Septal myectomy/myotomy

Septal myectomy/myotomy

Anesthesia type	General endotracheal anesthesia
Airway	ETT
Lines and access	2+ PIVs, central venous access +/- Swan, arterial line
Monitors	Standard, arterial line, PA catheter, TEE
Primary anesthetic considerations
Preoperative	{{{considerations_preoperative}}}
Intraoperative
Postoperative	Disposition to ICU while sedated. Disposition with inotropy as patient is weaned from bypass
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Provide a brief summary here.

Overview

Myotomy and septal myectomy are surgical procedures used primarily to treat hypertrophic obstructive cardiomyopathy (HOCM). This condition is characterized by the thickening of the heart muscle, particularly the interventricular septum, which can obstruct blood flow.

Indications

• Hypertrophic obstructive cardiomyopathy (HOCM)
  • Autosomal dominant disorder characterized by hypertrophy of the LV
  • Symptoms: dyspnea, palpitations, arrhythmia, syncope, heart failure, stroke, and sudden death
  • Management of this condition can be medical, electrophysiological or surgical. This article will focus primarily on the open surgical technique
• Symptomatic left ventricular outflow tract (LVOT) obstruction with eventual development of LV systolic failure symptoms
• Severe mitral regurgitation due to systolic anterior motion (SAM) of the mitral valve
• Refractory symptoms despite medical management (e.g., dyspnea, syncope)

Surgical procedure

• TEE (transesophageal echocardiography) used intraoperatively to guide resection and assess results.
• CPB as a topic is beyond the scope of this article but will be discussed briefly with the general steps below
  1. Median sternotomy
  2. Exposure of the heart
  3. Aortic cannulation
  4. Right atrial cannulation
  5. Insertion of aortic root and the LV vent
  6. Resection of hypertrophic ventricular septum

Preoperative management

Patient evaluation

System	Considerations
Airway	Direct vs. indirect laryngoscopy
Neurologic	Paralysis, CPB
Cardiovascular	Biventricular function, valvular abnormalities, integrity of conduction and presence of arrhythmias
Pulmonary	Orthopnea, dyspnea on exertion. Assess ability to wean from ventilator and secure airway postoperatively
Gastrointestinal	Rule out esophageal abnormalities, varices, issues swallowing given TEE
Hematologic	Starting H/H for CPB management/sequestration/priming of CPB cannulas. Assess underlying coagulopathy or anticoagulation given need for CPB
Renal	Assess renal function(cardiac surgery holds increased risk of AKI)
Endocrine	Assess history of diabetes, preoperative A1C(CPB is associated with hyperglycemia. Hyperglycemia is associated with worsened outcomes)
Other

Labs and studies

• Cardiology Assessment: Detailed history and physical examination.
• Imaging: Echocardiogram to assess septal thickness and LVOT gradient. Cardiac MRI may also be used.
• Functional Testing: Stress testing to evaluate symptomatology and obstruction severity.
• Labs
  • CBC
  • CMP
  • Coagulation studies
  • Blood cultures
  • +/- TEG if patient has history of comorbid condition that affects coagulopathy

Patient preparation and premedication

• Continued use of beta-blockers or calcium channel blockers until surgery.
• Consider anxiolytics like midazolam.

Intraoperative management

Monitoring and access

• Standard ASA monitors
• Arterial line
• Central access CVP +/- PA pressures(indicated for RV or LV failure)
• Transesophageal echo(TEE)

Induction and airway management

• General anesthesia with endotracheal intubation.
• Propofol or thiopental may be used, with careful consideration of dose given the myocardial depressant effects and decreased afterload they cause. Etomidate is also an option given its relative lack of effect on the cardiovascular system.

Positioning

• Supine position for surgical access.
• Shoulder roll
• Arms tucked

Maintenance and surgical considerations

• LV systolic function in patients with HOCM are usually normal to supranormal with a high ejection fraction.
• Diastolic dysfunction in patients with HOCM is caused by decreased ventricular compliance and impaired ventricular relaxation.

• Promote:
  • Increased preload
    • Trendelenburg positioning may be used for episodes of hypotension
  • Adequate afterload

• Avoid:
  • Vasodilators
  • Decreases in SVR
  • Increased inotropy
  • Increased chronotropy
    • Can be treated in perioperative period with B-antagonists(ex. esmolol)
  • Outflow tract obstruction

*Interestingly, halothane has a good profile for patients with HOCM, given it decreases contractility and heart rate.

• Hypotension
  • Should be treated with increased intravascular volume and increased afterload
  • Avoid medications with B-agonist activity as they worsen LVOT obstruction due to positive chronotropy and inotropy caused by B-adrenergic agents.
  • Maintain NSR, as the noncompliant LV increasingly relies on atrial kick for adequate end-diastolic volume

Emergence

Transport to ICU while sedated, and often while intubated

Postoperative management

Disposition

• Intensive care unit (ICU) monitoring initially.
  • Often intubated
  • Frequently requiring pressors or inotropic agents post-CPB.
• Continuous ECG monitoring for arrhythmias.

Pain management

• Regional anesthetic techniques for sternotomy
• Long acting opiates(dilaudid or methadone)
• Tylenol
• Avoid NSAIDs given patients undergoing cardiac surgery are at higher risk for kidney injury and patients are often coagulopathic from CPB

Potential complications

While cardiac surgery is high risk in its nature, septal myectomy is relatively safe procedure with excellent outcomes in improving obstructive pathology and symptoms of sytolic heart failure. One retrospective study of 65 patients who underwent open SM found < 1.9% required pacemaker insertion of mechanical circulatory support.. In this study there was a median post op ICU stay of <24 hours, while the national average is > 48 hours. One other study paints a less rosy picture but study a more elderly population. They evaluated 156 patients who had undergone open SM and found < 2.9% mortality at post op day 30%, 11.9% of patients requiring permanent pacemaker insertion, 24% suffering from residual significant obstruction.

• Arrhythmias (atrial fibrillation, ventricular arrhythmias)
• Ventricular septal defect
• Mitral regurgitation
• Bleeding or pericardial effusion
• AV node block requiring pacemaker insertion
• CPB specific complications