A 14-year-old boy is brought to the office for evaluation after his father experienced sudden cardiac arrest during a hiking trip. The boy has no symptoms or known chronic medical conditions. Blood pressure is 110/60 mm Hg and pulse is 75/min. Physical examination shows a supple neck with no jugular venous distension. The carotid pulse has a dual upstroke. There is strong apical impulse, and a faint midsystolic murmur is best heard at the cardiac apex and along the left sternal border. The lungs are clear to auscultation. Which of the following maneuvers is most likely to increase the murmur intensity in this patient?

Question

A 14-year-old boy is brought to the office for evaluation after his father experienced sudden cardiac arrest during a hiking trip.  The boy has no symptoms or known chronic medical conditions.  Blood pressure is 110/60 mm Hg and pulse is 75/min.  Physical examination shows a supple neck with no jugular venous distension.  The carotid pulse has a dual upstroke.  There is strong apical impulse, and a faint midsystolic murmur is best heard at the cardiac apex and along the left sternal border.  The lungs are clear to auscultation.  Which of the following maneuvers is most likely to increase the murmur intensity in this patient?

Quizplus · Accepted Answer

11ec25c8_d631_d6ff_bc81_0f4dca84e366_MD0003_00 This patient and his father, who experienced sudden cardiac arrest on a hiking trip, most likely have hypertrophic cardiomyopathy (HCM). HCM is an autosomal dominant inherited condition resulting from mutations in one or more of several genes that code for cardiac sarcomere proteins (eg, myosin-binding protein C, beta-myosin heavy chain). The mutations result in asymmetric hypertrophy of the intraventricular septum that can lead to dynamic left ventricular outflow tract (LVOT) obstruction. Patients can experience dyspnea, fatigue, chest pain, light-headedness, and syncope; sudden cardiac arrest can result from reduced cardiac output or ventricular arrhythmia. The murmur of HCM is caused by blood flow through the LVOT, typically recognized as a midsystolic or crescendo-decrescendo systolic murmur best heard at the left sternal border or cardiac apex. The murmur characteristically varies in intensity with changes in left ventricular (LV) blood volume. Maneuvers that decrease LV blood volume (eg, the reduced venous return that occurs with Valsalva strain phase or standing from a supine position) decrease LV size; this worsens the LVOT obstruction and increases the intensity of the murmur. This contrasts with the murmur of aortic stenosis, which increases in intensity with increased ventricular preload. worsens the LVOT obstruction (Choice A) Squatting increases LV blood volume via both increased venous return (due to compression of venous capacitance veins) and increased afterload (due to kinking of the iliac arteries and increased systemic vascular resistance), reducing the intensity of the HCM murmur. (Choices B and C) Venous return to the heart is increased by the assumption of a supine position from standing, and it is further increased by raising the legs while supine. These maneuvers increase LV blood volume and reduce the intensity of the HCM murmur. (Choice D) A sustained handgrip increases afterload to increase LV blood volume and reduce the intensity of the HCM murmur. Increased afterload has the same reducing effect on the murmur of aortic stenosis, but for a different reason; the pressure gradient across the aortic valve is reduced. Educational objective: The murmur of hypertrophic cardiomyopathy (HCM) increases in intensity with maneuvers that decrease left ventricular blood volume and worsen left ventricular outflow tract obstruction. These include Valsalva strain phase and standing from a supine position, both of which decrease venous return to the heart. Conversely, the murmur of HCM decreases in intensity with maneuvers that increase left ventricular blood volume via increased venous return and/or increased afterload (eg, squatting, sustained handgrip). References: Comparison of Valsalva manoeuvre and exercise in echocardiographic evaluation of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy. (http://www.ncbi.nlm.nih.gov/pubmed/20472917)

A 14-Year-Old Boy Is Brought to the Office for Evaluation