Hensley's Practical Approach to Cardiothoracic Anesthesia

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III. Cardiac Anesthesia

FIGURE 16.3 Intraoperative transesophageal echocardiography. (A) Systolic anterior motion (SAM) of the mitral valve into left ventricular outflow tract causing mitral insufficiency. (B) SAM and severe mitral regurgitation with posteriorly directed jet. (C) High-velocity, late peaking, “dagger-shaped” continuous-wave Doppler signal demonstrating an ob struction of left ventricular outflow tract. (D) Postoperative result demonstrating normal laminal flow in left ventricular outflow tract and interventricular septum post myectomy (yellow arrows).

The familial form comprises ∼ 60%-80% of the HCM population, but patients who develop HCM sporadically with de novo mutations in genes have similar characteristics as those with the familial form of HCM. 11 Genetic testing is available clinically; however, only approximately 34% of patients with HCM might have an identifiable gene mutation. In addition to finding pathogenic muta tions, a significant proportion of patients will have a variant of uncertain significance. 12 The relationship between a specific mutation and clinical outcome or prognosis has yet to be established. 13 Thus, the clinical use of genetic testing is confined mainly to screening at-risk phenotype-negative family members of a patient with definitive HCM. CLINICAL PEARL Phenotypical features of HCM and severity of hypertrophy cannot be inferred from the genotype. Genetic testing is available clinically; however, only about one-third of patients with HCM will have an identifiable gene mutation. The disorganized whirling of muscle fibers and myocardial disarray are characteristics, but not specific, of HCM. Late gadolinium enhancement suggesting myocardial fibrosis on cardiac MRI has been associated with an increased risk of sudden cardiac death.

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