Septal Myectomy

Airway: ETT
Access: Large IV, arterial line, CVC, +/- sheath
Pain: Moderate
Position: Supine, arms tucked
Time: 3-6 hours
Blood Loss: G+H required
Special:

  • LVH
    • Usually good systolic function
    • Harder myocardial protection
    • DCC less effective
  • High risk dynamic LVOTO
  • CPB with high potential for repeat bypass runs
  • Provocation maneuvers Requires assess the extent of LVOTO under exercise conditions.
  • Complex TOE exam

Open-heart surgical procedure to treat HOCM/HCM by resecting the basal IVS, ↑ the diameter of the LVOT and ↓ turbulent flow and the gradient through the LVOT. Patients will typically:

Surgical Stages

  • Sternotomy
  • Establish CPB
    • Pre-operative provocation testing can be done if required (i.e., if resting gradients or MR are not severe)
  • Aortotomy and septal resection
  • Wean and assess extent of resection
    Re-measure and re-provoke.
  • Potential return to CPB and further resection
  • Re-wean, re-assess, and re-re-provoke
  • Chest closure

Preoperative

Assessment:

  • Exercise tolerance and symptoms
  • Echo: Severity of obstruction and MR
  • MRI: Septal width

Premedication:

  • Usual to withhold beta-blockers and CCBs on day of surgery to allow adequate provocation

Intraoperative

Avoid provocation maneuvers without the ability to immediate institute CPB (i.e., heparinised with cannulas in situ)

Preparation:

Precipitants for LVOTO are:

  • ↑ HR
  • ↑ Inotropy
  • ↓ Preload
  • ↓ Afterload

We want to avoid this in induction, and precipitate it for provocation testing. This requires careful control of volume and avoidance of long-acting agents.

  • Standard cardiac draw
  • Provoking agent
    • Dobutamine 10-40ug/kg/min
    • Isoprenaline 5-20ug/kg/min
  • Pressure monitoring lines
    Consider two additional transducers for calculating direct LVOT gradients:
    • Direct ventricular pressure
      Via 18G needle.
    • Aortic pressure
      Via root vent.

Echocardiography:

  • Interventricular septum
    • Septal width
      • Particularly basal septum.
      • Separate measurements for inferoseptal and anteroseptal walls
        Consider Multiplanar Reconstruction for good alignment.
    • Distance from AV annulus to maximal septal thickening
  • Mitral valve
    • Degree of MR
    • Risk of SAM
      • C-sept
      • AMVL length
  • LVOT
    • Gradient

Provocation:

  • ↑ Dobutamine/isoprenaline until pathophysiology is observed or maximal heart rate is reached
  • Considerations for further resection:
    • LVOT gradient >30mmHg
    • MR ≥ moderate

Emergence:

  • Post-bypass TOE:
    • VSD
    • AV injury
      AR.
    • Coronary-cameral fistula
      Unroofing of septal perforators, causing bleeding into LV. Must be distinguished from a VSD but is otherwise benign.

References