CABG essay .. how the procedure is done ... what are all the instruments are used
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CABG coronary artery bypass grafting procedure steps instruments used surgical technique
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I now have comprehensive material from Harrison's Principles, Miller's Anesthesia, Sabiston's Surgery, J&J MedTech operative steps, and AORN instrumentation guide. I have enough to write a thorough, well-structured essay. Let me compile it now.
Coronary Artery Bypass Grafting (CABG): A Comprehensive Essay
1. Introduction
Coronary artery bypass grafting (CABG) is one of the most widely performed cardiac surgical procedures in the world, performed approximately half a million times per year in the United States alone, with an overall success rate near 98%. It is the standard surgical treatment for obstructive coronary artery disease (CAD), particularly when medical therapy or percutaneous coronary intervention (PCI) is not suitable. The procedure creates new routes for blood to reach the myocardium by bypassing blocked coronary arteries using vascular conduits harvested from elsewhere in the patient's body.
CABG is preferred over PCI in patients with:
-
Significant left main coronary artery stenosis
-
Three-vessel CAD, especially with LV dysfunction (EF <35%)
-
Diabetes mellitus with multivessel disease
-
Complex multivessel disease (high SYNTAX score)
-
Harrison's Principles of Internal Medicine, 22E, p. 2104
2. Indications
| Indication | Class |
|---|---|
| Multivessel CAD + LVEF ≤35% | COR 1 |
| Left main CAD (significant stenosis) | COR 1 |
| Diabetes + multivessel CAD | COR 1 |
| Multivessel CAD, LVEF 35-50% | COR 2a |
| Complex three-vessel disease | COR 2a |
- Sabiston Textbook of Surgery, p. 2496
3. Preoperative Preparation
Before the procedure:
- Anesthesia: A radial arterial line and Swan-Ganz catheter (in the external jugular vein) are inserted for hemodynamic monitoring. ECG leads are placed.
- Catheterization: A Foley catheter is placed for urinary output monitoring.
- Positioning: The patient is positioned supine with legs "frogged" (externally rotated and supported) to allow leg access for saphenous vein harvesting. Arms are tucked to the sides.
- Skin prep: A Hibiclens scrub is performed followed by ChloraPrep or DuraPrep antiseptic solution. Sterile towels are placed between the legs and Ioban adhesive drapes are applied.
- Monitoring: Five-lead ECG, invasive arterial pressure catheter, and transesophageal echocardiography (TEE) are standard. Pulmonary artery pressure (PAP) and cardiac output (CO) monitoring may also be used.
4. Surgical Procedure - Step by Step
Step 1: Median Sternotomy (Access)
The patient is placed supine. A skin incision is made in the midline from the jugular notch to the xyphoid process. Using electrocautery (Bovie), dissection proceeds along the bone. Blunt finger dissection confirms that the retrosternal space is clear at both the upper manubrium and the xyphoid.
A sternal saw (battery-operated oscillating saw) is used to divide the sternum along its entire length in the midline. Bleeding from the sternal marrow and periosteum is controlled with bone wax or a topical absorbable hemostat (e.g., SURGICEL FIBRILLAR). A sternal retractor (e.g., Favaloro retractor) is then placed to separate and hold the two halves of the sternum apart, exposing the mediastinum and pericardium.
Step 2: Conduit Harvesting
While one surgical team opens the chest, a second team simultaneously harvests the conduits:
a) Left Internal Mammary Artery (LIMA)
The LIMA is the most important conduit for CABG. It is mobilized from the inner chest wall using electrocautery, with care taken to preserve its pedicle. It is harvested as a pedicled graft (the distal end is cut and the proximal origin on the subclavian artery remains intact). The LIMA-to-LAD anastomosis provides superior long-term patency compared to saphenous vein grafts.
b) Greater Saphenous Vein (GSV)
A vein is harvested from the leg through a skin incision along the medial thigh and calf. Endoscopic techniques now allow harvesting through small port incisions with minimal scarring. Side branches are ligated. The vein must be handled gently to avoid endothelial damage.
c) Radial Artery
Harvested from the non-dominant forearm using an electrocautery or advanced energy device. It is more durable than saphenous vein grafts and associated with better long-term survival. A modified Allen's test is performed preoperatively to confirm adequate ulnar artery collateral flow.
d) Right Internal Mammary Artery (RIMA)
May be harvested if bilateral mammary artery grafting is indicated, especially in younger patients.
- Harrison's Principles, p. 2104; Miller's Anesthesia, p. 7596
Step 3: Pericardiotomy and Heart Exposure
The pericardium is opened longitudinally from the diaphragm upward to its reflection on the upper ascending aorta. The cut edges of the pericardium are suspended with sutures to create a "pericardial cradle" that lifts and stabilizes the heart and provides optimal exposure.
Step 4: Systemic Anticoagulation
Heparin is administered intravenously (typically 300-400 units/kg) to achieve full anticoagulation before cannulation. Activated clotting time (ACT) is checked and maintained >400-480 seconds throughout the bypass period.
Step 5: Cardiopulmonary Bypass (CPB) Cannulation
For on-pump CABG:
- Aortic cannula is inserted into the ascending aorta (after a purse-string suture and Rumel tourniquet) to deliver oxygenated blood from the heart-lung machine back to the systemic circulation.
- Venous cannulas are inserted into the right atrium (two-stage cannula) or into both venae cavae individually, to drain deoxygenated blood to the bypass circuit.
- The CPB circuit includes a roller pump or centrifugal pump, an oxygenator, a heat exchanger, and arterial filters.
- A cell-saver suction device retrieves blood lost during the procedure for auto-transfusion.
Step 6: Aortic Cross-Clamping and Cardioplegic Arrest
A cross-clamp is placed across the ascending aorta distal to the aortic cannula. This isolates the coronary circulation. Cardioplegia solution (cold crystalloid or blood-based, potassium-rich) is infused into the aortic root (antegrade) or into the coronary sinus (retrograde) to arrest the heart in diastole and protect the myocardium from ischemia. The heart is also cooled with topical ice slush (myocardial hypothermia).
The operating field is now still and bloodless, allowing precise anastomosis.
Step 7: Distal Anastomoses
Using magnification loupes (x2.5-4.5), the surgeon identifies the target coronary artery (e.g., LAD, RCA, circumflex). An arteriotomy (longitudinal incision) is made in the coronary artery distal to the blockage, typically 5-7 mm in length, using a coronary knife and Potts scissors.
The conduit is trimmed to the appropriate length and fashioned in a "heel-and-toe" configuration. The distal anastomosis is sewn using a continuous 7-0 or 8-0 polypropylene (Prolene) suture under optical magnification. Coronary dilators may be used to verify graft patency before completing the anastomosis.
Each target vessel gets its own distal anastomosis (e.g., LIMA to LAD, saphenous vein to obtuse marginal, saphenous vein to RCA).
Step 8: Proximal Anastomoses (Aortic End)
For free grafts (saphenous vein or free radial artery):
- A side-biting (partial occlusion) clamp is applied to the ascending aorta.
- A circular aortic punch creates an aortotomy.
- The proximal end of the conduit is sewn to the aorta in an end-to-side fashion with a 5-0 or 6-0 polypropylene suture.
Alternatively, the proximal end of a free conduit can be anastomosed to the LIMA as a "T-graft" or "Y-graft," avoiding the need for aortic manipulation (useful in heavily calcified "porcelain" aortas).
The LIMA does not require a proximal anastomosis as it remains attached to its origin on the subclavian artery.
Step 9: Weaning from CPB and De-airing
The aortic cross-clamp is removed. The heart is allowed to reperfuse. The heart usually resumes beating spontaneously; DC cardioversion may be needed if ventricular fibrillation occurs.
De-airing maneuvers are performed: the patient is placed in Trendelenburg (head-down) position, and the heart is vented and filled to expel any residual air.
The patient is slowly weaned from cardiopulmonary bypass as cardiac function is confirmed (by TEE and hemodynamic monitoring). Inotropic support (dopamine, dobutamine, or milrinone) may be administered if needed.
Step 10: Protamine Reversal
Protamine sulfate is given to reverse heparin anticoagulation. ACT returns to baseline.
Step 11: Chest Closure
Temporary epicardial pacing wires (atrial and ventricular) are placed for postoperative pacing if needed. Mediastinal and pleural drainage tubes are inserted. The sternum is closed with stainless steel wires (typically 6-8 wires) using a figure-of-eight or simple wire technique. Wire instruments (wire needle holders, wire twisters, wire cutters) are used. The subcutaneous tissue and skin are closed in layers.
5. Off-Pump CABG (OPCAB)
In OPCAB, the heart is not arrested and CPB is not used. Instead:
- A mechanical stabilizer (e.g., ACROBAT retractor with suction-based footplates) immobilizes the target vessel area while the rest of the heart continues to beat.
- A blower/mister (e.g., AXIUS device) delivers CO2-enriched sterile saline aerosol to keep the anastomotic site clear of blood.
- Retractor tapes (elastic loops) encircle the coronary artery to minimize bleeding during the arteriotomy.
- Intracoronary shunts (FloCoil) maintain coronary perfusion during anastomosis.
- The proximal anastomosis is made using a partial occlusion clamp on the aorta.
OPCAB reduces some risks (blood product use, inflammatory response) but has not been shown to significantly reduce neurocognitive complications.
- Miller's Anesthesia, 10e, p. 7595-7596
6. Instruments Used in CABG
Access and Exposure Instruments
| Instrument | Purpose |
|---|---|
| Sternal saw (oscillating, battery-operated) | Divides the sternum for median sternotomy |
| Favaloro/Sternal retractor | Retracts and holds the sternal edges apart throughout the procedure |
| Rultract retractor | Alternative sternal retractor providing wide chest opening |
| Electrocautery (Bovie) | Hemostasis along skin and soft tissue dissection |
| Bone wax | Seals bleeding from sternal bone marrow edges |
| SURGICEL Fibrillar | Absorbable topical hemostat for sternal marrow edges |
Cannulation and Bypass Instruments
| Instrument | Purpose |
|---|---|
| Aortic cannula | Delivers oxygenated blood from heart-lung machine to aorta |
| Venous cannula (two-stage or bicaval) | Drains venous blood into bypass circuit |
| Aortic cross-clamp | Occludes aorta to allow cardioplegia |
| Side-biting (Satinsky) clamp | Partial occlusion of aorta for proximal anastomosis |
| Cardioplegia delivery set | Delivers potassium-rich arrest solution (antegrade/retrograde) |
| Rumel tourniquet/passer | Tightens purse-string sutures at cannulation sites |
| Cardiopulmonary bypass (CPB) circuit | Heart-lung machine: roller/centrifugal pump, oxygenator, heat exchanger |
| Cell-saver | Autotransfusion device collecting shed blood |
Coronary and Anastomosis Instruments
| Instrument | Purpose |
|---|---|
| Coronary knife / #15 blade | Initial arteriotomy incision on coronary artery |
| Potts-Smith scissors (angled, 45°/60°) | Extends and trims arteriotomy; cutting coronary vessel |
| Jacobson micro scissors (45°, 90°, 125° angulations) | Precise cutting of delicate coronary vessels; Ball-tip versions secure arteriotomy opening |
| DeBakey atraumatic forceps | Grasping conduit and tissues without crushing |
| Tying micro tissue forceps (Resano, Micro-tip) | Handling fine sutures near anastomosis site |
| Coronary dilators | Verify lumen patency and calibrate conduit opening |
| Vascular hook (Carpentier, 90°) | Retracts and exposes coronary vessel for anastomosis |
| Natali's spatula | Dual-purpose retraction and dissection instrument |
| Coronary needle holders (micro, angled) | Drive 7-0 and 8-0 needles for anastomotic sutures |
| Bulldog clamps + applier/remover | Temporarily occlude vessels; identify proximal vs. distal direction |
| Aortic punch | Creates circular aortotomy for proximal anastomosis |
Off-Pump Specific Instruments
| Instrument | Purpose |
|---|---|
| ACROBAT / Octopus stabilizer | Suction-based device to immobilize target vessel area on beating heart |
| XPOSE device | Cardiac positioning device to expose posterior coronary targets |
| AXIUS Blower/Mister | Delivers CO2 + saline mist to keep field clear of blood during anastomosis |
| Elastic retractor tapes (silastic loops) | Occludes the coronary vessel around the anastomosis site |
| FloCoil intracoronary shunts | Maintains coronary blood flow distal during anastomosis |
| Dubost / Couëtil retractors | Specialized retractors for coronary surgery exposure |
Closure Instruments
| Instrument | Purpose |
|---|---|
| Stainless steel wires | Reapproximate and close the divided sternum |
| Wire needle holders | Drive the heavy wires through the sternal bone |
| Wire twister | Twist and tighten the wires to close the sternum |
| Wire cutter | Trim excess wire length after closure |
| Epicardial pacing wires | Temporary postoperative pacing leads |
| Chest drains (mediastinal/pleural tubes) | Postoperative fluid/blood drainage |
7. Conduit Selection Summary
| Conduit | Patency at 10 years | Notes |
|---|---|---|
| LIMA (pedicled, to LAD) | >90% | Gold standard; improves survival |
| RIMA | >85% | Bilateral IMA improves outcomes in younger patients |
| Radial artery | 80-85% | Better than SVG; requires Allen's test preop |
| Saphenous vein graft | 50-60% | Most available; occlusion rate ~2%/year after year 1 |
- Harrison's Principles, 22E, p. 2104
8. Postoperative Care
- Patient is transferred to cardiac ICU, typically intubated.
- Hemodynamic monitoring continues (arterial line, central venous pressure, PA catheter in selected cases).
- Chest drains are monitored for bleeding; drainage >200 mL/hour warrants re-exploration.
- Temporary pacing may be needed for bradycardia or heart block.
- Aspirin is resumed within 6 hours postoperatively to maintain graft patency.
- Statin therapy reduces graft failure and improves survival.
- Average hospital stay is 5-7 days; return to full activity in 6-8 weeks.
9. Complications
| Complication | Mechanism |
|---|---|
| Perioperative MI (Type 5 MI) | Cardiac troponin rise >99th percentile within 48 hours of CABG |
| Stroke | Aortic manipulation, air/debris embolism, atrial fibrillation |
| Atrial fibrillation | Occurs in 20-40% postop; usually self-limiting |
| Wound infection / sternal dehiscence | Especially in diabetics; bilateral IMA increases risk |
| Renal failure | Low perfusion during CPB; contrast nephropathy if recent angiography |
| Cognitive dysfunction | Microemboli from CPB circuit |
| Graft failure | Early thrombosis or late atherosclerosis of SVG |
- Sabiston Textbook of Surgery, p. 2486; Harrison's Principles, 22E, p. 2104
Summary
CABG remains the most studied cardiac operation in history. Its success depends on meticulous surgical technique, appropriate conduit selection (LIMA-to-LAD is mandatory when possible), adequate myocardial protection during CPB, and careful postoperative management. The modern CABG armamentarium ranges from the simple sternal saw and Bovie to highly specialized micro-instruments, suction stabilizers, and automated cell-salvage systems - all working together to give the coronary circulation a new, durable pathway around obstructed vessels.
Sources:
- Harrison's Principles of Internal Medicine, 22E - Coronary Artery Bypass Grafting section
- Miller's Anesthesia, 10e - Off-Pump Coronary Artery Bypass (Vol. 2)
- Sabiston Textbook of Surgery - Coronary Artery Disease and Revascularization
- AORN - Cardiothoracic Instrumentation Guide
- J&J MedTech Surgical Education - CABG Operative Steps
- AST - Off-Pump CABG Surgical Technologist Guide
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