Hensley's Practical Approach to Cardiothoracic Anesthesia

16. Anesthetic Considerations for Surgical Myectomy in Patients With Hypertrophic Cardiomyopathy 353

Although the operation is technically more challenging in children because of the difficulty of exposure of the smaller structures, there is a role for surgery in the pediatric group with similarly acceptably low-risk and good late results. Late survival after myec tomy is improved compared to the natural history of this disease without surgery. Anes thetic management of surgical myectomy for HCM in children, particularly induction of general anesthesia, is more challenging than in adults. Preoperative hydration is essential. Some experts recommend admission of children to the hospital for IV hydration before the day of surgery. Placement of preinduction arterial lines in children is seldomly pos sible. Also, inhalation induction with a higher dose of volatile agent common in pediatric practice might compromise cardiac output due to decreased systemic vascular resistance and exacerbation of LVOT obstruction. Larger doses of oral premedication (midazolam 0.5-1 mg/kg, ketamine 3-5 mg/kg) may help before induction. IV induction is utilized when peripheral IV can be placed without upsetting the child. Otherwise, gentle inhala tion induction with sevoflurane not exceeding 4% can facilitate peripheral IV placement. IV fluids and phenylephrine should be readily available to maintain preload and vascular resistance during and after induction. The rest of anesthetic management is similar to the adult population. Pecto-intercostal fascial nerve blocks can be used for teenagers or older children, alternatively younger children receive wound local anesthetic infiltration by the surgeon. D. Right Ventricular Hypertrophy Right ventricular hypertrophy may rarely occur with HCM, 27 and some young patients may present with both LVOT and right ventricular outflow tract obstruction. Right ventricular enlargement and dysfunction are associated with worse prognosis. 28 Patients with right ven tricular obstruction may require right ventricular myectomy and outflow patch augmentation in addition to LV myectomy. In these patients, inotropic support might be necessary early postoperatively following bilateral ventriculotomy. V. Summary Extended septal myectomy can be performed in symptomatic patients with HCM with very low mortality and excellent relief of symptoms. Early significant reductions in LVOT obstruction and degree of MR are maintained at late follow-up in the majority of patients. Anesthetic management of surgical myectomy is challenging but rewarding. While severe hemodynamic swings are com mon, they usually respond well to maneuvers, alleviating dynamic LVOT obstruction. At the end of the myectomy operation, the immediate result can be appreciated with the direct measurements of absent or minimal LVOT gradient and improvement of pulmonary pressure. REFERENCES 1. Maron BJ, Gardin JM, Flack JM, Gidding SS, Kurosaki TT, Bild DE. Prevalence of hypertrophic cardiomyopathy in a general population of young adults. Echocardiographic analysis of 4111 subjects in the CARDIA Study. Coronary Artery Risk Devel opment in (Young) Adults. Circulation . 1995;92(4):785-789. 2. Semsarian C, Ingles J, Maron MS, Maron BJ. New perspectives on the prevalence of hypertrophic cardiomyopathy. J Am Coll Cardiol . 2015;65(12):1249-1254. 3. McKenna WJ, Maron BJ, Thiene G. Classification, epidemiology, and global burden of cardiomyopathies. Circ Res . 2017;121(7):722-730. 4. Sun D, Schaff HV, Nishimura RA, Geske JB, Dearani JA, Ommen SR. Transapical septal myectomy for hypertrophic cardio myopathy with midventricular obstruction. Ann Thorac Surg . 2021;111(3):836-844. 5. American College of Cardiology Foundation/American Heart Association Task Force on Practice, American Association for Thoracic Surgery, American Society of Echocardiography, et al. 2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. J Thorac Cardiovasc Surg . 2011;142:e153-e203. 6. Peng L, Burczak DR, Newman DB, Geske JB. Repetitive squat-to-stand provocation of dynamic left ventricular outflow tract obstruction in hypertrophic cardiomyopathy. J Am Soc Echocardiogr . 2022;35(3):323-326. 7. Maron BJ, Roberts WC. Hypertrophic cardiomyopathy and cardiac muscle cell disorganization revisited: relation between the two and significance. Am Heart J . 1981;102(1):95-110. 8. Tanaka M, Fujiwara H, Onodera T, Wu DJ, Hamashima Y, Kawai C. Quantitative analysis of myocardial fibrosis in normals, hypertensive hearts, and hypertrophic cardiomyopathy. Br Heart J . 1986;55(6):575-581.

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