by Pauline Mayer
At the Society for Interventional Radiology’s 36th Annual Meeting, interventionalists gathered to hear several informative presentations focused on deep venous thrombosis (DVT) and pulmonary embolism (PE). Dr. William Kuo, assistant Professor and Fellowship Director, Division of Vascular and Interventional Radiology at Stanford University Medical Center provided updates on DVT and PE to a large audience of attendees from around the world.
The standard of care for PE has been anticoagulation therapy. Nevertheless, many specialists are of the strong opinion that although these drugs are used to prevent a clot from getting bigger, they do not dissolve the clot or restore blood flow to the vein. Dr. Kuo is one of those experts holding this opinion.
Dr. Kuo’s initial success with this technique – used on an ER patient who had collapsed from a massive PE – set him on a three-year mission to design and implement studies to reveal the safety and effectiveness of catheter-directed therapy or catheter-directed thrombolysis for massive blood clots in the lungs. After additional research, he later published his findings in the November 2009 issue of the Journal of Vascular and Interventional Radiology.
VM: You wrote an article on a meta-analysis using catheter-directed thrombolysis to treat PE. What were the highlights & your conclusions?
WK: Our research team discovered 594 patients in 18 countries who had undergone this therapy between 1990 and 2008. after statistically analyzing the data, they found that not only was the treatment effective, but it also appeared much safer than injecting the high-dose thrombolytic drug systemically or directly into the bloodstream where it can circulate throughout the body and cause dangerous bleeding in up to 20 percent of patients.
By targeting blood clots directly, the catheter-based procedure was associated with only a 2.4 percent chance of major complications, and the procedure was life-saving in 8.5 percent of the 594 patients dying from PE. (The study has prompted Kuo and his coauthors to call for making the procedure a first-line treatment option for pulmonary embolism.)
VM: Do you see the method of treating PE changing?
WK: For massive PE, there is now very strong global evidence that catheter-directed therapy should play a major role in the early treatment of these critically ill patients. The complications from this procedure appear to be much lower than the standard medical treatment, which is systemic Tissue-Plasminogen Activator (TPA). In centers with the appropriate expertise, catheter-directed therapy could be considered as the treatment of choice in massive PE patients.
VM: What are the trends?
WK: Due to the evidence that has accumulated worldwide, more and more interventionalists are learning to use catheter-based intervention to treat acute massive PE, and there will continue to be a trend of using catheter-directed thrombolysis as a life-saving procedure.additionally, there is a potential to extend treatment criteria from massive PE patients (hemodynamic shock) to treating patients with sub PE (i.e. right heart strain without shock).
Eventually, as more data is accumulated, the treatment of choice for many patients with sub-massive PE could become catheter-directed thrombolytic infusion.
VM: Is there a need for increased awareness of PE and new methods of treatment?
WK: Yes, there certainly is. acute PE is a serious life-threatening condition. as more interventionalists gain expertise in treating acute PE, there will naturally be growing awareness throughout the rest of the medical community, but interventionalists must drive this movement by educating themselves on catheter-based PE treatment and by making themselves available to perform it whenever urgently needed.
VM: How do you propose specialists educate the lay medical community on PE and new treatments?
WK: First, interventional specialists must educate them-selves on pulmonary embolism. They need to understand the different types of acute PE from simple to sub massive to massive, and they need to understand the pathophysiology of acute PE. For those interventionalists who are already comfortable with treating DVT, it is a natural progression to learn more about using their catheter-based skills to treat acute PE.
Specialists should educate their referring colleagues and show them the existing data supporting endovascular therapy for acute PE. They should let everyone know that the same principles used to perform catheter-directed intervention in the periphery can also be used in the central circulation to treat acute PE. For patients dying from a massive PE, referring clinicians should understand that CDT can be used as a life-saving procedure not only for patients with contraindications to systemic TPA but also in those who have already failed systemic TPA treatment.
VM: What are the additional risks of endovascular therapy?
WK: From our study of 594 patients, the procedural risks of endovascular therapy were actually low (2.4%), and the vast majority of complications were directly attributed to a specific rheolytic thrombectomy device. If this device was avoided, risks such as bradyarrhythmia, heart block, hemoglobinuria, hemoptysis, and procedure-related death would be drastically diminished.
VM: Are their any new technologies mitigating these risks?
WK: Based on our global meta-analysis, the elimination of potentially harmful devices will immediately mitigate procedural risks.There is also potential for risks to decrease even further if PE patients are identified and treated earlier, meaning when they are diagnosed with sub massive PE before they progress to massive PE.
The reason is that these patients could undergo gentle catheter infusion placement for thrombolytic infusion and avoid the aggressive mechanical maneuvers required for treating massive PE. Specific catheters and technologies aimed at treating sub-massive PE more effectively are currently under development.