Noted surgeon Michael Macris has performed more than 500 surgical procedures at Memorial Hermann Hospital in the past five years, but none like the operation he faced Tuesday morning.

As part of American Heart Month, the good doctor offered up the first live online coverage of a beating open-heart surgery in the United States — complete with extremely graphic videos, tweets and up-to-the-minute pictures.

Starting at 7:30 a.m., Macris captured photos and video from a special helmet camera as he performed a coronary bypass on an unnamed 57-year-old man.

Tweeting from the sidelines, Dr. Paresh Patel answered a barrage of questions from online observers who ranged from the medically curious to hospital professionals.

Here's a glimpse of the proceedings. Our more squeamish readers might want to avoid clicking the links.

• 9:15 - Dr. Macris gowning up [video]
• 9:41 - Opening the sternum with saw [video]
• 10:23 - Identifying targets, will place the LIMA's distal end to coronary [twitpic]
• 10:40 - Placing mammary artery distal to the heart [video]

In between procedures, Memorial Hermann tweeted a variety of fast facts. The heart, for example, is a little larger than a human fist, weighs between 7 and 15 ounces, and beats more than 100,000 times each day.