Indian Prime Minister Manmohan Singh's heart problems couldn't have come at a worse time, with an economic crisis spiraling out of control, terrorism on the rise, and tensions with Pakistan high. The 76-year-old leader underwent heart bypass surgery yesterday and is currently in intensive care, where doctors say he will remain for at least three days. India doesn't have an established procedure for replacing its leader in an emergency. Foreign Minister Pranab Mukherjee has taken over temporarily as acting prime minister, but does not have full responsibilities, as authority over the military rests with the defense minister. Singh previously underwent a heart bypass in 1990 and an angioplasty in 2003, and he's diabetic, raising concerns that his health could affect his ability to function during a crisis period.