Medical devices including catheters, defibrillators, heart stents and artificial joints will carry unique identification numbers under a plan proposed by the U.S. Food and Drug Administration to improve patient safety. The program would apply to most medical devices and cost as much as $68.4 million a year, according to a pending rule proposal made public on the FDA’s website today. The plan would be implemented over seven years to allow companies, doctors, hospitals and regulators to prepare and spread out the costs.