A 39-year-old man comes to the office due to increasing fatigue for the past 2 weeks. The patient reports no prior medical conditions, although he recently had a self-limiting upper respiratory illness. He does not use tobacco, alcohol, or illicit drugs and has not traveled recently. Temperature is 37.2 C (99 F), blood pressure is 116/66 mm Hg, pulse is 100/min, and respirations are 20/min. Physical examination reveals lung crackles. Echocardiography shows no valvular abnormalities and the following parameters: Based on the observed findings, which of the following is most accurate about this patient?

Question

A 39-year-old man comes to the office due to increasing fatigue for the past 2 weeks.  The patient reports no prior medical conditions, although he recently had a self-limiting upper respiratory illness.  He does not use tobacco, alcohol, or illicit drugs and has not traveled recently.  Temperature is 37.2 C (99 F), blood pressure is 116/66 mm Hg, pulse is 100/min, and respirations are 20/min.  Physical examination reveals lung crackles.  Echocardiography shows no valvular abnormalities and the following parameters:  Based on the observed findings, which of the following is most accurate about this patient?

Quizplus · Accepted Answer

11ec160b_3c83_1e75_9249_9db1472f5484_MD0001_00 Left ventricular stroke volume is the absolute volume of blood ejected from the left ventricle with each contraction. It is calculated by subtracting the volume of blood in the left ventricle at the end of contraction, the left ventricular end-systolic volume, from the volume of blood in the left ventricle at the beginning of contraction, the left ventricular end-diastolic volume (LVEDV). This patient's stroke volume is 50 mL (125 mL − 75 mL), which is lower than the expected normal value of approximately 70 mL. Ejection fraction, the relative volume of blood ejected from the left ventricle with each contraction, is calculated by dividing stroke volume by LVEDV. In this patient, the ejection fraction is 0.4 (50 mL / 125 mL). The fraction is typically multiplied by 100 and expressed as a percentage; therefore, this patient's left ventricular ejection fraction is 40% (0.4 × 100), which is lower than the expected normal value of ≥50%. Cardiac output, the volume of blood ejected into the aorta per unit time, is estimated by multiplying stroke volume by heart rate. This patient's cardiac output is 5 L/min (50 mL × 100/min), which is normal. Although it is not pertinent to this patient, this equation overestimates cardiac output in the setting of mitral regurgitation because a portion of the stroke volume flows backward into the left atrium with each contraction. This patient's presentation is consistent with left ventricular systolic dysfunction leading to heart failure with reduced ejection fraction. He has only mild symptoms at present because the low stroke volume is being compensated by an elevated heart rate to maintain cardiac output; however, further decompensation with reduced cardiac output is likely over time. Educational objective: Stroke volume is the absolute volume of blood ejected from the left ventricle with each contraction and is calculated by subtracting left ventricular end-systolic volume from left ventricular end-diastolic volume (LVEDV). Ejection fraction is the relative volume of blood ejected from the left ventricle with each contraction; it is calculated by dividing stroke volume by LVEDV. Cardiac output, the volume of blood ejected into the aorta per unit time, is estimated by multiplying stroke volume by heart rate.

A 39-Year-Old Man Comes to the Office Due to Increasing