Dr. Starling and his associates did note the deposition of fibrin and denatured protein around the inflow bearing, which could narrow the inflow pathway, "increasing shear stress on the red cells and, if the deposition is large enough, decreasing the ability of the pump to unload the left ventricle." But it remains to be seen whether this or other factors played a role.
"Further investigation of predisposing patient and device factors and preventive and therapeutic strategies are urgently needed to resolve this important safety issue," the investigators said.
They added that a fourth cardiology center, the University of Pennsylvania, Philadelphia, found a similar pattern in a preliminary analysis that was reported as the article went to press. In that report on 150 HeartMate II LVADs implanted in 148 patients between November 2005 and September 2013, there were 15 thrombotic events. "Similar to the findings in our study, the event rate has increased abruptly and unexpectedly, with a rate of confirmed thrombosis that continues to rise," Dr. Starling and his associates said.
Dr. Starling reported ties to Thoratec and HeartWare, and his associates reported ties to Thoratec, HeartWare, Abiomed, and Syncardia.