How concerned is Wall Street about St Jude Medical's ($STJ) heart rhythm devices? Very, especially since physicians might now think twice about using the company's heart devices (bear in mind, there's a $6.5 billion worldwide market for implantable defibrillators at stake). "I stopped using Durata months ago. I stopped using Riata years ago," Reuters quotes one doctor as saying--and those words can't make the company feel much better. "People are wondering, is there more to this story? When you see such a vigorous defense, you wonder what's evoking this? Why are they fighting people who are raising questions? This could leave lasting reputational damage," said Dr. Harlan Krumholz, a cardiologist at the Yale School of Medicine. Analysis