Coronary artery bypass surgery

Terminology

Number of arteries bypassed

Efficacy

• The 2004 ACC/AHA CABG guidelines state CABG is the preferred treatment for:
• * Disease of the left main coronary artery.
• * Disease of all three coronary arteries.
• * Diffuse disease not amenable to treatment with a PCI.
• The 2005 ACC/AHA guidelines further state that CABG is the preferred treatment with other high-risk patients such as those with severe ventricular dysfunction, or diabetes mellitus.
• Bypass surgery can provide relief of angina when the location of partial obstructions precludes improving blood flow with stents.
• There is no survival benefit with bypass surgery vs. medical therapy in stable angina patients.
• Bypass surgery does not prevent future myocardial infarctions.

Results compared to stent placement

• Both PCI and CABG are more effective than medical management at relieving symptoms,.
• CABG is superior to PCI for some patients with multivessel CAD
• The Surgery or Stent trial was a randomized controlled trial that compared CABG to PCI with bare-metal stents. The SoS trial demonstrated CABG is superior to PCI in multivessel coronary disease.
• The SYNTAX trial was a randomized controlled trial of 1800 patients with multivessel coronary disease, comparing CABG versus PCI using drug-eluting stents. The study found that rates of major adverse cardiac or cerebrovascular events at 12 months were significantly higher in the DES group. This was primarily driven by higher need for repeat revascularization procedures in the PCI group with no difference in repeat infarctions or survival. Higher rates of strokes were seen in the CABG group.
• The FREEDOM trial will compare CABG and DES in patients with diabetes. The registries of the nonrandomized patients screened for these trials may provide as much robust data regarding revascularization outcomes as the randomized analysis.
• A study comparing the outcomes of all patients in New York state treated with CABG or percutaneous coronary intervention demonstrated CABG was superior to PCI with DES in multivessel coronary artery disease. Patients treated with CABG had lower rates of death and of death or myocardial infarction than treatment with a coronary stent. Patients undergoing CABG also had lower rates of repeat revascularization. The New York State registry included all patients undergoing revascularization for coronary artery disease, but was not a randomized trial, and so may have reflected other factors besides the method of coronary revascularization.
• A meta-analysis with over 6000 patients showed that coronary artery bypass was associated with lower risk for major adverse cardiac events compared to drug-eluting stenting. However, patients had a higher risk of stroke events.

Complications

CABG associated

• Postperfusion syndrome, a transient neurocognitive impairment associated with cardiopulmonary bypass. Some research shows the incidence is initially decreased by off-pump coronary artery bypass, but with no difference beyond three months after surgery. A neurocognitive decline over time has been demonstrated in people with coronary artery disease regardless of treatment. However, a 2009 research study suggests that longer term cognitive decline is not caused by CABG but is rather a consequence of vascular disease. Loss of mental function is a complication of bypass surgery in elderly people, and might influence procedure cost benefit considerations. Several factors may contribute to immediate cognitive decline. The heart-lung blood circulation system and the surgery itself release a variety of debris, including bits of blood cells, tubing, and plaques. For example, when surgeons clamp and connect the aorta to tubing, resulting emboli block blood flow and cause mini strokes. Other heart surgery factors related to mental damage may be events of hypoxia, high or low body temperature, abnormal blood pressure, irregular heart rhythms, and fever after surgery.
• Nonunion of the sternum; internal thoracic artery harvesting increases the sternum devascularization risk.
• Myocardial infarction due to embolism, hypoperfusion, or graft failure. While remote ischaemic preconditioning reduces the cardiac troponin T release measured at 72 hours after surgery and cardiac troponin I release measured at 48 hours and 72 hours after surgery, it does not reduce reperfusion injury in people undergoing cardiac surgery.
• Late graft stenosis, particularly of saphenous vein grafts due to atherosclerosis causing recurrent angina or myocardial infarction.
• Acute renal failure due to embolism or hypoperfusion.
• Stroke, secondary to embolism or hypoperfusion.
• Vasoplegic syndrome, secondary to cardiopulmonary bypass and hypothermia
• Graft failure: grafts last 8–15 years, and then need to be replaced.
• Pneumothorax: An air collection around the lung that compresses the lung
• Hemothorax: Blood in the space around the lungs
• Pericardial tamponade: Blood collection around the heart that compresses the heart and causes poor body and brain perfusion. Chest tubes are placed around the heart and lung to prevent this. If the chest tubes become clogged in the early post operative period when bleeding is ongoing this can lead to pericardial tamponade, pneumothorax or hemothorax.
• Pleural effusion: Fluid in the space around the lungs. This can lead to hypoxia which can slow recovery.
• Pericarditis
• Lower extremity edema, extravasation, inflammation, and eccymoses from vein harvest; entrapment of up to of fluid in the extremity is common. This is managed with a thigh length compression stocking, elevation of the limb, and early and frequent slow walking; as well as avoidance of standing in place, sitting, and bending the leg at the knee more than a few degrees.

  Open heart surgery associated

• Post-operative atrial fibrillation and atrial flutter.
• Anemia - secondary to blood loss, plus the anemia of inflammation, inflammation being inevitable with opening the chest plus harvesting of leg vein for grafting. A fall in the hemoglobin from normal preoperative levels to postoperative levels of 6 to 10 are inevitable. There is no benefit from transfusions until the hemoglobin falls below 7.5. Institutions should establish protocols to ensure transfusions are not given unless the hemoglobin falls below 7.5 without some additional compelling reason.
• Delayed healing or refracture of sternum - the sternum is bifurcated logitudinally and retracted to access the heart. Failure to follow "sternal precautions" following surgery could result in delayed healing or refracture of the sternum which was sutured at the closure of the chest wound:
• *Hold a pillow against the chest whenever getting out of or into a chair or bed; or coughing, sneezing, blowing nose, or laughing, in order to oppose the intrathoracic outward force created by these activities on the healing sternum.
• *Avoid using the pectoral muscles, such as by pushing on the chair arms to assist one's self out of a chair, or by using the arms to assist in sitting down. Proper standing technique is to rock three times in the chair and then stand to provide momentum for moving the center of gravity from the sitting to the standing position. Proper sitting technique is to slowly lower the bottom toward the chair seat using gluteus and quadriceps muscles without grabbing the chair arms. Second, patients should avoid lifting objects utilizing the pectoral muscles: carrying light objects with arms extended down at sides, and lifting light objects with the elbows pressed to the chest and using the biceps, are acceptable. Also, avoid using the arms overhead.
• *Avoid sitting in the car front seat for at least four weeks: the explosion of the deployment of an airbag could refracture the sternal union.

  General surgery associated

• Infection at incision sites
• Sepsis
• Deep vein thrombosis
• Anesthetic complications such as malignant hyperthermia
• Keloid scarring
• Chronic pain at incision sites
• Chronic stress related illnesses

  Procedure

1. The patient is brought to the operating room and moved onto the operating table.
2. An anaesthetist or anesthesiologist places intravenous and arterial lines and injects an analgesic, usually fentanyl, intravenously, followed within minutes by an induction agent 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 with an inhaled volatile anesthetic agent such as isoflurane.
4. The chest is opened via a median sternotomy and the heart is examined by the surgeon.
5. The bypass grafts are harvested – frequent vessels are the internal thoracic arteries, radial arteries and saphenous veins. When harvesting is done, the patient is given heparin to inhibit blood clotting.
6. In the case of "off-pump" surgery, the surgeon places devices to stabilize the heart.
7. In the case of "on-pump" surgery, the surgeon sutures cannulae into the heart and instructs the perfusionist to start cardiopulmonary bypass normally instructing the perfusionist to "Go on pump". Once CPB is established, there are two technical approaches: either the surgeon places the aortic cross-clamp across the aorta and instructs the perfusionist to deliver cardioplegia with a cooled potassium mixture to stop the heart and slow its metabolism or performing bypasses on beating state.
8. One end of each vein graft is sewn on to the coronary arteries beyond the obstruction and the other end is attached to the aorta or one of its branches. For the internal thoracic artery, the artery is severed and the proximal intact artery is sewn to the LAD beyond the obstruction. Aside the latter classical approach, there are emerging techniques for construction of composite grafts as to avoiding connecting grafts on the ascending aorta in view of decreasing neurologic complications.
9. The heart is restarted by removing the aortic cross clamp; 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. Once the grafts are completed distally and proximally, the patient is rewarmed to a normal temperature and the heart and other pressures are normal to support coming off the bypass machine, weaning off the bypass machine begins.
11. The perfusionist makes sure they have enough volume to come off bypass, confirms that anesthesia is ventilating the patient, confirms that vacuum assist is off, and vocalizes each step in the weaning process to the surgeon and anesthesia. Volume can be given to the patient through the arterial line of the bypass machine while the aortic cannula is still in.
12. Protamine is given to reverse the effects of heparin.
13. Chest tubes are placed in the mediastinal and pleural space to drain blood from around the heart and lungs.
14. The sternum is wired together and the incisions are sutured closed.
15. The patient is moved to an intensive care unit or cardiac universal bed to recover. Nurses in the ICU monitor blood pressure, urine output, respiratory status, and chest tubes for excessive or no drainage.
16. After awakening and stabilizing in the ICU for 18 to 24 hours, the person is transferred to the cardiac surgery ward. If the patient is in a CUB, equipment and nursing is "stepped down" appropriate to the patient's progress without having to move the patient. Vital sign monitoring, remote rhythm monitoring, early ambulation with assistance, breathing exercises, pain control, blood sugar monitoring with intravenous insulin administration by protocol, and anti-platelet agents are all standards of care.
17. The patient without complications is discharged in four or five days.

    Minimally invasive technique

Choice of source of grafts

Follow up

• Acute - patients without complications are typically seen 3–4 weeks post operatively, at which time driving may be resumed and formal cardiac rehabilitation begun to increase aerobic endurance and muscular strength.
• Chronic -
• *a cardiac stress test at five years is recommended, even in the absence of cardiac symptoms.
• *an intensive medical regimen including statins, aspirin, and aerobic exercise is essential to delaying the progression of plaque formation in both the native and grafted vessels.

  Number performed

History

• The first coronary artery bypass surgery was performed in the United States on May 2, 1960, at the Albert Einstein College of Medicine-Bronx Municipal Hospital Center by a team led by Robert H. Goetz and the thoracic surgeon, Michael Rohman with the assistance of Jordan Haller and Ronald Dee. In this technique the vessels are held together with circumferential ligatures over an inserted metal ring. The internal mammary artery was used as the donor vessel and was anastomosed to the right coronary artery. The actual anastomosis with the Rosenbach ring took fifteen seconds and did not require cardiopulmonary bypass. The disadvantage of using the internal mammary artery was that, at autopsy nine months later, the anastomosis was open, but an atheromatous plaque had occluded the origin of the internal mammary that was used for the bypass.
• Soviet cardiac surgeon, Vasilii Kolesov, performed the first successful internal mammary artery–coronary artery anastomosis in 1964. However, Goetz has been cited by others, including Kolesov, as the first successful human coronary artery bypass. Goetz's case has frequently been overlooked. Confusion has persisted for over 40 years and seems to be due to the absence of a full report and to misunderstanding about the type of anastomosis that was created. The anastomosis was intima-to-intima, with the vessels held together with circumferential ligatures over a specially designed metal ring. Kolesov did the first successful coronary bypass using a standard suture technique in 1964, and over the next five years he performed 33 sutured and mechanically stapled anastomoses in Leningrad, USSR.
• René Favaloro, an Argentine surgeon, achieved a physiologic approach in the surgical management of coronary artery disease—the bypass grafting procedure—at the Cleveland Clinic in May 1967. His new technique used a saphenous vein autograft to replace a stenotic segment of the right coronary artery. Later, he successfully used the saphenous vein as a bypassing channel, which has become the typical bypass graft technique we know today; in the U.S., this vessel is typically harvested endoscopically, using a technique known as endoscopic vessel harvesting.
• Soon Dudley Johnson extended the bypass to include left coronary arterial systems.
• In 1968, doctors Charles Bailey, Teruo Hirose and George Green used the internal mammary artery instead of the saphenous vein for the grafting.

  Cost