Transaortic extended septal myectomy
Under general anaesthesia, the heart and ascending aorta were exposed by a median incision with sternotomy, and cardiopulmonary bypass was performed using ascending aortic cannulation. Through a transverse aortotomy, the aortic valve was exposed totally after cardiac asystole induced with cold blood cardioplegia. The aortic leaflets were retracted by the assistant so as to inspect the LVOT, the hypertrophic cardiac muscle and anterior mitral valve leaflet. For better exposure through the aortic incision, we used two long retractors and a suction pump that could suck the blood in the LV and retract the aortic valve simultaneously (Figs 1–3). It is also important for the surgeon to have a head lamp. Moreover, it is usually necessary to use a medical gauze ball as a depressor to press the hypertrophic muscle from outside the heart, so better exposure can be gained and resection carried out more easily. Additionally, two homemade long-handled scalpels (one sharp, the other bush-hook) with a length of ∼30 cm and a long pair of surgical forceps (∼32 cm long) were used during the resection.
Figure 1: Abnormal muscle located between the anterior papillary muscle and the anterior leaflet of the mitral valve.
Figure 2: The abnormal muscle bundle was cut off.
Figure 3: Hypertrophic IVS was partially resected.
The aim was to open the LVOT and reduce the gradient to <30 mmHg, which often required resection of the hypertrophic muscle until the thickness of the LV wall and interventricular septum became nearly normal by visual inspection. By looking through the incision of the aortic root, we could often see the papillary muscles’ bases after TAESM was completed. Accordingly, the extended septal myectomy in this cohort was a much more extensive resection (Figs 4–6) compared with the original Morrow procedure described almost half a century ago [9]. To some extent, one of the most important tips of our surgical technique was to define the resection border precisely and try to resect the hypertrophied muscles as a whole mass (Fig. 6). The extent of resection could be distally to or sometimes beyond the level of the mitral papillary muscles towards the apex (Fig. 4). The most distal portion of the obstruction must be resected completely despite the difficulty in exposing the distal part of the LV cavity [10]. In order to open the LVOT thoroughly, aberrant muscle bundles must be resected, which might be located around the root of papillary muscles, between the apex and the left ventricular free wall, or between papillary muscles and free wall, etc (Fig. 5). To obtain a more posterior position, partial excision of the papillary muscles off the left ventricular wall was necessary. Moreover, mitral valve repair, such as anterior leaflet folding when redundancy existed, was another important procedure in special patients who had slack chordae and leaflets, which might result in systolic anterior motion (SAM). The adequacy of the resection was evaluated by direct inspection, and intraoperative TEE evaluation was carried out immediately after the patient was weaned from cardiopulmonary bypass. Some concomitant surgical procedures had been administrated to the patients who had cardiac comorbidities, including coronary artery bypass grafting (CABG), modified Maze procedure, valve repair, plasty or replacement surgery, enlargement of right ventricular outflow tract (RVOT) and cardiac tumour resection.
Figure 4: The drawings show the extent of resection. We often try to resect the hypertrophied muscles as a whole mass.
Figure 5: The drawings show the extent of resection, including abnormal muscles that are located between the anterior papillary muscle and the anterior leaflet of mitral valve.
Figure 6: The resected muscle sample weighed 6.2 g (about 4 cm × 2 cm × 1.5 cm).
After the operation, temporary pacing wires were placed on the LV as a routine procedure.