Cardiomyopathy, Hypertrophic

Relatively common inherited disorder; 0.2% or 1 in 500 Americans are affected. It is equally distributed between males and females and has no racial group predominance. The median age of clinical manifestation is 35 years, but it can manifest in any age.

The clinical presentation is variable, reflecting a diverse genetic background. Pts may be totally asymptomatic or present with MI, CHF, arrhythmias, or even sudden death. HCM is not an infrequent cause of SCD in young athletes.

Pts with the disorder may be asymptomatic (20–25%) or undiagnosed at the time of anesthetic. Anesthesia may “unmask” HCM.

Dynamic LV outflow obstruction (either at rest or provoked) is present in approx 60% of pts with HCM, which is a risk of hemodynamic instability.

Risk for heart failure and pulm edema from impaired relaxation and diastolic dysfunction from a hypertrophic and noncompliant LV.

Risk for myocardial ischemia and injury, even in the absence of obstructive CAD, due to increased myocardial O ₂ demand (LVH, high intraventricular pressure) and limited supply (impaired coronary reserve, due to dysfunction of the coronary microvasculature).

Supraventricular (atrial fibrillation) and ventricular dysrhythmias.

Factors that aggravate or trigger dynamic outflow obstruction can cause hemodynamic compromise, such as decreased preload and afterload, decreased end diastolic volume, increased sympathetic activation (from pain, surgical stimulation, medications), increased LV contractility, and tachycardia.

Myocardial ischemia (even with “normal” coronary angiogram or radionuclide imaging).

Diastolic dysfunction; heart failure difficult to control with traditional diuresis (caution with volume depletion).

Arrhythmias: Supraventricular and ventricular dysrhythmias may cause hemodynamic instability, increase the risk of embolic stroke (AFIB), and cause shortness of breath or CHF (diastolic dysfunction).

Pts with HCM who undergo noncardiac surgery bear a higher risk for periop MI, death (4.2%), and higher incidence of periop complications.

Genetic disease with autosomal dominant inheritance and extremely heterogeneous genotype. Over 1400 mutations have been identified in at least 11 genes. This is most likely the reason for the extremely variable genetic expression or phenotype. Mutations that encode for the myosin heavy chain (MYH7) and myosin-binding protein C3 account for 70%–80% of sarcomeric mutations. Genetic testing is recommended for pts and their first-degree relatives.