Dr. Samuel Lichtenstein cut a 2-inch hole between an elderly man's ribs. Peering inside, he poked a pencil-sized wire up into the chest, piercing the bottom of the man's heart. Within minutes, Bud Boyer would have a new heart valve — without having his chest cracked open. Call it closed-heart surgery. "I consider it some kind of magic," said Boyer, who left the Vancouver, British Columbia, hospital a day later and was almost fully recovered in just two weeks. In Michigan, Dr. William O'Neill slipped an artificial valve through an even tinier opening. He pushed the valve up a patient's...