Risk factors in Bypass Surgery - Why and How it is done

What is bypass surgery?

• This surgery is done to by-pass clogged arteries supplying blood to the heart. It creates a ‘bypass’ around the blocked part of a coronary artery to restore the blood supply to the heart muscle. 
• The surgery is called Coronary Artery Bypass Grafting, or CABG. Commonly known as bypass surgery.

Why is it done?

• Coronary arteries are blood vessels that supply the heart muscle with oxygen and nutrients. Fats and cholesterol can accumulate inside these arteries, and the arteries can gradually become clogged. (This buildup of fat and cholesterol plaque is called atherosclerosis). 
• When one or more of the coronary arteries becomes partially or totally blocked, the heart does not get an adequate blood supply. This is called ischaemic heart disease or coronary artery disease (CAD). It can cause heart pain (angina) or a heart attack (myocardial infarction). 
• The first symptom of CAD may be a heart attack (myocardial infarction).
• Coronary artery bypass surgery is one of the treatment options for ishcaemic heart disease (too little blood reaching the heart muscle). 
• Bypass surgery is indicated for disease of the left main coronary artery disease or multiple blockages in one or more arteries. It is also done for a failure of nonsurgical management. Nonsurgical management includes medication and/or angioplasty.

How is the surgery done?

• After the patient is anesthetised and becomes unconscious, the surgeon makes an incision in the middle of the chest and separates the breastbone. Through this incision, the surgeon can see the heart and aorta (the main blood vessel leading from the heart to the rest of the body). After surgery, the breastbone is rejoined with wires and the incision is closed.
• If a vein from the leg is to be used for the bypass, an incision is made in the leg and the saphenous vein removed by another surgeon operating simultaneously. This vein is located on the inside of the leg running from the ankle to the groin. It normally does only about 10% of the work of circulating blood from the leg back to the heart. Therefore, it can be taken out without harming the patient or adversely affecting the leg. It is common for the leg from which the vein is taken to swell slightly during recovery from the surgery, but this is only temporary and treated with elevation of the leg, and special stockings.
• Alternatively the internal mammary artery (IMA) can also be used for the graft. This has the advantage of staying open for many more years than the vein grafts, but there are some situations in which it cannot be used. Other arteries are also now being used in bypass surgery. The most common other artery used is the radial artery. This is one of the two arteries that supply the hand with blood. It can usually be removed from the arm without any impairment of blood supply to the hand.
• In the traditional surgery, the patient is connected to the heart-lung machine, or bypass pump, which adds oxygen to the blood and circulates blood to other parts of the body during the surgery. This is necessary because the heart muscle must be stopped before the graft can be done. One end of the graft is stitched to an opening below the blockage in the coronary artery. If the grafted vein is from the leg or the radial artery, its other end is stitched to an opening made in the aorta. If the grafted vessel is the mammary artery, its other end is already connected to the aorta.
• The entire surgery usually takes four to six hours. After the surgery, the patient is kept in the Intensive Care Unit. For a few days after the surgery, the patient is connected to monitors and tubes. Other techniques to do this surgery are used more and more frequently. One popular method is to avoid the use of the heart-lung machine. This is called off-pump coronary artery bypass or OPCAB. This operation allows the bypass to be created while the heart is still beating. The advantage being a quicker recovery and fewer complication especially in elderly patients and in patients with problem like kidney failure and previous brain strokes etc.

What are the risks of surgery?

• Heart attack can occur during 5% of these surgeries
• Stroke can also occur in 5% of these surgeries (the risk is greatest in those over 70 years old)
• Blood clots in legs and their migration to lungs.
• Death may occur in 1-2% of those who have the surgery (95-98% have no serious complications)
• Wound infection may occur in 1-4% of these surgeries. This complication is most often associated with obesity, diabetes, or a previous CABG.
• The incision in the chest or the graft site (if the graft was from the leg or arm) can be itchy, sore, numb, or bruised

The complications are affected by the following factors:

• Age - patients over 70 years old are at a slightly higher risk for complications
• Gender - women have a slightly higher risk
• Previous heart surgery puts a person at a higher risk
• Having another serious medical condition (such as diabetes, peripheral vascular disease, kidney disease, or lung disease) adds to the risk for complications.

What to expect after surgery?

• In the majority of people who have the surgery, the grafts remain open and functioning for 10 to 15 years. CABG improves blood flow to the heart but does not prevent the eventual recurrence of coronary blockage.
• Lifestyle changes are necessary - such as not smoking, improved diet, regular exercise, and treating high blood pressure and high cholesterol.
• After the operation, the patient spends 5-7 days in the hospital, with the first few days in an intensive-care unit (ICU). In the ICU, heart function is monitored continuously. Patients may require the temporary assistance of a breathing tube for a few hours after surgery. 
• Two to three tubes in the chest drain fluid from around the heart and are usually removed one to three days after surgery. 
• A urinary catheter in the bladder drains urine until the patient is able to void on his own. 
• When constant monitoring is no longer needed, usually within 12-24 hours, the patient is moved to a regular care unit. Activity is gradually resumed and the patient and the incision in the chest does not bother most people after the first 48-72 hours. After surgery, it takes 4-6 weeks to start feeling better.

During recovery it is normal to have:

• A poor appetite - it will take several weeks for it to return
• Swelling in the leg if the graft was taken from the leg
• Difficulty sleeping at night - this improves with time
• Constipation
• Mood swings and feel depressed - this will get better
• Difficulty with short-term memory or feel confused - this also improves with time.
• The full benefits from the operation may not be apparent until 3-6 months after surgery. Sexual activities may be resumed 4 weeks after surgery. All activities that do not cause fatigue are permitted, and the schedule for resuming normal activities is determined by the doctor.