Part 1: Redo Median Sternotomy (Redo Open-Heart Surgery)
Redo median sternotomy is a highly challenging and major surgical procedure. It refers to re-entering the chest cavity and mediastinum by reopening the sternum (median sternotomy) in a patient who has previously undergone open-heart surgery (e.g., coronary artery bypass grafting – CABG, valve replacement/repair, congenital heart disease correction, aortic surgery, etc.).
Here are key points to understand about redo sternotomy:
Core Challenges and Risks:
1. Tissue Adhesions:This is the greatest challenge. After the first surgery, dense scar tissue adhesions form between the heart, great vessels, lung tissue, etc., and the posterior sternal wall, as well as between these structures themselves. Dissecting these adhesions is extremely time-consuming, difficult, and highly prone to causing:
* Massive Bleeding: Injury to the heart, great vessels (aorta, vena cava, etc.), or grafted vessels (e.g., bypass grafts).
* Tissue Damage: Injury to lung tissue, the phrenic nerve (causing diaphragmatic paralysis), recurrent laryngeal nerve (causing hoarseness), etc.
2. Altered Anatomy: The initial surgery may have altered normal anatomical relationships (e.g., position of grafted vessels), increasing the difficulty of identifying structures and performing the operation.
3. Fragile Sternum: The sternum may have healed incompletely after the first surgery or have retained fixation wires, increasing the risk during resternotomy, potentially leading to sternal fracture or poor healing (sternal dehiscence).
4. Patient Condition: Patients undergoing redo surgery are often older, have more severe underlying conditions (e.g., coronary artery disease, heart failure, lung disease, renal insufficiency, diabetes), and have reduced overall tolerance.
5. Prolonged Surgery Time: Due to the difficulty of dealing with adhesions, surgery time is typically much longer than the initial operation.
6. Significantly Increased Complication Risk:
* Perioperative Mortality: Significantly higher than primary sternotomy.
* Massive Bleeding and Transfusion Needs: Very high risk.
* Low Cardiac Output Syndrome: Severely compromised heart pumping function.
* Respiratory Failure: Requiring prolonged mechanical ventilation.
* Renal Failure.
* Stroke.
* Wound Infection and Mediastinitis: Increased risk.
* Prolonged Recovery: Longer hospital stay, slower rehabilitation.
Why is Redo Sternotomy Needed? Common Reasons Include:
1. Valve-Related:
* Bioprosthetic valve degeneration (re-replacement).
* Mechanical valve failure or paravalvular leak.
* Previous valve repair failure requiring re-repair or replacement.
2. Post-Coronary Artery Bypass Grafting (CABG):
* Graft occlusion or stenosis (especially venous grafts).
* Progression of native coronary artery disease.
* Need for redo CABG or hybrid procedures.
3. Congenital Heart Disease:
* Residual defects or new problems after previous corrective surgery.
* Subsequent stages in planned staged surgeries.
4. Aortic Disease:
* Progression of distal aneurysms (e.g., aortic arch, descending aorta) after previous aortic surgery (e.g., ascending aortic replacement).
* Infection of prosthetic grafts or anastomotic problems.
5. Infection:
* Prosthetic valve endocarditis.
* Pacemaker/defibrillator lead infection requiring extraction and debridement.
* Mediastinal infection debridement.
6. Other:
* Recurrent cardiac tumors.
* Constrictive pericarditis requiring pericardiectomy (though sometimes possible via thoracotomy).
Postoperative Recovery:
* Recovery is typically longer and more difficult than after the first surgery.
* ICU stay may be prolonged.
* Pain management requirements are higher.
* Need for respiratory support is greater; weaning from ventilation may be slower.
* Risk of complications (bleeding, infection, heart failure, renal failure, atrial fibrillation, etc.) is higher, requiring close monitoring and aggressive management.
* Hospital stay is significantly extended.
* Rehabilitation is slower, requiring extended physical therapy and convalescence.
Important Recommendations:
* Choose an Experienced Center: Success rates are directly linked to the surgical team’s experience. Select a hospital and surgeon with extensive experience and a proven track record in complex cardiac surgery, especially redo operations.
* Thorough Communication: Have detailed discussions with your cardiac surgeon about the specific reason for surgery, detailed plan, expected risks and benefits, and alternatives (if any).
* Comprehensive Evaluation: Complete all necessary preoperative tests.
* Understand the Risks: Be clearly aware of and mentally prepared for the high risks.
* Patience in Recovery: Strictly follow medical advice, actively participate in postoperative treatment and rehabilitation, and be patient.
Summary:
Redo median sternotomy for cardiac surgery is one of the most technically demanding and highest-risk procedures in cardiothoracic surgery. Its core challenge lies in the severe adhesions and altered anatomy resulting from the prior surgery. Although safety has improved with technological advances (better imaging, femoral cannulation techniques, instruments) and accumulated surgeon experience, the risks remain significantly higher than for primary surgery. The decision requires extreme prudence, carefully weighing the necessity against potential risks, and must be performed by a senior team at a highly experienced center.
Part 2: The Sternal Saw in Redo Sternotomy
In cardiac surgery, the sternal saw is the key instrument used to divide the sternum (median sternotomy). During redo sternotomy, using the sternal saw is an extremely dangerous and technically demanding step, often representing one of the highest-risk phases of the entire procedure.
Here is essential information about the sternal saw in redo sternotomy:
1. Core Risks:
* Catastrophic Hemorrhage: This is the greatest risk. Due to dense adhesions formed after the initial surgery, the heart (especially the right ventricle), great vessels (ascending aorta, superior vena cava), or previous bypass grafts (especially venous grafts close to the inner sternal surface) may be directly adherent to the posterior sternal wall. The standard act of sawing through the sternum can easily directly lacerate these vital structures, causing immediate, massive, and uncontrollable bleeding, which is life-threatening.
* Sternal Fracture/Shattering: The sternum may have healed poorly (non-union) or have retained fixation wires from the first surgery, and the bone itself may be more fragile (especially in elderly or osteoporotic patients). Sawing again carries a high risk of causing the sternum to shatter or fracture, compromising postoperative stability and healing.
2. Special Strategies and Techniques for Using the Sternal Saw in Redo Sternotomy:
To avoid these catastrophic outcomes, experienced cardiac surgical teams employ a range of special precautions and techniques:
* Exhaustive Preoperative Imaging Assessment (Gold Standard: Enhanced CT Scan):
* Assess Adhesion Severity and Location: Determine the extent and density of adhesions between the heart, great vessels, grafts, and the posterior sternal wall.
* Measure Safe Distance: Crucially, assess if there is a separable plane (fat layer or loose tissue) between the heart/great vessels and the posterior sternum, and the thickness of this plane at different sternal levels (upper, middle, lower).
* Identify High-Risk Structures: Precisely locate structures dangerously adherent to the sternum (e.g., right ventricular outflow tract, ascending aortic aneurysm, venous bypass grafts).
* Plan the Sawing Path: Based on imaging, decide where to start sawing, the depth, speed, and method of division.
3. Types of Sternal Saws:
* Pneumatic/Electric Reciprocating Saw: Traditional and commonest. Cuts via rapid back-and-forth blade movement. Highest risk in redo cases; requires utmost caution.
* Pneumatic/Electric Oscillating Saw (Vibrating/Sagittal Saw): Blade moves with high-frequency lateral vibrations or small oscillations. Poses relatively less tearing force on underlying soft tissue compared to reciprocating saws, making it the preferred choice for redo sternotomies. Examples: Bojin Sagittal Saw.
* Ultrasonic Bone Cutter: Uses ultrasonic energy to fragment bone, causing minimal damage to vessels/nerves (soft tissue), offering precise cutting. However, cutting efficiency is lower (slower for thick, dense sternum), and equipment is expensive. May be used selectively in high-risk areas or very osteoporotic bone.