Which imaging parameter most directly reflects left ventricular filling and preload?

• A. Left atrial size
• B. LV end-diastolic volume
• C. Cardiac output
• D. E/e' ratio

Answer: (B)

Left ventricular preload is the amount of blood filling the ventricle at the end of diastole, i.e., the end-diastolic volume. Imaging that directly measures this end-diastolic blood volume best reflects preload, so left ventricular end-diastolic volume is the most direct indicator of LV filling. Left atrial size tends to change with chronic elevations in filling pressures and remodeling, so it’s not a snapshot of current filling. The E/e' ratio estimates LV filling pressures and diastolic function rather than the actual volume in the ventricle. Cardiac output depends on preload, afterload, and contractility, but it isn’t a direct measure of preload itself.