A 15-year-old boy is found to have a murmur during a routine sports physical examination. He has no complaints and has excellent exercise capacity. His maternal uncle died while swimming at age 24. The patient's blood pressure is 122/70 mm Hg and pulse is 63/min. A faint midsystolic murmur is heard along the lower left sternal border when the patient is supine. When the patient is asked to stand, a 3/6 systolic crescendo-decrescendo murmur is heard in the same location. Which of the following is the most likely mitral valve abnormality in this patient?

Question

A 15-year-old boy is found to have a murmur during a routine sports physical examination.  He has no complaints and has excellent exercise capacity.  His maternal uncle died while swimming at age 24.  The patient's blood pressure is 122/70 mm Hg and pulse is 63/min.  A faint midsystolic murmur is heard along the lower left sternal border when the patient is supine.  When the patient is asked to stand, a 3/6 systolic crescendo-decrescendo murmur is heard in the same location.  Which of the following is the most likely mitral valve abnormality in this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d632_7340_bc81_03020c9e4f5a_MD0003_00 This patient's presentation is consistent with hypertrophic cardiomyopathy (HCM), an autosomal dominant condition most commonly due to sarcomere gene mutations. Many patients with HCM are asymptomatic and are diagnosed with an abnormal murmur or ECG during routine evaluation. The clinical manifestations of HCM include: Exertional dyspnea, chest pain, fatigue, palpitations, presyncope or syncope Harsh crescendo-decrescendo systolic murmur with change in intensity on physiologic maneuvers (Table) Patients with HCM have increased left ventricular wall thickness, most commonly noted in the basal anterior septum (asymmetric septal hypertrophy). Some patients have systolic anterior motion of the mitral valve, leading to anterior motion of mitral valve leaflets toward the interventricular septum. Contact between the mitral valve and the thickened septum during systole leads to left ventricular outflow tract obstruction (LVOT) and is responsible for the harsh systolic murmur best heard at the apex and left lower sternal border. Abrupt standing from a sitting position decreases venous return and enhances LVOT, resulting in an increase in the intensity of the murmur. systolic anterior motion (Unlike HCM, hypertrophy due to hypertension or other cardiovascular heart diseases [eg, valvular, ischemic] is no longer considered a form of cardiomyopathy.) (Choice B) Dilation of the mitral valve annulus is seen in patients with dilated cardiomyopathy or ischemic cardiomyopathy and leads to mitral regurgitation (MR) due to inadequate valve coaptation. The murmur of MR is a holosystolic murmur that is best heard at the cardiac apex with radiation to the left axilla and decreases in intensity with abrupt standing from a supine position. (Choice C) Mitral annulus calcification is an age-related calcification of the fibrous annulus of the mitral valve. It is usually asymptomatic; however, it can cause mitral stenosis (diastolic rumble best heard at the apex) in patients with extensive calcification. (Choice D) Mitral valve prolapse occurs due to myxomatous degeneration of the mitral valve leaflets and/or chordae tendineae. Cardiac auscultation shows a nonejection click along with a mid-to-late systolic murmur of MR. (Choice E) Rupture of the chordae tendineae can occur in patients with mitral valve prolapse, infective endocarditis, trauma, or myocardial infarction. This leads to MR with a mid-to-late systolic murmur best heard at the cardiac apex. Educational objective: The primary mitral valve abnormality in patients with hypertrophic cardiomyopathy is the presence of systolic anterior motion of the mitral valve, leading to anterior motion of mitral valve leaflets toward the interventricular septum. Contact between the mitral valve and the thickened septum during systole leads to left ventricular outflow tract obstruction. References: The mitral valve in obstructive hypertrophic cardiomyopathy: a test in context. (http://www.ncbi.nlm.nih.gov/pubmed/27081025) Mitral valve and papillary muscle abnormalities in hypertrophic obstructive cardiomyopathy. (http://www.ncbi.nlm.nih.gov/pubmed/26192489)

A 15-Year-Old Boy Is Found to Have a Murmur During