Affiliations: Stanford University Medical Center, Stanford, CA,
Correspondence to: William T. Kuo, MD, Department of Radiology, Stanford University Medical Center, 300 Pasteur Drive, H-3651, Stanford, CA 94305-5642; e-mail: email@example.com
We read with great interest Dr. Samuel Goldhaber’s comments1regarding percutaneous mechanical thrombectomy (PMT) for acute pulmonary embolism (PE). Dr. Goldhaber describes PMT as a “double-edged sword,” citing the case report by Kumar et al2as a highlighted example. In that case, hemolysis was secondary to the AngioJet device (Possis Medical; Minneapolis, MN), which caused hypotension and “hematuria.” Hemolysis, hemoglobinuria (not hematuria), and bradyarrhythmia are the expected side effects from rheolytic thrombectomy and have been known for many years.3–4 Consequently, we believe the AngioJet should not have been used for PE lysis.
Dr. Goldhaber mentions that PMT catheters can perforate vascular structures and cause massive distal embolization. In spite of these fears, the rates of major complications have been extremely low when using catheter-based methods. The systematic review published by Skaf et al5 analyzed 348 cases of catheter-directed intervention (CDI), reporting only one episode (0.3%) of perforation (right ventricle) that was secondary to the Greenfield catheter, a device no longer manufactured. In the same meta-analysis,5 the rate of major hemorrhagic complications was only 2% (all groin venipuncture sites). Distal massive embolization was not even reported as a recognized complication, and overall clinical success was approximately 80%.
Dr. Goldhaber states that controlled trials for PMT are unrealistic, with no appropriate comparison group, and that first-adjunct treatment to heparin should be IV tissue plasminogen activator (tPA). We question those assumptions because catheter-directed intervention may prove more effective and safer than systemic tPA. In our experience, presented at CHEST 2007, CDI was successfully used not only in PE patients with failed systemic tPA, but also as a first adjunct in patients with contraindications to systemic lysis, sparing them the risks of IV tPA.6The estimated risk of major hemorrhagic complications from systemic tPA is 5%.7 If these statistics hold true, then IV thrombolysis may be the true double-edged sword. Thus, a randomized trial comparing systemic tPA to a standardized CDI protocol is warranted.
We are pleased that Dr. Goldhaber will assume a leadership role in establishing a global registry for catheter-directed treatment of PE, and we offer our full support from the Stanford Division of Vascular and Interventional Radiology. Although more research is needed, the best available evidence suggests that CDI is a safe and highly effective treatment.5 Indeed, we believe catheter-directed intervention is not a double-edged sword but rather a shining saber in the fight against PE.
The authors have no conflicts of interest to disclose.
The author has no conflict of interest to disclose.
Kuo et al write elegantly about percutaneous mechanical thrombectomy (PMT). In my recent editorial,1 I called it a “double-edged sword,” but they extol the procedure as “a shining saber.” I think they are polishing their equipment, and the reflection is dazzling. That is certainly the situation when PMT does what is intended. Success begets success. However, a dazzling saber sometimes causes glare, which in turn can challenge visibility.
The Stanford Group does not like the AngioJet device (Possis Medical; Minneapolis, MN) for PMT. However, many interventionalists do use the AngioJet device because of their familiarity with it and because of sporadic but dramatic “saves” of patients who otherwise appear doomed to succumb to acute pulmonary embolism (PE). Nevertheless, all of us interested in PMT are operating in a data-free zone. For this reason, the Venous Thromboembolism Research Group and the North American Thrombosis Forum (www.NATFonline.org) will join forces with the Stanford Division of Vascular and Interventional Radiology and all who wish to move the field forward. The initial step will be a collaborative international centralized registry.
Despite the problems with PMT, thrombolysis for PE may be equally or even more problematic. Thrombolysis is certainly not by itself a panacea for all PE patients who require more aggressive intervention than anticoagulation alone. At Brigham and Women’s Hospital, we found that of 104 patients receiving PE thrombolysis who were not enrolled in a clinical trial, 19% had major hemorrhagic events.2 Therefore, I agree with Kuo et al that, eventually, a randomized trial of PMT vs thrombolysis should be undertaken. But for now, we must teach each other optimal PMT techniques and develop better equipment to facilitate PMT.
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