MedicalResearch.com Interview with:
Nathan Clark, PharmD
Clinical pharmacy supervisor, anticoagulation and anemia management services and
Thomas Delate, PhD
Clinical research scientist
Kaiser Permanente Colorado
MedicalResearch: What is the background for this study? What are the main findings?
Response: Patients with a history of blood clots are commonly prescribed warfarin, an anticoagulant, to decrease the body’s ability to form additional clots. Clinicians typically stop the use of warfarin in patients to reduce the risk of serious bleeding when invasive procedures, such as colonoscopy or orthopedic surgery are scheduled. However, when warfarin interruptions occur, patients are exposed to an increased risk of blood clots three to five days before and five or more days after invasive procedures. Bridge therapy with another, faster acting anticoagulant is often initiated in an attempt to reduce the patients’ risk for developing blood clots during that gap.
Bridging has been a part of standard therapy for venous thromboembolism (VTE) patients undergoing invasive procedures for many years. But only limited data outlining the rates of bleeding and VTE recurrence were available to help clinicians analyze the risks and benefits of bridge therapy.
We examined the electronic medical records of 1,178 patients with VTE who underwent 1,812 invasive diagnostic or surgical procedures between January 2006 and March 2012 that required the interruption of warfarin therapy. Study patients were categorized into three groups based on their annual risk of VTE recurrence without anticoagulant therapy. Within those groups, a total of 555 patients – 28.7 percent of low-risk, 33.6 percent of moderate-risk and 63.2 percent of high-risk patients – received bridging anticoagulant therapy. The 1,257 patients who did not receive bridge therapy interrupted their warfarin use and received no other anticoagulants during the perioperative period. The use of bridge therapy resulted in a 17-fold higher risk of bleeding without a significant difference in the rate of blood clot formation compared to patients who didn’t receive bridge therapy. In addition, there were no significant differences in the rates of blood clot occurrence or death between the bridged and non-bridged patient groups.
MedicalResearch: What should clinicians and patients take away from your report?
Response: This study provides real-world data for clinicians to assess. The rates of bleeding and venous thromboembolism recurrence reported in this study are similar to those that have been reported elsewhere. Multiple researchers have now concluded that bridge therapy may be unnecessary for patients who are at low or moderate risk for recurrent venous thromboembolism. This conclusion has the potential to lead to a major shift in how clinicians deliver a therapy that’s been considered standard for years.
In addition, the recommendation to stop bridge therapy for low or moderate risk venous thromboembolism patients is supported by the study observation of no significant differences in the rates of blood clot occurrence or death between the bridged and non-bridged patient groups.
MedicalResearch: What recommendations do you have for future research as a result of this study?
Response: The results of this study indicate that bridge therapy may be unnecessary and potentially harmful for patients who are at low or moderate risk of developing blood clots during warfarin interruption. However, the benefits of bridge therapy may outweigh the risks for those patients who are at the highest risk of venous thromboembolism recurrence. In this study, high-risk patients were identified as those who had a greater than 10 percent risk per year of developing a blood clot during the perioperative period. Further research is needed to identify the patient and procedure-related characteristics that place patients at highest risk for venous thromboembolism recurrence where bridge therapy during warfarin interruption may be beneficial.
Clark NP, Witt DM, Davies LE, et al. Bleeding, Recurrent Venous Thromboembolism, and Mortality Risks During Warfarin Interruption for Invasive Procedures. JAMA Intern Med. Published online May 26, 2015. doi:10.1001/jamainternmed.2015.1843.
Nathan Clark, PharmD Clinical pharmacy supervisor, anticoagulation and anemia management services and, Thomas Delate, PhD Clinical research scientist, & Kaiser Permanente Colorado (2015). Anticoagulation Bridge Therapy May Be Unnecessary For Low Risk Venous Thromboembolism Patients MedicalResearch.com