A 27-year-old professional snowboarder experienced a syncopal episode while training on a closed ski slope at Snowbird. The “Dude” (as he likes to call himself) was found at the scene in ventricular tachycardia and was successfully cardioverted by the emergency medical response team. On questioning, he admitted to experiencing some vague chest discomfort and shortness of breath over the past several months that he attributed to the altitude (>8,000 ft) and some “vigorous aprés ski celebrating.” Following some strong encouragement from his adoring entourage, he agreed to forego the rest of the day’s snowboarding to visit the local hospital. Medical evaluation demonstrated the presence of hypertrophic obstructive cardiomyopathy (HCM).

Now, adorned with his orange lens shades, he presents to your preoperative clinic for anesthesia consult prior to surgical septal myomectomy. Review of his past medical and surgical history is unremarkable. Family history is significant for a paternal uncle and grandfather with sudden death in their twenties. He takes atenolol 100 mg each morning and has no allergies. Vital signs are blood pressure 110/62 mm Hg, heart rate regular at 64/minute, and 100% oxygen saturation on room air. Physical exam revealed a noticeable double apical impulse and III/VI systolic ejection murmur at the left sternal border with radiation to the sternal notch, but not to the common carotid arteries. The murmur intensifies with upright posture, Valsalva maneuver, and squatting. The electrocardiogram showed normal sinus rhythm with electrical criteria for ventricular hypertrophy and diffuse depression of the ST segments. Chest film revealed a minimally increased cardiac silhouette. Echocardiography revealed ventricular hypertrophy with a marked asymmetrically enlarged upper interventricular septum. The mean gradient across the left ventricular outflow tract (LVOT) was calculated to be 55 mm Hg. The mitral valve showed signs of systolic anterior motion (SAM) and mild to moderate mitral insufficiency. Cardiac catheterization revealed normal coronary anatomy and confirmed the LVOT gradient. He wants to know how soon he could be back on the slopes.

HCM (formerly known as HOCM or idiopathic hypertrophic subaortic stenosis [IHSS]) is increasingly recognized as a relatively common (i.e.,
estimated incidence of approximately 1/500) and underdiagnosed congenital cardiac abnormality. Although the disease is known to be a frequent cause of sudden cardiac death in young people, the majority of affected patients is minimally symptomatic and has a normal lifespan.

HCM is an autosomal disease with variable penetrance associated with mutations in the sarcomeric proteins. The main pathological mechanisms include hypertrophy, obstruction, diastolic dysfunction, and arrhythmias. Asymmetric hypertrophy is the trademark of the disease, with the interventricular septum being the most common area of involvement. Upper septal hypertrophy creates an area of narrowing and increases the velocity of the blood in the LVOT, which in turn leads to a Venturi effect and SAM of the mitral valve. The end result of this physiological pattern is a characteristic dynamic obstruction in mid to late systole. SAM resulting in significant mitral regurgitation will decrease forward cardiac flow. Increased inotropism, chronotropism, and hypovolemia can accentuate the dynamic obstruction in HCM patients. The diastolic dysfunction associated with HCM translates into decreased ventricular compliance and leads to requirements for higher cardiac filling pressures and a dependence on the atrial contribution for adequate cardiac output. Any type of arrhythmia can be associated with HCM, particularly atrial fibrillation (i.e., there is an incidence of up to 25%) and malignant ventricular arrhythmias; thus, the risk of sudden cardiac death becomes apparent.