Patients with a mechanical heart valve constitute a challenging population at extreme thromboembolic risk, but Dr. Vahanian offered a comforting prediction: "We are nearing the end of the era of mechanical prosthetic valves," he declared. "Patients are getting older, bioprostheses are getting better, and valve repair techniques are improving."
Dr. Harry R. Buller took issue with Dr. Van de Werf’s blanket prediction that the factor Xa inhibitors will prove similarly unsafe and ineffective in patients with mechanical valves, as was dabigatran.
"We still need to find that out. One molecule of factor Xa generates about 1,000 thrombin molecules, so inhibiting coagulation at the level of Xa might actually be effective. What you see with dabigatran is inhibition at the very last stages of the whole coagulation cascade, when there are millions and millions of molecules of thrombin. That’s quite difficult. If you do it higher up in the cascade it might work," argued Dr. Buller, chairman of the department of vascular medicine at the Academic Medical Center, Amsterdam.
"Would you take that risk?" challenged Dr. Van de Werf.
"I know there are people taking that risk. I love studies; I would study it," Dr. Buller replied.
Session cochair Dr. Keith A.A. Fox of the University of Edinburgh posed a provocative question to Dr. Van de Werf: "Would you extrapolate these RE-ALIGN data to a patient in atrial fibrillation with a bioprosthetic valve?"
"It’s a difficult question," Dr. Van de Werf replied. "In principle, you could give one of the novel anticoagulants approved for atrial fibrillation, including dabigatran, because it is assumed there is no indication for oral anticoagulation for the bioprosthetic valve. I’m not saying you necessarily should do that. If the patient is doing well on warfarin, I don’t see the need to switch to one of the new anticoagulants."
RE-ALIGN was supported by Boehringer Ingelheim. Dr. Van de Werf reported receiving research grants and speakers’ fees from the company. Dr. Buller, Dr. Fox, and Dr. Vahanian reported no relevant financial interests.