Edwards Lifesciences (NYSE:EW) warned doctors about the low risk of burst balloons during implantation of its Sapien 3 Ultra replacement heart valve, cautioning physicians to closely follow the instructions for use to avoid the problem.

The Irvine, Calif.-based medical device maker’s latest iteration of its transcatheter aortic valve replacement won CE Mark approval in the European Union in November 2018; FDA approval followed in December of that year.

In an undated field advisory, Edwards said it received an unspecified number of reports of burst balloons with the Sapien 3 Ultra “which have resulted in significant difficulty retrieving the Sapien 3 Ultra delivery system into the sheath and withdrawing the system from the patient.”

Edwards said the the complaint rate for balloon burst is about 1.0% “based on the limited experience with the device. Of those reports, approximately 0.5% resulted in clinical implications for the patient, the company said, including difficulty removing the valve’s delivery system, vascular injury, bleeding and/or the need for surgical intervention.

“Valve deployment was successful in these cases. Following investigations into these events, Edwards has not identified any evidence of devices that did not conform to specifications,” the company said.

Its investigation turned up two factors influencing balloon bursts, excess inflation volume and fast inflation conditions, both of which are addressed in the Sapien 3 Ultra instructions for use. The TAVR device’s balloon is designed for slow and continuous inflation and a three-second hold once fully inflated, with prescribed volumes for valve deployment.

An additional warning is slated to be added to the device’s IFU, the company said, cautioning that failure to slowly inflate to the prescribed volumes “may result in balloon rupture, difficulty retrieving the delivery system, and may require subsequent conversion to surgical intervention,” Edwards said in the letter.

“Further investigation has also identified a new method for retrieving a burst Sapien 3 Ultra balloon through the sheath. It should be noted that this technique may not resolve all retrieval scenarios,” the company said, noting that it’s updating its training materials to include the method.