based approach In the rigorously conducted Christopher Study, the incidence of venous thromboembolism was only 13% and fatal PE occurred in just 05% of persons monitored for 3 months off anticoagulation therapy after objective, validated tools

for clinical assessment, quantitative rapid D-dimer assays and a negative helical CT pulmonary angiography The incidence of PE following a negative evaluation by these three means is comparable to that seen following negative pulmonary angiography

Venous thromboembolism is often clinically silent until it presents with significant morbidity or mortality It is a prevalent disease, clearly associated with identifiable risk factors For example, the incidence of proximal DVT, PE, and fatal PE in untreated patients undergoing hip fracture surgery is reported to be 10 20%, 4 10%, and 02 5%, respectively There is unambiguous evidence of the efficacy of prophylactic therapy in this and other clinical situations, yet it remains underused Only about 50% of surgical deaths from PE had received any form of preventive therapy Tables 9 19 and 9 20

Concern for PE Dichotomous Clinical Probability Assessment PE Unlikely Rapid quantitative ELISA D-dimer assay Negative Positive High quality, normal study PE excluded Search for alternative diagnoses Follow off anticoagulation PE Likely Helical CT-PA Indeterminate study for PE Findings of PE Diagnosis established Treat for PE

Figure 9 1 D-dimer and helical CT-PA based diagnostic algorithm for PE CT-PA, CT pulmonary angiogram; PE, pulmonary embolism; ELISA, enzyme-linked immunosorbent assay; VTE, venous thromboembolic disease; LE US, lower extremity venous ultrasound for deep venous thrombosis; PA, pulmonary angiogram (Reproduced, with permission, from van Belle A et al: Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography JAMA 2006;295:172)

provide overviews of strategies for the prevention of venous thromboembolism Options for therapy begin with mechanical devices such as graduated-compression stockings and intermittent pneumatic compression The latter improves venous return and may increase endogenous fibrinolysis by stimulating the vascular endothelium Standard pharmacologic therapy in medical patients is low-dose unfractionated heparin, 5000 units subcutaneously every 8 12 hours Low-molecular-weight (LMW) heparins are more expensive but have several advantages compared with unfractionated heparin: better bioavailability, once- or twice-daily dosing, and a lower incidence of heparin-associated thrombocytopenia In high-risk surgical patients, LMW heparins can be administered without the need for coagulation monitoring and dose adjustments, as would be the case with unfractionated heparin