The hospital's social media team is tweeting facts, photos and videos of the coronary artery bypass graft, also known as CABG. They are also providing information about preventing heart disease and other treatments.
Bypass surgery is done to improve blood flow to the heart, typically after arteries have become blocked with plaque due to coronary artery disease. Surgeons remove a healthy blood vessel — often from the leg —and attach it to the blocked artery.
Sunnybrook likened it to a "road detour" around blocked arteries, with the aim of increasing blood flow to the heart.
At noon, the hospital said the grafts were complete and the heart had resumed beating.
The hospital has said the patient has given permission and are referring to him by his first name, Lou.
Doctors used a potassium mixture to stop Lou's heart, protect and cool it to reduce oxygen needs. Lou is connected to a bypass, or "heart-lung," machine to keep oxygenated blood pumping through his body during the procedure, hospital tweets say.
A surgical photo shows a radial artery harvested from his left arm, one of the patient's two bypass grafts.
Hospital spokeswoman Marie Sanderson says it's hoped the event will educate the public about heart disease. February is billed as heart awareness month.
Ethics of tweeting tragedy?
Followers of #SBheart, which includes teachers and other Canadian hospitals, are commending Sunnybrook for the event.
But Summer McGee, a professor of public health ethics and policy at the University of New Haven, has blogged about the ethics of tweeting live medical procedures.
"Hospitals see dollar signs from great PR," McGee said in an email to CBC News.
"Physicians imagine becoming a social media Sanjay Gupta. But the #epicfail will be for patients: even an outstanding hospital like Sunnybrook cannot possibly prepare patients for tweeting about tragedy. And even when it’s exciting and has a happy ending, hospitals need to keep in mind that reality shows have an editing room … Twitter doesn’t."
CABG, while potentially lifesaving and important for some patients, is needed by only a small proportion of patients who access cardiac care, according to the Canadian Cardiovascular Society. Provinces track wait times for CABG.
The hospital believes it's the first Canadian facility to live-tweet heart surgery.
Elsewhere in 2012, Memorial Hermann Hospital in Houston live-tweeted brain surgery to an audience estimated at 14.5 million. Last fall, a British hospital gave Twitter users a front-row seat for a cataract surgery.
Surgeon featured on CBC
Leading the Sunnybrook surgery is Dr. Gideon Cohen, who was featured in this CBC story you can watch below.