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Based on the graph of the left ventricular pressure–volume loop, which of the following BEST represents this hypothetical patient’s calculated ejection fraction?
Answer: (C) 58%. Read the discussion below.
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The Frank–Starling relationship describes the intrinsic property of myocardial cells to exhibit enhanced performance in response to greater stretch or tension. In the intact heart, pressure–volume loops provide graphic displays of the relationship between left ventricular pressure and volume (Figure 1).
Figure 1. Pressure–volume loop. (A) indicates aortic valve closure, (B) indicates the left ventricular end-systolic volume (mL), (C) indicates the left ventricular end-diastolic volume (mL), and (D) indicates the opening of the aortic valve. © 2021 American Society of Anesthesiologists.
The most commonly used index of ventricular function is the ejection fraction (EF). EF can be determined by a number of invasive and noninvasive mechanisms. On the pressure–volume loop presented here, point B represents left ventricular end-systolic volume and point C represents left ventricular end-diastolic volume. The difference between the two represents the stroke volume.
Using the pressure–volume loop presented, EF would be calculated as follows:
Ejection fraction % = (LVEDV – LVESV) / (LVEDV) × 100%
Therefore, ejection fraction % = (120 mL – 50 mL) / (120 mL) × 100% = 58%
Where:
LVEDV = left ventricular end-diastolic volume
LVESV = left ventricular end-systolic volume
(LVEDV – LVESV) = stroke volume
REFERENCE
1. Gropper MA, Cohen NH, Eriksson LI, Fleisher LA, Leslie K, Wiener-Kronish JP, eds. Miller’s Anesthesia. 9th ed. Elsevier; 2020:384.
