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Author Gonzalo Romero (Reviewed by Rim Halaby and Yazan Daaboul)
Exam Type USMLE Step 1
Main Category Pathology
Sub Category Cardiology
Prompt A 21-year-old male college student suddenly loses consciousness and falls while playing football. The player is unresponsive to verbal or physical stimuli, and has an undetectable pulse. Despite CPR and resuscitation efforts, the patient dies. According to his family and friends, the patient has always been healthy and has been playing soccer since high school. Further history reveals that two of the patient's relatives also died the same way. Autopsy is obtained in order to determine the cause of death. Which of the following cardiac changes is most likely present in this patient?
Answer A Symmetric left ventricular hypertrophy
Answer A Explanation [[AnswerAExp::Symmetric left ventricular hypertrophy is characteristically present in patients with increased afterload, such as aortic stenosis or hypertension. This leads to the increased synthesis of actin and myosin, which are normally arranged in a "organized fashion". Ultimately, these patients develop diastolic dysfunction due to the inability of the heart to fill in with blood during diastole.]]
Answer B White appearance of the endocardium
Answer B Explanation [[AnswerBExp::A white appearance of the endocardium can be present in endocardial fibroelastosis, a rare restrictive cardiomyopathy present in young children less than 2 years of age. It is caused by excessive fibrosis of the endocardium that causes diastolic dysfunction.]]
Answer C Cardiomyocyte hypertrophy in an organized fashion
Answer C Explanation [[AnswerCExp::Cardiomyocyte hypertrophy in an organized fashion is found among patients with increased afterload such as aortic stenosis or hypertension.]]
Answer D Prominent ventricular septum hypertrophy
Answer D Explanation [[AnswerDExp::Prominent ventricular septum hypertrophy is a characteristic finding of hypertrophic cardiomyopathy.]]
Answer E Fibrotic thickening of the endocardium and the valves of the right side of the heart
Answer E Explanation [[AnswerEExp::Fibrotic thickening of the endocardium and the valves of the right side of the heart is the macroscopic description of an endocardium affected by a carcinoid syndrome due to chronic serotonin exposure, which causes fibrosis of the tricuspid and pulmonary valves. Carcinoid syndrome occurs when the carcinoid tumor metastasizes to the liver, thereby bypassing the first-pass metabolism of the liver. These patients present with diarrhea, wheezing, telangiectasias, and flushing of the skin.]]
Right Answer D
Explanation [[Explanation::This young athlete presents with sudden cardiac death during intense exercise due to ventricular arrhythmias, a typical clinical presentation of hypertrophic obstructive cardiomyopathy (HOCM). HOCM is a genetic disorder caused by a missense mutation that encodes sarcomere proteins of the heart. It is relatively common, occurring in approximately 1 of every 500 adults.
  • Macroscopically, the heart demonstrates hypertrophy more prominent in the ventricular septum, obstructing the outflow from the left ventricle. Additional complications of the observed hypertrophy include mitral regurgitation due to systolic anterior motion (SAM) of the mitral valve, systolic and diastolic dysfunction, myocardial ischemia, and fatal ventricular arrhythmias.
  • Histologically, there are hypertrophied cardiomyocytes in disarray that alter the conduction system and subsequently predispose to arrhythmias.

HOCM should be suspected based on physical exam findings and abnormal findings on echocardiogram or even ECG. On physical exam, a systolic ejection murmur is typically heard at the left sternal border. The intensity of the murmur characteristically increases as preload decreases. Decreasing preload may be performed by changing the patient's position from a seated or squatting position to a standing position. Ultrasound is the diagnostic test of choice, demonstrating asymmetric myocardial hypertrophy with septal thickness greater than the thickness of the free wall.

The mainstay of HOCM therapy includes symptomatic relief and prevention of occurrence of arrhythmias, which may be the cause of death in these patients. Although the risk of death is less than 1% per year, young athletes with HOCM are specifically at risk of developing ventricular arrhythmias and death.

Other members of the family should also be included in the management plan. Immediate family members should be requested to perform periodic ultrasound because hypertrophy may become evident as late as 60 - 70 years of age.
Educational Objective: Hypertrophic obstructive cardiomyopathy (HOCM) is a common cause of sudden death in young athletes during intense exercise. It is characterized by the presence of cardiac hypertrophy more prominent in the ventricular septum and presence of hypertrophied cardiomyocytes in disarray.
References: Nishimura, RA; Holmes, DR. Hypertrophic obstructive cardiomyopathy. N Engl J Med. 2004;350:1320-1327. First Aid 2014 page 290]]

Approved Yes
Keyword Cardiology, Pathology, Hypertrophic cardiomyopathy, HOCM, HCM, Ischemia, Sudden death, Cardiomyopathy
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