Hypertrophic cardiomyopathy

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Hypertrophic cardiomyopathy

Cardiovascular system

Cardiac tumors

Cardiac tumors




Hypertrophic cardiomyopathy


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USMLE® Step 1 questions

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High Yield Notes

8 pages


Hypertrophic cardiomyopathy

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USMLE® Step 1 style questions USMLE

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A 15-year-old boy comes to the clinic because of progressively worsening dyspnea upon exertion and chest pain for the past 6 months. He has not had prior episodes of syncope, but he does describe moments in which he felt lightheaded and weak which improved with rest. Temperature is 37.2°C (98.9°F), pulse is 65/min, respirations are 17/min, and blood pressure is 110/80 mm Hg. Physical examination shows an athletic young man in mild distress. Cardiac examination shows a 4/6 systolic crescendo-decrescendo murmur best heard between the apex and the left sternal border on auscultation. Palpation of the precordium leads to a sustained impulse best felt at the apex. Which of the following will most likely decrease the intensity of the murmur heard on the physical examination?  

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Autosomal dominant disorders

hypertrophic cardiomyopathy p. 317

β -blockers p. 247

hypertrophic cardiomyopathy p. 317

Calcium channel blockers p. 325

hypertrophic cardiomyopathy p. 317

Friedreich ataxia p. 549

hypertrophic cardiomyopathy p. 317

Hypertrophic cardiomyopathy p. 317

Pompe disease p. 85

systolic murmur in p. 297


Cardiomyopathy means “heart muscle disease,” so cardiomyopathy is a broad term used to describe a variety of issues that result from disease of the myocardium, or heart muscle.

When cardiomyopathy develops as a way to compensate for some other underlying disease, like hypertension or valve diseases, it’s called secondary cardiomyopathy; when it develops all by itself, it’s called primary cardiomyopathy.

Now, hypertrophic cardiomyopathy is when the walls get thick, heavy, and hypercontractile; essentially, the muscles grow a lot larger because new sarcomeres are being added parallel to existing ones.

Usually, the left ventricle is affected, and in most cases, this muscle growth is asymmetrical, meaning that the interventricular septum grows larger relative to the free wall.

These larger muscles do two things: the walls take up more room, so less blood is able to fill the ventricle; and they become more stiff and less compliant, so they can’t stretch out as much, again, leading to less filling. When the ventricles don’t fill as much, they don’t pump out as much blood, and so stroke volume goes down. Thus, the heart can fail to pump enough blood to the body; this is called heart failure. Because this is due to a dysfunction in filling, which happens during diastole, this is a type of diastolic heart failure.

In some patients, the muscle growth of the interventricular septum essentially gets in the way of the left ventricular outflow tract during systole, or ventricular contraction. This increases blood velocity through the smaller opening, and pulls the anterior leaflet of the mitral valve toward the septum. This is called the venturi effect, which further obstructs the left ventricular outflow tract. For this reason, hypertrophic cardiomyopathy is sometimes called hypertrophic obstructive cardiomyopathy.


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  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "Hypertrophic Cardiomyopathy" Anesthesia & Analgesia (2015)
  5. "Hypertrophic cardiomyopathy: Part 1 - Introduction, pathology and pathophysiology" Annals of Cardiac Anaesthesia (2014)
  6. "Asymptomatic Hypertrophic Cardiomyopathy" Veterinary Clinics of North America: Small Animal Practice (2017)

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