Database study could open up field for catheter-directed PE treatment research

Osman Ahmed

A database study titled ‘Unplanned 30-day readmissions and in-hospital outcomes for the management of submassive and massive acute pulmonary embolism: Catheter-directed versus systemic thrombolysis’ has produced results that could provide some of the evidence base for preference of catheter-directed over systemic thrombolysis in treating the more severe cases of pulmonary embolism (PE).

Osman Ahmed, who is author of the study and associate professor of radiology at the University of Chicago (Chicago, USA), met with Interventional News at the Society of Interventional Radiology (SIR) 2022 Annual Meeting (11–16 June, Boston, USA) to discuss his research. The abstract was also presented by Waseem Wahood (Dr Kiran C Patel School of Allopathic Medicine, Fort Lauderdale, USA) during the meeting’s pulmonary embolism session.

Ahmed began by outlining his clinical background and what led him to pursue this research on PE treatment. Clinically, he explained, one of his main interests is venous thromboembolism, but being the co-chair of the SIR Comparative Effectiveness Research Committee—an arm of the society whose goal is to develop “evidence-based data to compare interventional radiology [IR] services and procedures with their medical and surgical alternatives”—he wanted also to incorporate this area of focus into a study.

The first question posed to Ahmed was regarding the existing PE treatment landscape and what determines whether a given patient will receive catheter-directed or systemic thrombolysis. Ahmed dubbed this “a great question” to which the answer lies in the fact that “PE in general is a heterogenous disease, with different levels of severity”—massive, submassive and low-risk. “Fortunately,” he continued, “most patients are low risk”. Expanding on this, Ahmed specified how it is the massive and submassive patients who “require hospitalisation and often follow-up intervention,” which is, “where IR comes into play.”

One of the key advantages of the catheter-based approach is that it is minimally invasive, Ahmed pointed out, however, “most society guidelines [for PE treatment] outside of IR […] do not recommend what we do.” Ahmed asserted his nonetheless widely shared belief that catheter-based thrombolysis is “safe.” Studies carried out before his, while smaller, showed “a similar rate of effectiveness” between catheter-based and systemic treatments, but the former saw “lower rates of bleeding.” Ahmed referred to this existing, promising evidence as motivation for doing his database study.

Asked then why he choose to approach the study from the angle of side effects, Ahmed offered by way of explanation the “very high chance of recurrence” with PE. “If you survive [the rate can be between] 30 and 40%”. Furthermore, Ahmed underlined, the nature of the treatment means that “if you give too much of the [PE] medication, the risk of bleeding is high, but too little and you do not clear the PE.”

Bleeding was “a big problem” in the patients from the database who had received systemic over catheter-based treatment, which often resulted in rehospitalisation—problematic in that it depletes resources and beds for patients with other conditions, Ahmed highlighted.

Moving on to discuss the results of his study—whether or not they were as expected—Ahmed conveyed how he had been surprised by how they were “very, very consistent with what we thought”. This was the case for “every metric [and even with] propensity matching.” Ultimately, rates of intra-abdominal and intracranial bleeding, as well as hospital readmissions were “all one to two times higher with systemic thrombolysis.” Ahmed acknowledged that it was an outcome that “almost felt too good to be true,” especially since the patients at higher risk of bleeding are often those who receive catheter-directed treatment. “If we were going to see no difference,” Ahmed admitted, he would have expected it to be as a consequence of the sickest patients receiving this less evidence-based treatment.

Finally, conversation turned to next steps regarding the picture of PE treatment and research in the future. “Trials […] take a lot of time and cost a lot of money,” Ahmed emphasised, which, in turn, accentuates “the beauty” of his study, conducted with a 36,000-strong patient base. “We really need [more] trials,” Ahmed affirmed, expressing his hope that the promising results his research has yielded will “pave the way” for increased government funding assigned to future PE research.

Yet, of note, is the fact that even without these prospective trials and the inclusion of catheter-directed thrombolysis in the majority of PE treatment guidelines, there has been, of late, a “tenfold increase” in the recourse to catheter-directed treatment. Ahmed ended on the following note—”We are hoping that [our study] helps provide the framework” to include catheter-directed thrombolysis in guidelines more widely.


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