A 64-year-old man presents to the office with chest discomfort and mild shortness of breath that started one hour ago after an argument with his wife. He has a long history of hypertension and diabetes mellitus. His blood pressure is 180/100 mmHg and his heart rate is 100/min. An EKG taken in the emergency department shows no signs of acute ischemia. Cardiac auscultation in the left decubitus position on full expiration reveals a presystolic sound. Which of the following best explains this physical examination finding?

Question

A 64-year-old man presents to the office with chest discomfort and mild shortness of breath that started one hour ago after an argument with his wife.  He has a long history of hypertension and diabetes mellitus.  His blood pressure is 180/100 mmHg and his heart rate is 100/min.  An EKG taken in the emergency department shows no signs of acute ischemia.  Cardiac auscultation in the left decubitus position on full expiration reveals a presystolic sound.  Which of the following best explains this physical examination finding?

Quizplus · Accepted Answer

An S4 is an isolated presystolic (late diastolic) sound heard just prior to S1. An S4 is caused by left atrial contraction that forces atrial blood into a poorly compliant left ventricle (LV) that is nearly filled to capacity. When blood is forced into the ventricle by the atrium under these conditions it generates a large, rapid increase in LV pressure thereby producing a sound possibly resulting from rapid deceleration of the forced blood or from impact of the filling ventricle with the chest wall. LV hypertrophy and other causes of diastolic heart failure therefore favor generation of an S4 sound. This patient's LV hypertrophy is likely secondary to chronic hypertension. (Choice A) Papillary muscle dysfunction may cause incomplete closure of the atrioventricular valves resulting in a murmur audible during systole. (Choice C) An increase in LV preload is typically accommodated by stretching in a normally compliant ventricle and does not result in characteristic heart sounds. (Choice D) Aortic regurgitation causes a decrescendo early and mid-diastolic murmur. (Choice E) Mitral leaflet fusion and fibrosis may cause mitral stenosis resulting in a mid-diastolic murmur with possible late diastolic (pre-systolic) accentuation due to atrial contraction. Educational objective: An S4 sound is best heard near the cardiac apex at the point of maximal impulse with the patient in the left lateral decubitus position. It results from the atrial contraction, which forces blood into an LV that has reached its limit of compliance. Chronic hypertension causes left ventricular hypertrophy, which itself may promote the generation of an S4 sound.

A 64-Year-Old Man Presents to the Office with Chest Discomfort and Mild