748 Case Report on Anatomical Factors That Increase the Complexity of Septal Myectomy Surgery

Background Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiac disease characterised by myocardial hypertrophy in the absence of alternative causes. Most HCM patients have left ventricular outflow tract (LVOT) obstruction due to systolic anterior motion of the anterior mitral valve (MV) leaflet and interventricular septum thickening. Septal myectomy coupled with MV repair or replacement can resolve this obstruction. Case We present a 42-year-old female referred for septal myectomy and MV intervention. Preoperative investigations revealed significant obstruction, mild aortic regurgitation (AR), pectus excavatum with posterior displacement of the heart and a narrow ascending aorta (2cm in diameter). The latter complicates LVOT access and increases the risk of aortic valve (AV) damage during retraction. The multidisciplinary team (MDT) decided against replacing the AV and MV due to the patient's young age and warfarin-associated risks. When going on bypass the patient experienced atrial fibrillation and progressed to ventricular fibrillation (VF) following electrical cardioversion. The procedure was extended due to an unexpected subaortic membrane resection and the need for a maze procedure. Also, post-bypass imaging showed obstruction resolution but worsening of the AR (moderate), which prompted the MDT to opt for an AV replacement. However, it became apparent that the complexity of her anatomy would require extensive surgery, leading to the decision to not proceed. There was prolonged weaning off bypass the second time because the patient developed persistent VF. Clinical lessons In conclusion, a thorough assessment is required by a specialist MDT team to determine the optimal treatment for complex HCM patients.