Transaortic Extended Left Ventricular Septal Myectomy in an 11-Year-Old With HOCM

This is an 11-year-old boy with hypertrophic cardiomyopathy (HCM) and MYH-7 gene mutation. He has been on medical therapy with B-blockers but recently it was noticed progression of his symptoms especially during exertion. He experienced recurrent episodes of presyncope and chest pain while riding his bike. Transthoracic echocardiography showed severe septal hypertrophy with a thickness of over 3 cm especially at the basal and midventricular levels. At rest, there was no obvious gradient but with stress echocardiography, there was systolic anterior motion (SAM) of the anterior mitral valve leaflet and almost near left ventricular cavitary obliteration and a gradient over 60 mmHg in the left ventricular outflow tract (LVOT).

Cardiac MRI was performed for risk stratification. He was referred for extended left ventricular septal myectomy and placement of epicardial internal cardioverter defibrillator (ICD) for primary prevention.

Through a median sternotomy, direct pressure measurement prior to initiation of cardiopulmonary bypass, showed a 30-mmHg gradient across the LVOT with positive Brockenbrough-Braunwald-Monroe maneuver.

Cardiopulmonary bypass was initiated via an aortic and right atrial cannulation. Through a transaortic approach, an extended left ventricular septal myectomy was performed starting below the nadir of the right coronary cusp and was directed in an anticlockwise direction towards the commissure between the left and non-coronary cusps. Further resection was performed down in the midventricle to ensure complete elimination of the gradient. We were able to perform complete resection without the need for a concomitant transapical approach. The anterolateral papillary muscle of the mitral valve was mobilized as it was fused to the interventricular septum.

Post bypass repeat pressure measurement revealed no LVOT gradient and negative Brockenbrough maneuver. An epicardial ICD was then placed after hemostasis was achieved. The patient tolerated the procedure well and was extubated in the operating room, received no transfusions. He was discharged on the fourth postoperative day.

Pre-discharge echocardiography showed no LVOT obstruction, both at rest and with Valsalva’s maneuver. The aortic and mitral valves were competent and ventricular function was preserved. He was one much smaller dose of beta blocker therapy compared to preoperative period, with expectation to be weaned off completely in 3 months.

In conclusion, extended left ventricular septal myectomy is the gold standard for children with obstructive pattern of HCM and failed to respond to maximal medical therapy.
 

References

1. Said SM. Commentary: Extended left ventricular septal myectomy for hypertrophic cardiomyopathy: The nuts and bolts. J Thorac Cardiovasc Surg. 2020 May;159(5): e299-e300
2. Arghami A, Dearani JA, Said SM, O'Leary PW, Schaff HV. Hypertrophic cardiomyopathy in children. Ann Cardiothorac Surg. 2017 Jul;6(4):376-385
3. Said SM, Schaff HV. Surgical treatment of hypertrophic cardiomyopathy. Semin Thorac Cardiovasc Surg. 2013 Winter;25(4):300-9
4. Said SM, Schaff HV, Abel MD, Dearani JA. Transapical approach for apical myectomy and relief of midventricular obstruction in hypertrophic cardiomyopathy. J Card Surg. 2012 Jul;27(4):443-8.

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