Novel technique for extended septal myectomy using a microdebrider

Safe way of performing extended septal myectomy using the Medtronic Microdebrider.

Central Message.

We describe an innovative and safe way to perform extended septal myectomy using the Medtronic Microdebrider.

Septal myectomy is indicated in patients with hypertrophic obstructive cardiomyopathy (HOCM) who have severe symptoms despite medical therapy. It has been shown to improve survival and symptoms.¹ We present an innovative technique used to perform the procedure.

Clinical Scenario

Informed consent was obtained from the patient for this retrospective reporting; institutional review board approval was not required per institution. The patient was a 49-year-old man with HOCM. His main symptoms were recurrent syncope and exertional dyspnea. Transthoracic echocardiogram demonstrated left ventricular ejection fraction of 60% with no valvular abnormalities, asymmetrical left ventricular hypertrophy (LVH) with maximal thickness of 18 mm at the LV septal wall and systolic anterior motion with a left ventricular outflow tract (LVOT) peak gradient of 143 mm Hg at rest. He was offered septal myectomy in view of high LVOT gradient and severe symptoms despite taking beta-blockers and disopyramide.

Surgical Technique

After general anesthesia, preprocedure transesophageal echocardiogram was performed to evaluate the LVOT peak gradient, septal hypertrophy, and mitral valve abnormalities. After median sternotomy and pericardiotomy, the ascending aorta and right atrium were cannulated for cardiopulmonary bypass. LV vent was inserted via the right superior pulmonary vein. Following clamping of the aorta, myocardial protection was achieved by blood cardioplegia given in the aortic root. A transverse aortotomy was performed and carried down toward the noncoronary sinus. The aortic valve leaflets were retracted aside. Classic Morrow incisions were made using a #10 knife blade with initial resection of an 8-mm thick LVOT flap. This was further deepened using a Medtronic Straightshot M4/M5 Microdebrider with a Medtronic 4.0 mm RAD 40 curved rotatable blade with automated electromagnetic tracking.² The resection margin was then extended to the LV free wall and medially to excise the septal scar. The resection surface was palpated and smoothened with the Microdebrider. Any abnormal attachments between the anterolateral papillary muscle and the ventricular septum were then excised. The aortotomy was closed and patient was weaned off cardiopulmonary bypass (Video 1). We have successfully performed 3 extended septal myectomies using this technique (Table E1).

Discussion

The Microdebrider is an instrument used commonly in sinus surgery by otolaryngologists and is suitable for precise incisions and removal of soft tissue, hard tissue, or bone. The Microdebrider is powered by an integrated power console system and is operated using a foot pedal. The blade is connected to an ergonomic handpiece for easy handling. Suction and irrigation are also integrated into the device to allow for removal of the debris to prevent clogging up of the blade (Figure 1). The consumables of the device, including the blade and tubing cost only about USD$283.

Figure 1.

A, The Medtronic M5 Microdebrider with RAD 40 curved blade attached. B, Close-up view of the tip of the 4 mm cutting blade. C, The M5 Microdebrider handpiece with all the tubing and blade attached and labeled.

We used a 11 cm 40° blade which allowed 360° rotation, and this in addition to its angulation, resulted in flexibility to reach areas that the standard blade cannot reach. This can be further facilitated by pushing the right ventricle posteriorly using a sponge forceps (Figure 2). The tip of the Microdebrider is 4 mm, which allows for gradual resection of 1 to 2 mm of muscle each time with proper control.

Figure 2.

The 11 cm Medtronic Microdebrider with 360° rotatable blade can reach every part of the left ventricular wall.

In a myectomy performed using a blade, one must be very careful not to damage any structures when going through the aortic valve, performing the myectomy, and removing the blade. The surgeon may also hurt himself or his staffs with the blade. Furthermore, attempts to further deepen the septal incision on cut muscle using the blade may be challenging and the resultant loose muscle pieces may embolize.³ The Microdebrider only cuts where the opening of the blade is directed and when activated by the foot pedal, adding safety and accuracy to the procedure. Use of the Microdebrider also makes deepening incisions easy and intuitive, and the suction reduces the risk of embolism.

However, there are some limitations with this technique. Firstly, the surgeon is unable to know how much muscle is resected during the procedure because all the debris is suctioned away. Secondly, there is a learning curve. We had a case of aortic valve injury because the foot pedal was not released during withdrawal of the Microdebrider. The valve cusp was caught by the Microdebrider and partially detached from the annulus. Fortunately, this was successfully repaired using a bovine pericardial patch.

Greater reduction in LVOT gradient is associated with better improvement in postoperative functional class status.⁴ One main reason for residual gradient is inadequate resection at the midventricular level.⁵ The Microdebrider allows for better reach and precise resection to produce good and reproducible results with little added cost.

Appendix E1

Table E1.

Results of patients treated with septal myectomy performed using the Medtronic Microdebrider

Characteristic	Patient 1	Patient 2	Patient 3
Age (y)	36	49	27
Gender	Female	Male	Male
Redo operation	No	No	Yes
Preoperative LVOT gradient (mm Hg)	78	143 at rest 196 with Valsalva	81 at rest 118 with Valsalva
Preoperative septal thickness (mm)	14	18	16
Preoperative mitral regurgitation and SAM	Moderate with SAM	Mild-moderate with SAM	Moderate-severe with SAM
Postoperative LVOT gradient (mm Hg)	11	11	13
Postoperative septal thickness (mm)	11	11	8-12
Postoperative mitral regurgitation and SAM	Mild, no SAM	Trivial, no SAM	Mild, no SAM
Postoperative atrial fibrillation	Yes	Yes	No
Perioperative cerebral vascular accident	No	No	No
Ventricular septal defect	No	No	No
Permanent pacemaker placement	No	No	No
Other complications	No	Aortic valve injury repaired using bovine pericardial patch	No
Duration of hospital stay (d)	8	8	20

LVOT, Left ventricular outflow tract; SAM, systolic anterior motion.

Supplementary Data

Video 1

Extended septal myectomy performed using the Medtronic Microdebrider. Video available at: https://www.jtcvs.org/article/S2666-2507(23)00197-9/fulltext.