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Also called Idiopathic Hypertrophic Subaortic Stenosis (IHSS).

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Etiology

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  • Autosomic dominant with variable genetic penetrance
  • Highest incidence in 13–22 years old
  • Males = females
  • Highest incidence of sudden cardiac death (SCD) in all patients
  • Features (Figure 20-1):
    • Hypertrophy of left ventricle involving intraventricular septum
    • Enlargement of one or both papillary muscles
    • Septal bulging into the LVOT:
      • Partial or complete LVOT outflow obstruction
    • Paradoxical motion of anterior leaflet of mitral valve (systolic anterior motion [SAM]):
      • Worsens LVOT obstruction
      • Causes MR in 30%
    • Exceptional RV involvement
  • Diagnosis of exclusion based on echo findings

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Figure 20-1. Comparison of Normal Heart and Heart with HCM
Graphic Jump Location

Normal heart (on left) compared with two types of hypertrophic cardiomyopathy (center and right). Note bulging of the septum into the LVOT. Reproduced from Fuster V, Walsh RA, Harrington RA. Hurst’s The Heart. Figure 33-11. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.

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Diagnosis

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  • Most common symptoms are dyspnea, angina, dizziness, and syncope:
    • May be late signs or nonapparent in older patients
  • Abnormal S4 heart sounds, systolic flow murmur
  • Misplaced apical impulse
  • Nonspecific EKG changes (atrial enlargement, LVH, inferolateral Q waves, PVCs)
  • Echo findings:
    • Pressure gradient through the LVOT:
      • This varies widely between patients
    • SAM of mitral valve:
      • Dynamic outflow obstruction
      • Due to following conditions:
        • Anterior position of the mitral valve in the LV
        • Altered LV geometry due to septal bulge (hypertrophy)
        • Chordal slack
        • Venturi forces in the outflow tract (drop in pressure because of narrowed channel attracts anterior leaflet of mitral valve)
      • Described as closure of LVOT during systole
    • Mitral regurgitation

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Treatment

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  • Medical:
    • Focused on HR control and negative inotropy:
      • Beta-blockers
      • Calcium channel blockers
    • Often works for nonsymptomatic patients
    • ICD implantation for avoidance of sudden cardiac death (SCD)
  • Surgical:
    • Surgical myomectomy
    • Ablative procedures:
      • Decrease in mass of the ventricular hypertrophy
      • May be combined with corrective procedures to change aberrant anatomical problems with mitral valve

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  • Rule out associated myopathy
  • Know the patients’ functional status and the disease progression (i.e., symptoms they have had ongoing)
  • ICD often present to prevent SCD (see chapter 19 on ICD) must be deactivated prior to surgery (interrogation by company representative, or magnet if not possible)
  • Premedicate as appropriate to avoid anxiety-related tachycardia

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Monitors

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  • Arterial line, depending on:
    • Severity of hypertrophic cardiomyopathy (HCM) (i.e., symptomatic vs. incidental finding)
    • Nature and invasiveness of surgical procedure
  • TEE (and practitioner able to interpret) available to diagnose cause of hemodynamic deterioration

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Hemodynamic Principles

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  • Avoid factors that worsen obstruction:
    • Tachycardia (sympathetic stimulation, vagolysis)
    • Positive inotropes
    • Peripheral vasodilators
    • Hypovolemia
  • Have immediately available:
    • Esmolol, diltiazem
    • Phenylephrine

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Induction

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  • Balanced technique:
    • Avoid induction agents that decrease afterload (e.g., propofol) or increase HR (e.g., ketamine):
      • Etomidate and/or midazolam ...

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