M · E · S · M
Minimally Invasive Electro Septal Myectomy
The world's largest single-center series of minimally invasive septal myectomy for hypertrophic cardiomyopathy, via right infra-axillary incision with transaortic approach.
Zhejiang Provincial People's Hospital, Hangzhou, China
Surgery without visible scars
A 5cm incision hidden in the right axilla — completely concealed beneath the arm's natural resting position. No bone cutting. No muscle division. No rib resection. Invisible in any clothing. The transaortic approach avoids the long-term uncertainties on mitral valve function associated with a trans-mitral route.
Why MESM
MESM bridges the traditional Morrow procedure with the advancements of minimally invasive surgery — offering a unique combination of visualization, instrumentation, and comprehensive repair capability.
Comprehensive LVOT management
MESM bridges the traditional Morrow procedure with the advancements of minimally invasive surgery. It addresses the full spectrum of obstructive HCM — including patients with mild-to-moderate septal hypertrophy but severe outflow tract obstruction driven by mitral and subvalvular anatomy. All procedures are performed through the same right axillary approach, in a single operation.
See better, work better.
Endoscopic visualization through the right axillary approach provides an unprecedented direct view of all left ventricular structures — septum, papillary muscles, chordae, and mitral leaflets — enabling comprehensive assessment and repair in a single view. This perspective is unique to the MESM approach and has not been previously described.
Clinical outcomes
Peer-reviewed publications, international conference presentations, and outcomes from the world's largest single-center minimally invasive HCM surgery program.
The complete MESM ecosystem
Surgery, echocardiographic diagnosis, and perioperative care — integrated into a single, seamless pathway from evaluation to recovery.
For surgeons & referring physicians
The operative essentials of minimally invasive septal myectomy, how to refer a case for review, and how to arrange observation.
A transaortic modified Morrow procedure, reached without dividing the sternum:
Why the approach helps. The right axilla gives a direct line of sight to the left ventricular apex, and reported superior exposure of the interventricular septum compared with median sternotomy. The septum presents as a triangular surface spread above the field; lifting its proximal portion allows the distal septum to fall under gravity, so resection runs in a controlled proximal-to-distal direction. Because the assistants share the surgeon's view — difficult through a sternotomy — the operation is also more teachable.
Why electro-excision helps. In the conventional technique the septum is held in forceps and cut with scissors or a blade; after the first piece is taken the remaining muscle is friable, difficult to grasp, and the cut surface fragments. Electro-excision needs no traction — the hook divides the muscle from the periphery inwards — so the specimen is much more often removed en bloc. The uneven bed left behind, which is hard to trim with a blade, is then smoothed with the same instrument: the tissue in contact is vaporised, giving a polished surface with no fragments left in the ventricle.
Operative rationale as described in JTCVS Techniques 2024 (n=148) and Ann Thorac Surg 2025 (n=100). Comparative trials against sternotomy myectomy have not been performed; these are mechanistic and observational findings.
We are glad to review imaging for patients with symptomatic obstructive HCM, including cases judged difficult for a catheter-based approach or for conventional access.
Reviews are collegial and non-binding — the referring team retains care of the patient.
Surgeons wishing to see the approach in practice are welcome to enquire about visiting observation, and about collaboration on data and technique.
Published series, operative detail and conference presentations are summarised in the Evidence section.
Operative images: Heart Center, Zhejiang Provincial People's Hospital.
Common questions
For patients and referring physicians — what the operation is, how it compares with the traditional Morrow procedure and alcohol septal ablation, and what to expect.
Septal myectomy is open-heart surgery for hypertrophic obstructive cardiomyopathy (HOCM), in which the thickened muscle of the interventricular septum is removed to relieve obstruction of the left ventricular outflow tract (LVOT). It is the most established form of septal reduction therapy and, in experienced centres, durably relieves obstruction and the symptoms it causes — breathlessness, chest pain and fainting.
The Morrow procedure is the classic transaortic septal myectomy, traditionally performed through a median sternotomy (a full breastbone incision). MESM — Minimally Invasive Electro Septal Myectomy — is a modified Morrow procedure performed through a hidden 5 cm incision below the right armpit, in the 3rd intercostal space, using electrocautery to sculpt the septum. The operation and its goal are the same as Morrow's; the access route and the instrumentation are what differ.
The muscle resection itself follows the same transaortic principles. The difference is access: instead of dividing the breastbone, the heart is reached through a small incision hidden beneath the arm. The sternum is left intact and no scar is visible on the chest. Avoiding sternotomy is generally associated with less surgical trauma to the chest wall and no restrictions related to breastbone healing; individual recovery still depends on the patient and the complexity of the operation.
Both are septal reduction therapies for drug-refractory obstructive HCM. Surgical myectomy removes the obstructing muscle directly under vision and can address associated problems in the same operation — the mitral valve, papillary muscles, and mid-ventricular obstruction. Alcohol septal ablation is catheter-based and depends on suitable coronary septal anatomy. Major guidelines generally favour surgical myectomy for younger patients and for anatomy that ablation cannot reach, while ablation is an option for patients at high surgical risk. The right choice is individual and should be made with an experienced HCM team.
Typical candidates have symptomatic obstructive HCM with significant LVOT obstruction that persists despite medication. Suitability for the trans-axillary minimally invasive approach also depends on individual anatomy and any concomitant procedures required. Assessment relies on echocardiography and cross-sectional imaging; send your imaging and clinical summary for review to find out whether the approach is appropriate for you.
Because the breastbone is not divided, there is no sternal wound to heal, and the single 5 cm incision sits beneath the arm where it is hidden in normal posture and clothing. Most patients begin mobilising early in a standard postoperative pathway. Length of stay and return to activity vary with the individual and with what was done during the operation, so your own timeline should be discussed with the surgical team.
General information only — not a diagnosis or treatment recommendation for any individual. Please discuss your own situation with a qualified cardiac team.
Whether you're a patient seeking treatment or a surgeon interested in MESM training, we'd like to hear from you.
