Surgical Ventricular Septal Myectomy for Patients With Noonan Syndrome and Symptomatic Left Ventricular Outflow Tract Obstruction

Approximately 20% to 30% of patients with Noonan syndrome (NS) have asymmetric left ventricular hypertrophy (LVH) and LV outflow tract obstruction (LVOTO). The role of surgical myectomy in such patients is unknown. We sought to compare clinical features and outcomes of patients with NS and LVOTO with age- and gender-matched patients with nonsyndromic, obstructive hypertrophic cardiomyopathy (HC) after myectomy. Two cohorts were selected and retrospectively analyzed using Mayo Clinic databases from 1996 to 2014. Subjects included patients with NS with LVH and LVOTO and nonsyndromic controls with obstructive HC. Twenty-three patients with NS and LVH were identified, of whom 12 (8 males) underwent myectomy (10 septal and 2 combined septal/apical) for severe LVOTO (10 pediatric and 2 adults; 13 ± 10 year old [range 1 to 39]). Similar echocardiographic improvements were noted in both groups. There were no perioperative deaths. Residual gradients were slightly higher in patients with NS. No improvement was noted in left atrial volume after myectomy in patients with NS. At early follow-up, the majority showed improvement in the New York Heart Association class (88% in NS vs 82% in HC, median of 6 and 2 months, respectively). At late follow-up (median of 7 years), the survival rate was 92% in NS and 100% in HC. In patients with NS with LVH and symptomatic LVOTO, myectomy reduces both gradient and the New York Heart Association class, similar to patients with nonsyndromic obstructive HC. Residual gradients were slightly higher, and left atrial dilation persisted in patients with NS. In conclusion, myectomy should be considered in patients older than 1 year with NS and symptomatic LVOTO.