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12-03-2012 | Cardiology | Article

Preemptive anticoagulation benefits selected PE patients


Free abstract

MedWire News: Preemptive anticoagulation may benefit patients with intermediate and high clinical probabilities for pulmonary embolism (PE) even when the diagnostic delay is only a few hours, study findings indicate.

For patients with low pretest probabilities, however, preemptive anticoagulation only appears beneficial when the diagnostic delay exceeds 6 hours, report Marc Blondon (University Hospitals of Geneva, Switzerland) and colleagues in Chest.

The researchers explain that the well-established diagnostic strategy for PE can take several hours to complete, but the utility of anticoagulant treatment during this time remains uncertain.

They therefore built a decision analysis model to evaluate the risks and benefits of anticoagulation with low molecular weight heparin every 12 hours versus no treatment, until confirmation or exclusion of PE.

The model took into account mortality related to untreated and treated PE, mortality due to major hemorrhage, and intracerebral bleeding, and was primarily populated with data from the Computerized Registry of Patients with Venous Thromboembolism (RIETE).

Once the model was built, Blondon and team conducted analyses for different categories of PE probability based on two validated clinical prediction rules: the revised Geneva score (RGS) and the Wells score.

They report that the time to definite diagnosis acted as a critical variable to define the best treatment strategy.

In patients with low, intermediate, and high RGS probabilities, preemptive anticoagulation was superior to no treatment if the diagnostic delay exceeded 6.3 hours, 2.3 hours, and 20 minutes, respectively.

In a hypothetical cohort of 100,000 patients with a low RGS probability, there were five more deaths (five fatal PEs prevented but 10 fatal bleeds induced), and three more intracerebral hemorrhages (ICHs) with anticoagulation than with no treatment.

However, after 6.3 hours, anticoagulation was associated with a lower mortality than no anticoagulation, and its benefit gradually increased with longer delays: 11 deaths were prevented at 12 hours and 62 were prevented at 3 days, with three and 16 induced ICHs occurring at the same time points.

For 100,000 hypothetical patients with a high RGS probability, preemptive anticoagulation prevented 39, 81, 166, and 332 deaths when the diagnostic delays were 3, 6, 12, and 24 hours, respectively, while it produced up to two ICHs. The number needed to treat to prevent one death increased from 2600 at 3 hours to 300 at 24 hours.

Similar results were observed when the Wells score was used as the clinical prediction model. In this case, preemptive anticoagulation was superior to no treatment for diagnostic delays of more than 8.1 hours in the unlikely category and more than 1.7 hours in the likely category.

"Our model suggests that patients with intermediate and high/likely probabilities for PE benefit from preemptive anticoagulation," Blondon and co-authors conclude.

"With a low probability, the decision to treat could rely on the expected diagnostic delay," they add.

By Laura Cowen

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