Question 31

Question:

A 19-year-old male comes to your office with complaints of increasing shortness of breath while preparing for the upcoming basketball season. Upon further questioning, it is revealed that his father would suddenly lose and regain consciousness in his youth while participating in sports. On physical examination, you perceive a systolic murmur on the left sternal border that is accompanied by an S4 gallop. His EKG is suggestive of left ventricular hypertrophy. Which of the following will most likely decrease the murmur that is heard upon auscultation?

Correct Answer: D.  increased preload, increased afterload

The patient in this case has hypertrophic obstructive cardiomyopathy (HOCM), which has an underlying pathology of septal hypertrophy and systolic anterior motion of the mitral valve, both resulting in left ventricular outflow obstruction. He presents with the most common complaint which is dyspnea secondary to decreased diastolic function of the heart (less common presentations of HOCM are syncope and sudden death). There can be a family history of HOCM, which has an autosomal dominant mode of inheritance. A systolic murmur on the left sternal border and an S4 gallop are characteristic findings for HOCM. Remember that an S4 gallop is indicative of a non-compliant stiff left ventricle and is usually found when there is left ventricular hypertrophy (which the patient has reflected on his EKG).

Because the underlying result of the pathology of HOCM is outflow obstruction, the murmur decreases (softens) when the left ventricular chamber size is larger and more full. This happens when there is an increased preload (i.e. squatting and leg raising) and an increased afterload (i.e. handgrip).

The murmur will increase (become louder) when there is a decrease in afterload (i.e. amyl nitrate) or if there is a decrease in preload (i.e. Valsalva or standing).