Coronary Artery Bypass Grafting


Cardiovascular disease is the leading cause of death in the United States. An American suffers from a myocardial infarction approximately every 40 seconds. On average, men are 65 years old and women are 72 years old at the time of the first myocardial infarction. The death rate for coronary artery disease (CAD) has decreased by 31.8% over the 10-year period from 2006 to 2016. This has been attributed to effective treatment and prevention, which includes coronary artery bypass grafting (CABG).

CABG is a surgical procedure to treat ischemic heart disease due to obstruction of the coronary arteries. The procedure involves redirecting blood flow around (or bypassing) an obstruction in a coronary artery using a vessel from an alternative location. Approximately 371,000 CABG procedures are performed annually in the United States.

How to Use It

The diagnosis of CAD is made using coronary angiography when a patient has a myocardial infarction or angina symptoms. Subsequently, most medical centers will employ a “heart team” approach in which the results of the angiography are discussed among the cardiologists and cardiothoracic surgeons. If a patient is deemed to be a CABG candidate, the patient will undergo the operation. CABG is performed with the intention to treat CAD that has already been diagnosed, and typically no further diagnostic evaluation is undertaken during the CABG procedure itself.

The choice to proceed with CABG versus percutaneous coronary intervention (PCI) is a clinical decision taking into account baseline patient characteristics, such as functional status along with the coronary anatomy (including the location and severity of the obstructing lesions), and the patient’s ability to tolerate and comply with the dual antiplatelet therapy required after PCI. In general, patients with diabetes mellitus and multivessel CAD undergo CABG. For patients with triple-vessel or complex CAD, the preferred treatment is also CABG. Patients who require dual antiplatelet agents for another indication or who are at high risk for surgery will typically undergo PCI. See Chapter 46: Percutaneous Coronary Intervention for more details about this procedure.

How It Is Done

CABG is performed by a cardiothoracic surgeon in the operating room. The main incision is the median sternotomy in which the anterior sternum is exposed. The surgeon will select a blood vessel to serve as the bypass blood vessel. The goal is to provide blood flow beyond the point of a blockage in a coronary artery. This is done by connecting a new blood vessel (the graft vessel), which comes with its own blood supply, to the distal part of the blocked coronary artery at a point past the blockage. In this manner, the blockage is bypassed and blood flow is restored to the coronary artery distal to the blockage.

The most common graft vessels are the left internal thoracic artery, the right internal thoracic artery, and the greater saphenous vein from the leg. The internal thoracic arteries typically remain connected to the subclavian artery proximally and are connected to the coronary artery distally. The greater saphenous vein is harvested from the leg and connected to the aorta proximally and to the diseased coronary artery distally. A radial artery may also be utilized, and it is harvested from the forearm and subsequently connected to the aorta proximally and the diseased coronary artery distally.

In order to perform a CABG operation, the heart must remain still, and the body must remain oxygenated and perfused. This is achieved using a cardiopulmonary bypass device in which blood is routed away from the heart and lungs to an external oxygenator and is returned to the aorta distal to the clamped proximal aorta. The heart is purposely stopped during this time (known as cardioplegia) to reduce myocardial oxygen demand and prevent myocardial damage. This is typically achieved using cold fluids, chemicals, or via electrical stimulation. Once the appropriate graft vessels have been harvested and connected to the target coronary arteries, the heart is disconnected from the cardiopulmonary bypass and normal circulation is restored. The patient is monitored for appropriate blood flow in the operating room, and subsequently the sternum is closed using wires and sutures. With a successful CABG, patients will experience a resolution of angina symptoms, and the overall risk of death and myocardial infarction is significantly reduced.

Medication Implications


  • Antiplatelet agents:

    • Aspirin 100–325 mg daily should be continued before CABG.

    • Any other additional antiplatelet agent needs to be discontinued prior to the procedure due to concern for bleeding. The guidelines discussed below provide recommendations for discontinuing dual antiplatelet agents prior to CABG; however, emergent or urgent cases may proceed with a minimum of 24 hours off the second agent based on the surgeon’s assessment of bleeding and the clinical urgency. These agents include:

      • Clopidogrel: Prodrug that becomes an active metabolite that is an irreversible inhibitor of the P2Y12 ADP receptor on platelets. The guidelines recommend discontinuing it 5 days prior to CABG. There are significant drug interactions that need to be considered. These include:

        • Omeprazole/esomeprazole: These two proton pump inhibitors inhibit the activity of clopidogrel due to inhibited cytochrome P450 2C19 activation and other cytochrome P450 2C19-inhibiting medications will have the same effect. Pantoprazole, lansoprazole, and dexlansoprazole have less of an impact on clopidogrel activity. The clinical relevance of these interactions is a controversial issue.

        • Opioids reduce the absorption of clopidogrel.

        • Selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and nonsteroidal anti-inflammatory drugs (NSAIDs) also inhibit platelet activity and may increase the risk of bleeding if used with clopidogrel.

        • Clopidogrel will increase the concentration of repaglinide and may lead to hypoglycemia if both medications are used in combination.

      • Prasugrel: Irreversible inhibitor of the P2Y12 ADP receptor on platelets. The guidelines recommend discontinuing it 7 days prior to CABG. A lower dose is indicated in individuals weighing less than 60 kg, and it is contraindicated in patients with a history of stroke or transient ischemic attack (TIA). It may be used with medications that inhibit or induce cytochrome P450. It can be used with glycoprotein IIb/IIIa inhibitors, statins, digoxin, proton pump inhibitors, and histamine-2 blockers and no significant drug interactions have been noted. Common nonbleeding-related adverse effects include hypertension, hyperlipidemia, shortness of breath, back pain, headache, nausea, dizziness, cough, hypotension, fatigue, and chest pain.

      • Ticagrelor: Reversible inhibitor of the P2Y12 ADP receptor on platelets. The guidelines recommend discontinuing it 5 days prior to CABG. A history of intracerebral hemorrhage is a contraindication, and there is a warning against use in severe hepatic impairment. The most common nonbleeding side effect is dyspnea, thought to be due to an increase in adenosine. Bradycardia and ventricular pauses have also been noted. There are significant drug interactions that need to be considered. These include:

        • Cytochrome P450 3A inhibitors (such as ketoconazole, clarithromycin, ritonavir) will lead to an increased concentration of ticagrelor.

        • Cytochrome P450 3A inducers (such as rifampin, phenytoin, carbamazepine, phenobarbital) will lead to a reduced concentration of ticagrelor.

        • Ticagrelor will increase the concentration of simvastatin and lovastatin.

        • Digoxin concentration can become increased due to p-glycoprotein inhibition and may need to be monitored.

        • Aspirin at doses greater than 100 mg daily can reduce the effectiveness of ticagrelor.

  • Oral anticoagulants should be discontinued prior to a CABG procedure. For warfarin, the international normalized ratio (INR) should be less than 2.0. Direct oral anticoagulants (such as dabigatran, apixaban, rivaroxaban, edoxaban) are generally discontinued 3 days prior to the surgery. Patients who require urgent CABG and cannot wait this period of time may be treated with reversal agents. Intravenous heparin may be continued as it will also be used during the procedure intraoperatively.

  • Beta blockers (such as metoprolol or carvedilol) should be started in all patients prior to CABG and continued afterward to reduce the risk of postoperative atrial fibrillation.


  • Anticoagulation: A continuous heparin infusion is maintained throughout the CABG procedure to prevent blood clotting within the cardiopulmonary bypass device.

  • Anesthetic agents and neuromuscular agents are utilized for general anesthesia and paralysis.

  • Cardioplegia solution is given to reduce myocardial oxygen demand. It is a mixture that includes calcium, magnesium, potassium, saline, and may be mixed with lidocaine or procainamide.

  • Blood pressure management: If the patient becomes hypotensive, the most common agent that is utilized is intravenous phenylephrine (alpha adrenergic agonist), which causes systemic vasoconstriction leading to an increase in blood pressure.

  • Cardiac arrhythmias may occur and a lidocaine bolus is typically given as prophylaxis during the procedure to prevent ventricular arrhythmias.


  • If aspirin 100–325 mg daily was not given preoperatively, it should be started within 6 hours postoperatively and continued indefinitely.

    • Clopidogrel 75 mg daily is a reasonable choice if the patient is intolerant to aspirin, despite not having evidence as strong as that for aspirin.

    • The current guidelines from 2011 do not recommend the routine use of dual antiplatelet agents post CABG; however, there are ongoing randomized controlled trials evaluating the use of a second agent either instead of aspirin or in addition to it. The current level of evidence is insufficient and has not led to an update of the guidelines. Dual antiplatelet agents are not routinely prescribed in all patients post CABG at this time. The decision to start or continue a second antiplatelet agent in certain patients, including when it should be started postoperatively, is an individualized decision that takes into account patient factors such as bleeding risk based on the operation and risk of graft vessel or native coronary artery stenosis based on the patient’s anatomy.

  • The most common cardiac event post CABG is the development of atrial fibrillation.

    • Beta blockers are utilized preoperatively and postoperatively to reduce the incidence of atrial fibrillation.

    • Anticoagulation for postoperative atrial fibrillation is typically instituted on day 3 after CABG to reduce the risk of bleeding in the first few days post procedure.

    • Choices for anticoagulation for atrial fibrillation include warfarin, dabigatran, rivaroxaban, apixaban, or edoxaban.

    • There are no randomized controlled trial data comparing direct oral anticoagulants with warfarin or head-to-head in the post-CABG patient. A retrospective study demonstrated an increased risk for pericardial or pleural effusions in patients who received a direct oral anticoagulant compared with warfarin. However, this data is limited, and the overall sample size was small. The choice of anticoagulation is an area that requires further research and prospective randomized controlled studies.

  • Beta blockers and statins should be prescribed to all patients upon discharge unless contraindicated. Angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers should be prescribed to all patients with a compelling indication (i.e., diabetes mellitus, heart failure with reduced ejection fraction, hypertension, chronic kidney disease) unless contraindicated.

  • Nonsteroidal anti-inflammatory cyclooxygenase-2 inhibitors should be avoided in the postoperative period, and they are specifically contraindicated in a “black box” warning due to increased risk of myocardial infarction and stroke. ,


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Nov 21, 2021 | Posted by in PHARMACY | Comments Off on Coronary Artery Bypass Grafting

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