Coronary Artery Bypass Grafting

Cardiac Surgeries: Coronary Artery Bypass Grafting (CABG)

CABG video

What is a CABG (Summary)?
A coronary artery bypass graft is a common cardiac surgery in patients with atherosclerosis in one or more of their coronary arteries. An artery or vein is harvested from a part of the body with collateral flow (sufficient perfusion despite the lack of a blood vessel), then, the heart is put on a bypass machine, redirecting blood from the IVC (inferior vena cava) and the SVC (superior vena cava) to be oxygenated and then resupplied to the all parts of the body except the heart. During bypass, the surgeon will attach these vessel grafts to the aorta (right and/or left aortic sinus) past the occlusion of the coronary artery.

CABG statistics

In the USA, around 170,000 Americans undergo CABG surgery with a 98% success rate. Common demographics for this procedure are adults between 60 and 70 years old. While utilization decreases with age, those 85 and older have the highest rate of decline. Males are most common candidates for this surgery.

Common risk factors that suggest a need for CABG include hypertension, diabetes, dyslipidemia, and prior myocardial infarction.

Common comorbidities are conditions like heart failure, angina, and left main coronary artery disease.

CABG vs PCI

CABG (Coronary Artery Bypass Grafting):

• Procedure: Involves surgically grafting a healthy blood vessel (usually from the patient's own body) to bypass a blocked coronary artery.

• Recovery: Requires a longer recovery period, typically several weeks to months, with a hospital stay of several days.

• Benefits: Grafting stays long term and minimizes risk for another MI.

• Risks: Higher risk of complications due to surgery, such as bleeding, infection, and stroke.

PCI (Percutaneous Coronary Intervention):

• Procedure: A catheter is inserted into a blood vessel, often in the wrist or groin, and guided to the blocked artery. A balloon is inflated to open the blockage, and a stent (a small mesh tube) is usually placed to keep the artery open.

• Recovery: Generally involves a shorter recovery time, with most patients able to return to normal activities within a few days to a couple of weeks.

• Benefits: Minimally invasive, quicker recovery, lower risk of surgical complications.

• Risks: May require repeat procedures to address restenosis (re-narrowing of the artery) or new blockages, and may not provide the same long-term benefits as CABG in all cases.

  • Does not work for blockage >70%.

CABG history and significance

History of CABG:

The first successful CABG surgery was performed in 1967 by Dr. René Favaloro at the Cleveland Clinic. He used the saphenous vein from the leg to bypass blocked coronary arteries.

• Early Evolution: In the early years, surgeons experimented with different graft materials and techniques to improve durability.

• Advances in the 1970s–1980s: Use of the left internal mammary artery (LIMA) became standard for bypassing the left anterior descending (LAD) artery due to superior long-term patency. Improved anesthesia, cardiopulmonary bypass machines, and postoperative care significantly increased survival rates.

• Off-Pump CABG (1990s): Surgeons developed the ability to perform bypasses on a beating heart without using a heart-lung machine, reducing some complications.

Significance of CABG

Gold Standard for Multi-Vessel Disease: CABG remains the best operation for patients with plaques in multiple coronary arteries, especially in hypertensive and diabetic patients.

Improved Survival & Quality of Life: It significantly reduces angina, improves exercise tolerance, and in many cases prolongs life expectancy.

Durable Results: Arterial grafts like the LIMA often remain open for 15–20+ years, offering better long-term outcomes than percutaneous coronary interventions (PCI) in certain groups.

Minimally Invasive CABG (Recent Advances)

Minimally Invasive Direct Coronary Artery Bypass (MIDCAB): Developed in the 1990s, this technique uses a small left chest incision (without sternotomy) to access the heart.

Hybrid Coronary Revascularization: Combines minimally invasive LIMA-to-LAD grafting with stenting of other blocked vessels in the same patient, often in a single hospital stay.

Benefits:

• Smaller incisions and less trauma

• Faster recovery and shorter hospital stay

• Reduced infection risk, especially in diabetic and obese patients

• Less postoperative pain and quicker return to normal activities

• Limitations: Best suited for certain lesions (especially LAD) and may not replace full sternotomy CABG in patients with extensive multi-vessel disease.

A minimally invasive CABG, however, is preferred for a single CABG by harvesting LIMA, complications can arise from multiple grafts.

When is CABG needed?

Major indications for a CABG include:

• Frequent MI, ST elevation, elevated troponin levels.

• Post MI CT scan angiography indicating severe multi-vessel coronary artery disease with 70% or higher blockage in 2 or more

• Reduced LVEF (Left ventricular ejection fraction), low left ventricle function, left ventricular dilation, trace mitral regurgitation or trace tricupsid regurgitation.

• Left main coronary disease with >50% blockage.

• PCI failure.

• Diabetes with multi-vessel disease (MVD)

Pre-operative care:

Patient assessment and lab workup:

• Detailed medical history, physical exam. Focus should be on cardiovascular health, comorbidities, and functional capacity. Normally, patients undergo a stress-echocardiogram.

  • Cardiac/CT angiogram, echocardiogram for heart function and blockage sites.

• Blood tests (CBC, kidney and liver function…)

• Chest X-ray

• EKG/ECG

Control of medical conditions:

• Look to control hypertension, diabetes, arrythmias.

• Stop smoking >4 weeks from surgery.

• Treatment of infections to boost immune health.

Medication Management:

• Continue Beta-Blockers and statins.

• Hold/ adjust:

  • ACE inhibitors 24 hours before operation (to control BP during procedure)

  • Anticoagulants (warfarin, DOACs): stop several days prior, bridge if necessary.

  • Antiplatelets ( aspirin often continued; clopidogrel/ticagrelor usually stopped 5–7 days before unless urgent)

Patient education and counseling:

• Explain risks associated with procedure

• Patient consent

• Discuss post-operative care for home and in hospital

Preoperative preparation:

• Anti-septic skin (shower before operation to minimize infection risk, hair clipping at and around surgical sites.

• NPO (fasting from midnight to surgery)

• Central line should be planned

• Prophylactic Antibiotics: Administer within 60 minutes before incision.

Surgical procedure :

Anesthesia & Patient Preparation

• General anesthesia with endotracheal intubation.

• Patient positioned supine; arms tucked unless radial artery harvest planned.

• Monitoring lines:

  • Arterial line (BP monitoring)
    Central venous or pulmonary artery catheter

  • Urinary catheter

  • Transesophageal echocardiography (TEE) probe: Comprehensive checkup for MR, TR, AR, LVEF, LV compliance…

• Skin prep from chin to mid-thigh (sternum and legs/forearms if graft harvest planned).

Median Sternotomy

• Midline skin incision from sternal notch to xiphoid.

• Sternum divided with oscillating saw.

• Sternal retractor inserted for exposure.

Graft Harvesting

Radial artery and Great Saphenous vein are harvested simultaneously by 2 PAs.

Left Internal Mammary Artery (LIMA)

• Accessed via median sternotomy bby cardiothoracic/ cardiac surgeon.

• The left pleural space is opened.

• LIMA dissected from the chest wall (pedicled or skeletonized technique).

• Branches clipped and divided.

• Distal end left attached until just before anastomosis to preserve flow.

Great Saphenous Vein (GSV)

• Leg elevated and prepped; incision along medial leg or endoscopic vein harvesting (EVH).
  Vein dissected free, side branches ligated or clipped.

• Vein flushed with heparinized saline to check for leaks, clipped at any openings.

• Stored in cold heparinized solution.

Radial Artery

• Pre-op Allen’s test or Doppler to confirm ulnar artery sufficiency and collateral flow.

• Incision along volar forearm.

• Flushed with vasodilator solution (e.g., papaverine, verapamil-nitroglycerin).

• Stored in vasodilator solution or heparinized solution until use.
  

Heparinization & Cannulation

• Heparin given to achieve ACT > 480 sec (normally 4-10,000 units)

• Aortic cannulation for arterial inflow.

• Right atrial (or bicaval) cannulation for venous drainage.

• Cardiopulmonary bypass (CPB) initiated by anesthesiologist
  

Myocardial Protection

• Aortic cross-clamp applied (Between aortic valve and emergence of coronary arteries to ensure cardioplegia does not enter systematic blood stream)

• Cold cardioplegia (high K+ solution) infused into coronary arteries to arrest the heart.

  • This is called antegrade

  • Cardioplegia is also often inserted into coronary sinus for the cardioplegia to reach some parts of the heart by veins where arteries cannot reach.

• Heart cooled with iced saline or cooling jacket to minimize oxygen consumption.

Distal Anastomoses (graft to coronary artery)

• Heart positioned to expose target vessels.

• Coronary artery opened distal to blockage.

• Distal end of graft (vein or radial artery) sewn end-to-side to coronary artery using 7-0 or 8-0 polypropylene suture.

• Sequential or individual anastomoses may be performed depending on targets.
  

Proximal Anastomoses (graft to aorta or LIMA to LAD)

• For vein or radial artery grafts:

  • After distal ends sewn, proximal ends attached to ascending aorta (end-to-side) with 6-0 polypropylene suture.

• For LIMA:

  • Remains attached to subclavian artery at its origin.

  • Distal end anastomosed directly to LAD artery.

Weaning from CPB

• Gradual rewarming of patient.

• Remove aortic cross-clamp; allow heart to resume beating; normally patient would need a pacemaker to get the heart to restore into sinus rhythm given it was arrested for a while.

• Check graft flow and cardiac function with TEE or flow probes.

• Slowly reduce CPB support while monitoring hemodynamics.
  

Hemostasis & Closure

• Heparin reversed with protamine until ACT reaches baseline established by perfusionist and anesthesiologist) (protamine clots while heparin does the opposite)

• Meticulous bleeding control.

• Placement of mediastinal and pleural chest tubes.

• Sternum closed with stainless steel wires.

• Subcutaneous tissue and skin closed in layers.
  

Postoperative Transfer

• Patient transported to cardiac ICU intubated for postoperative monitoring.
  
  

Post-operative care:

Immediate Post-Op (Cardiac ICU)

• Most patients remain intubated for 6–12 hours post-op.

• Extubation when stable: good oxygenation, hemodynamics, and neurological status.

• Continuous ECG, arterial BP, central venous pressure (CVP) or pulmonary artery catheter if needed.

• Maintain adequate preload, cardiac output, and blood pressure.

• Chest tube is inserted with SWAN catheter (thin, flexible tube inserted into the heart and pulmonary artery to monitor heart function and blood flow) placed.

Rhythm Management

• Watch for arrhythmias—atrial fibrillation is common (up to 40%).

• Treat with rate/rhythm control (beta-blockers, amiodarone).

Fluid & Electrolyte Balance

• Monitor urine output (>0.5 mL/kg/hr).

• Correct potassium, magnesium, and calcium to reduce arrhythmia risk.

Bleeding & Coagulation

• Monitor chest tube output—>150 mL/hr may require surgical review.

• Transfuse blood products as needed.

Pain Control & Early Mobilization

• IV opioids initially → transition to oral analgesics (morphine is common)

• Adequate pain control facilitates deep breathing and coughing (reduces pneumonia risk).

• Begin physiotherapy and mobilization within 24–48 hours if stable.
  

Respiratory Care

• Incentive spirometry every 1–2 hours while awake.

• Early ambulation to prevent atelectasis and DVT.
  

Infection Prevention

• Maintain strict sternal wound care (dressing change every few hours)

• Monitor for redness, swelling, drainage.

• Continue perioperative antibiotics for 24–48 hours only (prolonged use not recommended).
  

Medication Management

• Antiplatelets: Aspirin daily; dual antiplatelet therapy if indicated.
  Beta-blockers: To reduce arrhythmia risk and improve survival.

• Statins: For secondary prevention of atherosclerosis.

• ACE inhibitors/ARBs: If LV dysfunction, diabetes, or hypertension.

Medications are given as they were, with dosages reestablished.

Discharge Planning & Long-Term Care

• Cardiac Rehabilitation: Structured program of exercise, diet, and lifestyle education.

• Risk Factor Modification: Stop smoking, control BP, lipids, and diabetes.

• Follow-Up: Wound check in 1–2 weeks; cardiology follow-up for ongoing care.