A troubled heart pump that has now been linked to 49 deaths and dozens of injuries worldwide will be allowed to remain in use, despite the Food and Drug Administration’s decision to issue an alert about the risk that it could puncture a wall of the heart.

The tiny Impella pumps, about the width of a candy cane, are threaded through blood vessels to take over the work of the heart in patients who are undergoing complex procedures or have life-threatening conditions.