A graphical analysis of aspects contributing to the spreading of measurements of left ventricular function

The Simpson’s method is the standard technique to determine left ventricular (LV) ejection fraction (EF) on echocardiography. The large inter-observer variability of measuring LVEF is well documented but not fully understood. A graphical analysis was used to elaborate what contributes to the inter-observer difference. Forty-two cardiologists (32 male, 39 ± 7 years) evaluated the LVEF using the Simpson’s method on 15 different echocardiograms (2 and 4 chamber view (2CH/4CH)); the program did not show the result of EF to prevent a bias. End-diastolic (ED) and end-systolic (ES) frames were predefined ensuring measurement at the same time point of the cardiac cycles. After standardization of the LV contour, the differences of the individual contours compared to a reference contour were measured. Also, the spreading of lateral/medial mitral annulus contours and the apex were depicted. A significant spreading of LV-contours was seen with larger contours leading to higher EFs (p < 0.001). Experience did not influence the determination of LVEF. ED-volumes showed more spreading than ES-volumes ((3.6 mm (IQR: 2.6–4.0) vs. 3.4 mm (IQR: 2.8–3.8), p < 0.001). Also, the differences were larger for the 2CH compared to the 4CH (p < 0.001). Variability was significantly larger for lateral than septal wall (p < 0.001) as well as the anterior compared to the inferior wall (p < 0.001). There was a relevant scattering of the apex and medial/ lateral mitral annulus ring. There was a large variability of LV-volumes and LVEF as well as position of mitral valve ring and apex. There were global differences (apical 2CH or 4CH), regional aspects (LV walls) and temporal factors (ED vs. ES). Thus, multiple factors contributed to the large variability. Trial registration: The study was registered at “Netherlands Trial Register” (www.trialregister.nl; study number: NL5131).