A 24-year-old man experiences syncope while shoveling snow. He regains consciousness within 1 minute. He has had some shortness of breath and chest pains recently, related primarily to exercise. He denies illicit drug use. His temperature is 37.2° C (98.9° F), blood pressure is 126/76 mm Hg, pulse is 76/min, and respirations are 14/min. Physical examination shows a well-built man in no apparent distress. Lungs are clear. A crescendo-decrescendo systolic murmur is heard along the left sternal border without carotid radiation. Chest x-ray is normal. Which of the following is the most likely cause of his syncopal episode?

Question

A 24-year-old man experiences syncope while shoveling snow.  He regains consciousness within 1 minute.  He has had some shortness of breath and chest pains recently, related primarily to exercise.  He denies illicit drug use.  His temperature is 37.2° C (98.9° F), blood pressure is 126/76 mm Hg, pulse is 76/min, and respirations are 14/min.  Physical examination shows a well-built man in no apparent distress.  Lungs are clear.  A crescendo-decrescendo systolic murmur is heard along the left sternal border without carotid radiation.  Chest x-ray is normal.  Which of the following is the most likely cause of his syncopal episode?

Quizplus · Accepted Answer

This patient's crescendo-decrescendo systolic murmur along the left sternal border without carotid radiation is the description of the murmur present in hypertrophic obstructive cardiomyopathy (HOCM), which is interventricular septal hypertrophy. Common symptoms of HOCM include syncope, dyspnea, and chest pain, all of which this patient has experienced. Syncope in HOCM is multifactorial. In large part it is due to outflow obstruction from the hypertrophied myocardium. However, syncope can also be secondary to arrhythmia, ischemia, and a ventricular baroreceptor response that inappropriately causes vasodilation. (Choice A) Atrioventricular conduction delay occurs when conduction through the AV node is slowed, typically due to medications such as β-blockers or ischemic heart disease. This typically results in bradycardia, but this patient's heart rate is within the normal range. (Choice C) Syncope can occur with aortic dissections, particularly those involving the ascending aorta. However, the primary complaint in patients with aortic dissection is chest pain, which this patient does not appear to have. Painless aortic dissection is rare. Most patients with aortic dissection are also older and hypertensive. (Choice D) Isolated aortic stenosis in a young adult without a familial syndrome would be unusual but is a cause of exercise-related syncope. The location of the murmur (right second intercostal space for aortic stenosis) and lack of right carotid radiation help to differentiate it from aortic stenosis. (Choice E) Mitral valve degeneration leading to regurgitation rarely causes syncope. In addition, mitral regurgitation typically causes a holosystolic murmur as opposed to the crescendo-decrescendo type murmur heard in this patient. Educational objective: Syncope in a young patient with a crescendo-decrescendo murmur at the lower left sternal border is most likely due to hypertrophic obstructive cardiomyopathy (HOCM). Syncope in HOCM is often multifactorial and can be due to outflow obstruction, arrhythmia, ischemia, and a ventricular baroreceptor response that inappropriately causes vasodilation. References: The diagnosis and treatment of hypertrophic cardiomyopathy (http://www.ncbi.nlm.nih.gov/pubmed/21505608)

A 24-Year-Old Man Experiences Syncope While Shoveling Snow