According to ABC News, "Clinton underwent a procedure at Columbia Presbyterian Hospital...George Stephanopoulos says the procedure may have been for a stent." President Clinton, who is now 63 years old, had quadruple bypass surgery at the same hospital in September 2004. My thoughts are with him and his family for a fast recovery.
UPDATE: Steve Clemons points out, "President Obama is still greatly appreciated and admired around the world -- but the two places on the globe where Clinton is loved more than Obama and where the President should consider applying the unique skills of Bill Clinton are in North Korea and Israel/Palestine matters." He's also been working hard on Haiti and his Foundation. In general, Clinton has been a superb former President.
UPDATE #2: USA Today reports, "Following a visit to his cardiologist, [Clinton] underwent a procedure to place two stents in one of his coronary arteries."