More on bridging anticoagulation

I appreciated your article “Three hot topics in perioperative medicine” (December 2015), but I wanted to raise an issue that we overlook when considering bridging patients with mechanical valves.

I recently had a preoperative consult for a patient with a mechanical aortic valve undergoing lumbar laminectomy. When I was asked about anticoagulation, I found two standards of care: one shared by the hospitalists and cardiologists, the other by the thoracic surgeons.

As hospitalists, we focus on the stroke risk, and we find that the ACC/AHA guidelines do not recommend bridging for this patient’s type of aortic valve. But our pharmacist wanted me to first talk with the thoracic surgeons before he would sign off on the coumadin hold order.

The surgeons were not concerned with stroke risk but with valve thrombosis. I was unaware of the severity of this complication, and I can find few data on its frequency. Only small studies exist to show safety in not bridging for this indication.

If the leaflets of the valve clot, the patient needs an emergent valve replacement with a very high mortality rate. As a result, all our surgeons bridge all patients with mechanical valves, regardless of valve position or the type of valve. This complication is almost completely missing from any discussion of bridging in the literature. Clearly, further studies are needed.

Thomas Steele, MD Corvallis, Ore.

Hugo Quinny Cheng, MD, director of medicine consultation, University of California, San Francisco, responds: While a serious complication, clinically important prosthetic valve thrombosis (PVT) appears to be a rare event. A retrospective study of 440 patients with St. Jude prosthetic mitral valves found a 0.2% thrombosis incidence per patient-year. PVT risk appears to be lower with modern valve designs and aortic valve replacements. Thus, PVT risk factors mirror those for embolic complications of prosthetic valves. PVT incidence is also higher immediately after implantation, which may be why thoracic surgeons are particularly concerned about this complication and may overestimate the long-term risk.

Reference: Isolated mitral valve replacement with St. Jude medical prosthesis: long-term results: a follow-up of 19 years. Circulation. 2001;103(11):1542.