Patients who were implanted with Thoratec Corp's HeartMate II heart pump may be at a higher risk of developing dangerous blood clots.
Medical researchers also found the clots were occurring closer to the time of implantation than they had in the past, Reuters reported.
HeartMate II is a left ventricular assist device (LVAD) that is used in patients that are waiting for a heart transplant or cannot get one at all.
The rate of thrombosis (a blood clot that forms in a blood vessel) associated with the pump was only 2.2 percent before March of 2011, but by January of 2013 the rate had risen to 8.4 percent, MedPage Today reported.
"We recognize that LVADs provide life-sustaining treatment for many patients with advanced heart failure," the researhcers wrote in the study published in the New England Jounral of Medicine, MedPage Today reported."However, recommendations for LVAD therapy should account for this updated risk-benefit profile."
The researchers are yet to discover what is causing the increasing clot incidents.
"To our knowledge, they have looked carefully but haven't pinpointed anything specific," Randall Starling, MD, MPH, of the Cleveland Clinic, told MedPage Today. "So we just don't know [the reason] at this point."
In this case thrombosis was defined as a clot found on or in the device during heart transplant or pump replacement, Reuters reported.
Overall, the team found 72 instances of thrombosis in 66 of the patients. The death rate of those that were diagnosed with thrombosis but did not receive an emergency heart transplant or pump replacement was 48 percent. Those who were treated immediately had a death rate of 10 percent.
"The takeaway to me is that physicians and patients need to realize that this is a known adverse event that can occur with the pump that appears to occur more frequently than was originally recognized," Starling said, Reuters reported.
"When you see early signs of pump thrombosis, hopefully you can abort it or stabilize it," Starling said. "If there are signs and symptoms of recurrent heart failure from suspected pump thrombosis, you intervene quickly if your index of suspicion is high."
