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
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