In reply: Submassive pulmonary embolism (December 2016)

We thank Dr. Katyal for his thoughtful comments.

Dr. Katyal points out that the grade of recommendation for thrombolysis in patients with massive pulmonary embolism was upgraded from 2C to 2B in the 2016 American College of Chest Physicians (ACCP) guidelines¹ compared with the 2012 guidelines² that we cited. The upgrade in this recommendation was owing to 2 small trials and 1 large randomized controlled trial that included patients with submassive pulmonary embolism.^3–5 Interestingly, these 3 studies led to an upgrade in the level of recommendation for thrombolysis in the treatment of massive pulmonary embolism, perhaps more from a safety aspect (in view of the incidence of major bleeding vs mortality). Regardless, Dr. Katyal is correct in highlighting that the new 2016 ACCP guidelines now give a grade of 2B for thrombolytic therapy in the treatment of massive pulmonary embolism. These guidelines had not been published at the time of submission of our manuscript.

Dr. Katyal is also correct that patients were not required to have right ventricular dysfunction to be enrolled in the MOPETT trial.³ As we pointed out, “Only 20% of the participants were enrolled on the basis of right ventricular dysfunction on echocardiography, whereas almost 60% had elevated cardiac biomarkers.”⁶

Regarding catheter-directed therapy, patients who received low-dose catheter-directed alteplase were also concurrently anticoagulated with systemic unfractionated heparin in the Ultrasound-Assisted, Catheter-Directed Th rombolysis for Acute Intermediate-Risk Pulmonary Embolism (ULTIMA) trial.⁷ Th e ULTIMA trial authors commented that unfractionated heparin was started with an 80-U/kg bolus followed by an 18-U/kg/hour infusion to target an anti-factor Xa level of 0.3 to 0.7 μg/mL, which is considered therapeutic anticoagulation. Th e investigators in the SEATTLE II trial⁸ continued systemic unfractionated heparin but targeted a lower “intermediate” anticoagulation target (an augmented partial thromboplastin time of 40–60 seconds), so these patients weren’t completely without systemic anticoagulation either. At our institution, the current practice is to target an anti-Xa level of 0.3 to 0.7 μg/mL in patients receiving catheter-directed therapy for large-volume pulmonary embolism.

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