1.26 million Americans will have a heart attack this year, according to the American Heart Association. Coronary artery disease or blockages in the arteries of the heart cause heart attacks. Heart bypass surgery reestablishes blood flow to the heart muscle. Bypass surgery is required when the patient has multiple areas of blockages or coronary arteries that are too small for stents. Surgeons use the left internal mammary artery from the chest wall and veins from the legs to bypass the blockages to the heart. As with any operation, heart bypass surgery can have complications. Smokers, the elderly and diabetics are at higher risk of complications.
Chest Wall Infection
The surgeon makes a large incision from the top of the breast bone to the bottom to gain access to the heart. Following the incision, he cuts away the muscles attached to the sternum and then cuts the sternum in half, lengthwise, with a surgical saw. After exposing the heart, the surgeon frees the left internal mammary artery from the chest wall for use on the heart. The risk of infection is high when the blood flow to the chest wall is disrupted in this manner, particularly for diabetic patients. Chest wall infection is a rare but potentially life-threatening complication. Occasionally, if the infection does not respond to long-term antibiotics, the sternum must be removed.
Organ Failure
The surgeon must stop the heart and drain it of blood in order to operate on it. She uses the cardiopulmonary bypass machine to obtain a bloodless field. Plastic tubing inserted into the aorta and the right atrium drains blood from the patient to the machine. The machine oxygenates the blood and returns it to the patient as the surgeon works. The machine adds solutions to the blood, such as heparin, which prevents clots from forming. Perfusing the body this way exposes the red blood cells to trauma and this incites an inflammatory response which can cause organ failure. According to the MayoClinic, 1.5 percent of patients risk stroke when they have been exposed to the cardiopulmonary bypass machine.
Atrial Fibrillation
The heart has an electrical conduction system that causes it to contract. Surgery often causes trauma to this extremely sensitive pathway. Surgeons access the right coronary arteries by pulling the heart up from the chest and holding it upside down. This maneuver can easily damage the conduction system. Fifteen to 40 percent of bypass patients suffer atrial fibrillation after bypass. This rhythm results in chaotic contractions of the atrium and can be controlled with medication. Heart attacks occur in about 1% of patients due to arrhythmias.
References
- American Heart Association.org: Cardiovascular Disease Statistics
- MayoClinic.com: Coronary Artery Disease: Angioplasty or Bypass Surgery?
- BiomedCentral. Superficial and Deep Sternal Wound Infection after more than 9000 coronary artery bypass grafts, incidence, risk factors and mortality. Abbas Salehi Omran, MD and et.al. BMC Infectious Disease. 2007
- MerckManualOnline.com: Coronary Artery Bypass Grafting (CABG)
