Comprehensive Guide to Septal Myectomy: What Surgeons Need to Know

Overview Septal myectomy is a highly specialized surgical procedure used to treat hypertrophic obstructive cardiomyopathy (HOCM), a condition characterized by abnormal thickening of the heart muscle, particularly the interventricular septum, which can obstruct blood flow from the left ventricle. This procedure aims to relieve left ventricular outflow tract (LVOT) obstruction by removing a portion of the thickened septal muscle, thereby improving cardiac function and alleviating symptoms.

Indications Septal myectomy is primarily indicated for patients with symptomatic HOCM who do not respond adequately to medical therapy, such as beta-blockers, calcium channel blockers, or disopyramide. Patients typically present with symptoms such as dyspnea, chest pain, syncope, or palpitations. The procedure is particularly recommended for those with severe LVOT obstruction (peak gradient > 50 mmHg) or those at high risk for sudden cardiac death. It may also be considered in patients with recurrent heart failure or arrhythmias despite optimal medical treatment.

Preoperative Evaluation A thorough preoperative evaluation is crucial to identify suitable candidates for septal myectomy and to plan the surgery. This evaluation typically includes:

• Echocardiography: This is the cornerstone of preoperative assessment, allowing for the measurement of septal thickness, LVOT gradient, and the presence of mitral valve abnormalities or systolic anterior motion (SAM) of the mitral valve.
• Cardiac MRI: Provides detailed images of the heart's structure, helping to further assess the extent of myocardial hypertrophy and fibrosis.
• Electrocardiogram (ECG): Detects arrhythmias, particularly atrial fibrillation or ventricular arrhythmias, which are common in HOCM patients.
• Exercise Stress Testing: Assesses functional capacity and the dynamic nature of LVOT obstruction.
• Coronary Angiography: Performed in patients over 40 years or those with risk factors for coronary artery disease (CAD) to rule out concomitant CAD.
• Genetic Testing: May be recommended, particularly in younger patients, as HOCM is often hereditary.

Contraindications While septal myectomy is a life-saving procedure for many, it is not suitable for all patients. Contraindications include:

• Mild or asymptomatic HOCM: Patients with minimal symptoms can often be managed medically.
• Severe comorbidities: Conditions such as advanced lung disease or severe renal impairment may increase surgical risks to an unacceptable level.
• Non-obstructive hypertrophic cardiomyopathy: In patients without significant LVOT obstruction, other treatments, such as alcohol septal ablation or heart transplantation, may be more appropriate.
• Inadequate septal thickness: If the septum is not sufficiently thick to allow for safe resection, alternative therapies should be considered.

Surgical Techniques and Steps Septal myectomy is a complex procedure that requires a highly experienced cardiac surgical team. The surgery is typically performed under general anesthesia through a median sternotomy. The key steps include:

1. Preparation and Cardiopulmonary Bypass (CPB): The patient is placed on CPB to allow for a bloodless surgical field.
2. Aortotomy: The ascending aorta is opened to provide access to the left ventricular outflow tract.
3. Exposure of the Septum: The surgeon visualizes the hypertrophied septum through the aortic valve.
4. Resection of the Septum: A portion of the thickened septal muscle is excised, typically from the base of the anterior septum to the apex, with care taken to avoid damage to the conduction system or the mitral valve apparatus.
5. Mitral Valve Repair (if necessary): If mitral valve abnormalities such as SAM are present, additional procedures like mitral valve repair or replacement may be performed.
6. Closure and Weaning from CPB: The aortotomy is closed, and the patient is weaned from CPB while monitoring for hemodynamic stability and the resolution of LVOT obstruction.
7. Transesophageal Echocardiography (TEE): Post-resection, TEE is used intraoperatively to confirm the effectiveness of the myectomy and to ensure that there are no residual gradients or complications such as ventricular septal defect (VSD).

Postoperative Care Postoperative management focuses on monitoring for complications, promoting recovery, and preventing recurrence of symptoms. Key aspects include:

• Intensive Care Monitoring: Patients are usually transferred to the ICU for close monitoring of cardiac function, hemodynamics, and potential complications.
• Pain Management: Adequate pain control is essential to facilitate early mobilization and recovery.
• Arrhythmia Surveillance: Continuous ECG monitoring is necessary to detect arrhythmias, which are common after septal myectomy. Anti-arrhythmic medications or temporary pacing may be required.
• Fluid and Electrolyte Management: Careful management of fluids and electrolytes helps to prevent fluid overload and maintain optimal cardiac output.
• Early Mobilization and Rehabilitation: Encouraging early ambulation and participation in cardiac rehabilitation programs can improve outcomes and reduce the risk of complications such as deep vein thrombosis (DVT).
• Long-term Follow-up: Patients require lifelong follow-up with regular echocardiograms to monitor for recurrence of LVOT obstruction and to assess for any late complications.

Possible Complications As with any major surgery, septal myectomy carries risks of complications, including:

• Bleeding: Both intraoperative and postoperative bleeding can occur, particularly due to the vascular nature of the myocardium.
• Infection: Sternal wound infections or endocarditis are potential risks, necessitating sterile techniques and prophylactic antibiotics.
• Arrhythmias: Atrial fibrillation is common postoperatively, and there is also a risk of ventricular arrhythmias or heart block, which may require pacemaker implantation.
• Ventricular Septal Defect (VSD): Inadvertent perforation of the septum during resection can lead to a VSD, which may require surgical repair.
• Mitral Valve Complications: Damage to the mitral valve or its apparatus can result in mitral regurgitation, sometimes necessitating further surgery.
• Heart Failure: Although rare, some patients may experience worsening heart failure after surgery, requiring intensive management or even heart transplantation.

Different Techniques While the classic approach to septal myectomy involves resection through the aortic valve, variations exist based on the specific anatomy and pathology of the patient:

• Transapical Myectomy: This approach involves accessing the septum through an incision at the apex of the heart, allowing for a more extensive resection in patients with mid-ventricular obstruction.
• Extended Myectomy: This involves a more extensive resection of the septum and is often combined with procedures to address mitral valve abnormalities.
• Minimally Invasive Techniques: Although less common, minimally invasive approaches using smaller incisions or robotic assistance are being explored, particularly in centers with extensive experience.

Prognosis and Outcome The prognosis after septal myectomy is generally excellent, with significant improvement in symptoms and quality of life. The majority of patients experience relief from LVOT obstruction, with a marked reduction in the risk of sudden cardiac death. Long-term survival rates are high, with many patients leading normal, active lives post-surgery. However, careful follow-up is essential to monitor for recurrence of obstruction or the development of new cardiac issues.

Alternative Options For patients who are not candidates for septal myectomy or prefer less invasive options, alternatives include:

• Alcohol Septal Ablation: A catheter-based procedure that involves injecting alcohol into the septal artery to induce a localized infarction, thinning the septum.
• Dual Chamber Pacing: This involves the implantation of a pacemaker to alter the timing of ventricular contraction, thereby reducing obstruction.
• Medications: In less severe cases, symptoms can be managed with medications like beta-blockers, calcium channel blockers, or disopyramide.

Average Cost The cost of septal myectomy can vary widely depending on the region, hospital, and specific patient factors. In the United States, the total cost, including preoperative evaluation, surgery, hospitalization, and postoperative care, can range from $30,000 to $60,000. This figure may be lower in other countries or higher in high-cost areas or prestigious institutions.

Recent Advances Recent advances in septal myectomy include:

• 3D Echocardiography: Improved imaging techniques allow for better preoperative planning and intraoperative guidance, reducing complications and improving outcomes.
• Genetic Research: Advances in genetic testing and understanding of the molecular basis of HOCM are helping to identify patients at risk earlier and tailor treatments more effectively.
• Minimally Invasive Surgery: As mentioned earlier, minimally invasive approaches are being refined, potentially offering reduced recovery times and complications.
• Hybrid Procedures: Combining septal myectomy with other cardiac surgeries, such as valve repair or coronary artery bypass grafting (CABG), is becoming more common in complex cases.