**7. Alterantive surgical options to septal myectomy**

### **7.1 Mobilization of the right and left fibrous trigones**

Yacoub et al. has pioneered this technique as an alternative to septal myectomy in those with obstructive type of HCM [21]. It is based on the role of the right and left fibrous trigones in the functional anatomy of the LVOT. The authors proposed that LVOTO is secondary to connection of the both the right and left fibrous trigones by a complete fibromuscular ring which is needed to be excised and both trigones be mobilized to ensure complete relief of the LVOT gradient.

After resection of a fibromuscular wedge of tissue from the interventricular septum, the left fibrous trigone is mobilized be extending the incision laterally to open the hinge mechanism between the septum and the subaortic curtain. Mobilization of the right fibrous trigone is done by excision of a wedge of abnormal tissue in the angle between the membranous septum and the subaortic curtain.

#### **7.2 Modified Konno procedure**

While extended left ventricular septal myectomy is considered the gold standard surgery for HCM with obstruction, the procedure is quite challenging in young children and in those with right ventricular outflow tract (RVOT) obstruction.

Modified Konno emerged as an alternative and another tool in the box for some of these cases. The procedure is performed after cardioplegic arrest by making a transverse incision in the (RVOT) and through the aortotomy, a right-angled instrument is passed and used to perforate the interventricular septum. This provides the upper limit for the septal incision. The conal septum is then incised towards the apex and away from the conduction tissue. Myectomy is performed on both sides of the septum, followed by patch closure of the created ventricular septal defect.

The long-term results of modified Konno have been reported in 79 patients with 38% of them below the age of five years, and 25% had Noonan syndromes with RVOTO present in 28% of them. Survival without death or transplantation was 82% at 20 years [22].
