Hensley's Practical Approach to Cardiothoracic Anesthesia

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III. Cardiac Anesthesia

LVOT obstruction is common in HCM and frequently is a driver of symptoms. Transaortic septal myectomy is most often indicated in patients with obstructive HCM who continue to have limiting symptoms despite medical treatment (ie, β-blockade, calcium antagonists, disopyramide, mavacamten). The anesthetic management of surgical myectomy for HCM may be challenging due to labile loading conditions leading to blood pressure swings. This chapter reviews the physiologic implications of HCM and the practical approach to the perioperative management of these patients. II. Hypertrophic Cardiomyopathy A. Epidemiology, Morphology, Histopathology, Genetics 1. Epidemiology Epidemiologic studies indicate that HCM affects ∼ 600,000-700,000 individuals in the United States alone; many people, such as asymptomatic family members, remain undiag nosed; therefore, the true prevalence of HCM in the general population might be underes timated. HCM is a global disease, particularly prevalent in Asia (China and Japan), Western Europe, and North America. 5 2. Morphology Asymmetric septal hypertrophy is the most common form of HCM, often manifesting with a sigmoid septum, wherein the basal interventricular septum is the thickest opposite to the anterior leaflet of the mitral valve in its open position. This results in subaortic obstruction, which may be limited to the immediate subaortic area (Figures 16.1B, 16.2A) or may extend

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FIGURE 16.1 Morphologic variants of hypertrophic cardiomyopathy. (A) Normal left ventricle. (B) Basal septal hy pertrophy. (C) Midventricular septal hypertrophy. (D) Apical hypertrophy. (From Kotkar KD, Said SM, Dearani JA, Schaff HV. Hypertrophic obstructive cardiomyopathy: the Mayo Clinic experience. Ann Cardiothorac Surg . 2017;6(4):329-336. Figure 1. Used with permission of Mayo Foundation for Medical Education and Research. All rights reserved.)