A successful surgery results in a dramatic increase in blood flow to the heart muscle. This increase in blood flow, in turn, reduces the pain, pressure or discomfort (angina) associated with cardiac ischemia. Abnormal heart rhythms (arrhythmias) may develop just after the surgery and may last three to four days, but these abnormal heart rhythms are usually only temporary. In addition, the chest and leg area where incisions were made will likely be slightly sore for at least a few weeks. However, severe pain should be reported to a physician.

 Complications that may arise from bypass surgery include:

Most of these complications are short-term and are not serious, though advanced age and poor overall health may increase their risk and severity. More serious complications that may arise, usually due to the use of the heart-lung machine, include kidney failure, heart attack, stroke or even death. These risks are higher for older patients, people with diabetes and patients with other major health problems. However, it's also important to note that in recent years, the risk of serious complications due to cardiopulmonary bypass has been dramatically reduced due to improved surgical techniques. In one study, researchers found that the rate of serious complications fell by half in the period from the early 1980s to the mid 1990s. In addition, physicians have a number of tools at their disposal to further reduce the risk of post-operative complications. This includes the use of medications, such as aspirin and beta blockers, and very strict blood sugar control.  

One area of complication occurs when grafted arteries become blocked over time and a patient needs a second bypass surgery. This procedure presents greater risks for several reasons. The patient is older and their heart disease has usually worsened. The blood vessels used as grafts in the first surgery are not available to use for the second surgery. In addition, there may be adhesions around the original grafts that make the second surgery more difficult.  Patients should discuss all additional risks with their physician.