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By:Sharmin Susiwala

INTRODUCTION:

Coronary artery bypass surgery, also coronary artery bypass graft (CABG, pronounced "cabbage") surgery, and colloquially heart bypass or bypass surgery is a surgical procedure performed to relieve angina and reduce the risk of death from coronary artery disease.

This surgery is usually performed with the heart stopped, necessitating the usage of cardiopulmonary bypass; techniques are available to perform CABG on a beating heart, so-called "off-pump" surgery.

INDICATIONS:

1.Disease of the left main coronary artery (LMCA).

2.Disease of all three coronary vessels (LAD, LCX and RCA).

3.Diffuse disease not amenable to treatment with a PCI.

4.High-risk patients such as those with severe ventricular dysfunction (i.e. low ejection fraction), or diabetes mellitus.

5.CABG is more effective than medical management at relieving symptoms, (e.g. angina, dyspnea, fatigue).

6.CABG is superior to PCI for some patients with multivessel CAD

PROCEDURE:1. The patient is brought to the operating room and moved on to

the operating table.

2. An anaesthetist places a variety of intravenous lines and injects a painkilling agent (usually fentanyl) followed within minutes by an induction agent (usually propofol) to render the patient unconscious.

3. An endotracheal tube is inserted and secured by the anaesthetist and mechanical ventilation is started. General anaesthesia is maintained by a continuous very slow injection of Propofol.

4. The chest is opened via a median sternotomy and the heart is examined by the surgeon.

5. The bypass grafts are harvested – frequent conduits are the internal thoracic arteries, radial arteries and saphenous veins. When harvesting is done, the patient is given heparin to prevent the blood from clotting.

6. In the case of "off-pump" surgery, the surgeon places devices to stabilize the heart.

7. If the case is "on-pump", the surgeon sutures cannulae into the heart and instructs the perfusionist to start cardiopulmonary bypass (CPB). Once CPB is established, the surgeon places the aortic cross-clamp across the aorta and instructs the perfusionist to deliver cardioplegia (a special potassium-mixture, cooled) to stop the heart and slow its metabolism. Usually the patient's machine-circulated blood is cooled to around 84 °F (29 °C)

8. One end of each graft is sewn on to the coronary arteries beyond the blockages and the other end is attached to the aorta.

9. The heart is restarted; or in "off-pump" surgery, the stabilizing devices are removed. In cases where the aorta is partially occluded by a C-shaped clamp, the heart is restarted and suturing of the grafts to the aorta is done in this partially occluded section of the aorta while the heart is beating.

10. Protamine is given to reverse the effects of heparin.

11. Chest tubes are placed in the mediastinal and pleural space to drain blood from around the heart and lungs.

12. The sternum is wired together and the incisions are sutured closed.

13. The patient is moved to the intensive care unit (ICU) to recover.

14. Nurses in the ICU focus on recovering the patient by monitoring blood pressure, urine output and respiratory status as the patient is monitored for bleeding through the chest tubes. If there is chest tube clogging, complications such as cardiac tamponade, pneumothorax or death can ensue. Thus nurses closely monitor the chest tubes and under take methods to prevent clogging so bleeding can be monitored and complications can be prevented.

15. After awakening and stabilizing in the ICU (approximately one day), the person is transferred to the cardiac surgery ward until ready to go home (approximately four days).

CONDUITS USED FOR BYPASS

The choice of conduits is highly dependent upon the particular surgeon and institution.

Typically,

1. Left internal thoracic artery (LITA) (previously referred to as left internal mammary artery or LIMA) is grafted to the left anterior descending artery and a combination of other arteries and veins is used for other coronary arteries.

2. Right internal thoracic artery (RITA),

3. Great saphenous vein from the leg

4. Radial artery from the forearm are frequently used

These vessels are usually harvested endoscopically, using a technique known as endoscopic vessel harvesting (EVH).

The right gastroepiploic artery from the stomach is infrequently used given the difficult mobilization from the abdomen.

POST-OPERATIVE PRECAUTIONS:

• Patients undergoing coronary artery bypass surgery will have to avoid certain things for eight to 12 weeks to reduce the risk of opening the incision. These are called sternal precautions.

• Patients need to avoid using their arms excessively, such as pushing themselves out of a chair or reaching back before sitting down.

• Patients are encouraged to build up momentum by rocking several times in their chair before standing up.

• Patients should avoid lifting anything in excess of 5–10 pounds.

• Patients should avoid overhead activities with their hands, such as reaching for sweaters from the top shelf of a closet or reaching for plates or cups from the cupboard.

COMPLICATIONS

People undergoing coronary artery bypass are at risk for the same complications as any surgery, plus some risks more common with or unique to CABG.

CABG associated

1. Postperfusion syndrome (pumphead)

2. Nonunion of the sternum; internal thoracic artery harvesting devascularizes the sternum increasing risk.

3. Myocardial infarction due to embolism, hypoperfusion, or graft failure.

4. Late graft stenosis, particularly of saphenous vein grafts due to atherosclerosis causing recurrent angina or myocardial infarction.

5. Acute renal failure due to embolism or hypoperfusion.

6. Stroke, secondary to embolism or hypoperfusion.

7. Vasoplegic syndrome, secondary to cardiopulmonary bypass and hypothermia

8. Grafts last 8 – 15 years, and then need to be replaced.

9. Pneumothorax

10. Hemothorax

11. Pericardial Tamponade

12. Pleural Effusion

General cardiac surgery

• Post-operative atrial fibrillation

General surgical

• Infection at incision sites or sepsis.

• Deep vein thrombosis (DVT)

• Anesthetic complications such as malignant hyperthermia.

• Keloid scarring

• Chronic pain at incision sites

• Chronic stress related illnesses

• Death