ISET included several featured abstracts, and we had the opportunity to talk in more detail with the authors.
Abstract Title: Submassive and Massive Pulmonary Embolus: Catheter-Directed Intervention Versus Medical Management?
Abstract Authors: C.T. Hennemeyer, G.J. Woodhead, A.H. Shah, S. Sakla, C.Q. Moffett, S. Black
Interview with Charles T. Hennemeyer, MD, and Gregory J. Woodhead, MD, PhD
Why did you choose to pursue research in this area, and what sets your study on catheter-based therapies apart from what is already in the literature?
Drs. Hennemeyer and Woodhead: Multiple new/novel catheter-based devices have appeared over the last 18 months that allow for more elegant and effective management of submassive/massive pulmonary embolism (PE). We chose to investigate the combination of several new catheter-based technologies, used in combination rather than separately, for the treatment of submassive PE. Perhaps the combination of mechanical aspiration with or without lysis could yield better results than either one alone. Based on early results, we were soon encouraged by what we found and began collecting data.
Can you briefly describe your findings?
Drs. Hennemeyer and Woodhead: One of our primary endpoint measurement tools was pre- and postprocedural right ventricular to left ventricular ratio (RV/LV ratio) measurements on echocardiography, computed tomography angiogram, and in some cases magnetic resonance angiogram. We compared the catheter intervention group against controls who received standard-of-care intravenous heparin alone. We found a significant improvement in preprocedural RV/LV ratios in the catheter-based group. Most patients received a 30-mg tissue plasminogen activator bolus followed by mechanical clot aspiration, and approximately one-third received additional overnight catheter-based lysis.
Tell me about something surprising you encountered while doing this research.
Drs. Hennemeyer and Woodhead: We were surprised by the magnitude of improvement achieved using combination technology, even when the angiographic endpoint was less than complete clot removal. In fact, most cases demonstrated at least some angiographically visible residual clot, yet outcome measures seemed disproportionately positive. This suggests that even with imperfect tools, relatively small gains in clot removal result in large gains in right heart strain.
How might your findings eventually affect clinical practice?
Drs. Hennemeyer and Woodhead: We believe that interventional radiology (IR)-directed catheter thrombolysis of PE is poised for a cardiac catheter moment. Our future research endeavors will focus on how catheter-based interventions affect long-term functional outcomes such as pulmonary vascular reserve and pulmonary exercise tolerance. We believe that if a significant deviation from the natural history can be achieved, catheter-based interventions in the future may become the standard of care, analogous to other common clinical cardiac practices such as coronary angioplasty and stenting.
What future studies would you like to see take place?
Drs. Hennemeyer and Woodhead: First, after a thorough review of the literature, it is clear that there is not a good measure of right heart dysfunction, especially when it comes to determining which patients with PE stand to benefit the most from catheter-directed interventions. The echocardiography value, TAPSE, has shown some promise, but it remains a qualitative measure. Systolic pulmonary artery pressures are highly variable, and RV/LV ratios are also prone to measurement error/variability. Therefore, development of a new gold-standard measurement of right heart dysfunction in the setting of PE is of the utmost importance. Second, while our study was retrospective in design, we are currently enrolling patients in a prospective, randomized controlled trial in order to validate our observations/conclusions.
What are you hoping that attendees take away from your presentation?
Drs. Hennemeyer and Woodhead: Catheter-based pulmonary intervention with additional tools beyond simple lytic devices may offer long-term benefits to patients with PE commonly treated with heparin alone. We hope that other IR practices will continue to experiment with combinations of multiple devices and protocols to achieve better results. However, we would encourage our fellow IRs to experiment with combining catheter-based devices/therapeutics in order to achieve superior results over standard medical management