Challenges With Left Ventricular Functional Parameters: The Pediatric Heart Network Normal Echocardiogram Database

Abstract

Background: The reliability of left ventricular (LV) systolic functional indices calculated from blinded echocardiographic measurements of LV size has not been tested in a large cohort of healthy children. The objective of this study was to estimate interobserver variability in standard measurements of LV size and systolic function in children with normal cardiac anatomy and qualitatively normal function.

Methods: The Pediatric Heart Network Normal Echocardiogram Database collected normal echocardiograms from healthy children ≤18 years old distributed equally by age, gender, and race. A core lab used two-dimensional echocardiograms to measure LV dimensions from which a separate data coordinating center calculated LV volumes and systolic functional indices. To evaluate interobserver variability, two independent expert pediatric echocardiographic observers remeasured LV dimensions on a subset of studies, while blinded to calculated volumes and functional indices.

Results: Of 3,215 subjects with measurable images, 552 (17%) had a calculated LV shortening fraction (SF) < 25% and/or LV ejection fraction (EF) < 50%; the subjects were significantly younger and smaller than those with normal values. When the core lab and independent observer measurements were compared, individual LV size parameter intraclass correlation coefficients were high (0.81-0.99), indicating high reproducibility. The intraclass correlation coefficients were lower for SF (0.24) and EF (0.56). Comparing reviewers, 40/56 (71%) of those with an abnormal SF and 36/104 (35%) of those with a normal SF based on core lab measurements were calculated as abnormal from at least one independent observer. In contrast, an abnormal EF was less commonly calculated from the independent observers' repeat measures; only 9/47 (19%) of those with an abnormal EF and 8/113 (7%) of those with a normal EF based on core lab measurements were calculated as abnormal by at least one independent observer.

Conclusions: Although blinded measurements of LV size show good reproducibility in healthy children, subsequently calculated LV functional indices reveal significant variability despite qualitatively normal systolic function. This suggests that, in clinical practice, abnormal SF/EF values may result in repeat measures of LV size to match the subjective assessment of function. Abnormal LV functional indices were more prevalent in younger, smaller children.

Keywords: Echocardiography; Ejection fraction; Left ventricle; Pediatric; Shortening fraction.

Figure 1.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for measurements of left ventricular end-diastolic dimension (A), end-systolic dimension (B), end-diastolic area (C), end-systolic area (D), end-diastolic length (E), and end-systolic length (F). For all measurements, there were excellent correlations between observers, with an intraclass correlation coefficient (ICC) >0.91 for all comparisons between all observers (ICC for each measurement displayed in the graphs).

Figure 1.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for measurements of left ventricular end-diastolic dimension (A), end-systolic dimension (B), end-diastolic area (C), end-systolic area (D), end-diastolic length (E), and end-systolic length (F). For all measurements, there were excellent correlations between observers, with an intraclass correlation coefficient (ICC) >0.91 for all comparisons between all observers (ICC for each measurement displayed in the graphs).

Figure 1.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for measurements of left ventricular end-diastolic dimension (A), end-systolic dimension (B), end-diastolic area (C), end-systolic area (D), end-diastolic length (E), and end-systolic length (F). For all measurements, there were excellent correlations between observers, with an intraclass correlation coefficient (ICC) >0.91 for all comparisons between all observers (ICC for each measurement displayed in the graphs).

Figure 1.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for measurements of left ventricular end-diastolic dimension (A), end-systolic dimension (B), end-diastolic area (C), end-systolic area (D), end-diastolic length (E), and end-systolic length (F). For all measurements, there were excellent correlations between observers, with an intraclass correlation coefficient (ICC) >0.91 for all comparisons between all observers (ICC for each measurement displayed in the graphs).

Figure 1.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for measurements of left ventricular end-diastolic dimension (A), end-systolic dimension (B), end-diastolic area (C), end-systolic area (D), end-diastolic length (E), and end-systolic length (F). For all measurements, there were excellent correlations between observers, with an intraclass correlation coefficient (ICC) >0.91 for all comparisons between all observers (ICC for each measurement displayed in the graphs).

Figure 1.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for measurements of left ventricular end-diastolic dimension (A), end-systolic dimension (B), end-diastolic area (C), end-systolic area (D), end-diastolic length (E), and end-systolic length (F). For all measurements, there were excellent correlations between observers, with an intraclass correlation coefficient (ICC) >0.91 for all comparisons between all observers (ICC for each measurement displayed in the graphs).

Figure 2.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for the calculated left ventricular shortening fraction (SF). There were poor correlations between the observers, with an intraclass correlation coefficient (ICC) for comparisons between all observers of 0.24. Abnormal values for SF (<25%) as calculated from core lab measurements are displayed as red plus signs, and normal values (>25%) are displayed as blue circles.

Figure 3.

Representative graphs of values obtained from the core lab (x-axis) and Observer 1 (y-axis) for the calculated left ventricular ejection fraction (EF). There were moderate correlations between the observers, with an intraclass correlation coefficient (ICC) for comparisons between all observers of 0.56. Abnormal values for EF (<50%) as calculated from core lab measurements are displayed as red plus signs, and normal values (>50%) are displayed as blue circles.

Figure 4.

Still frame images of the left ventricle from a short axis plane in a child with calculated abnormal LV shortening fraction, demonstrating caliper position in the measurement of the left ventricular end-diastolic dimension (A) and end-systolic dimension (B). The end-diastolic dimension of 27.9 mm and end-systolic dimension of 21.5 mm result in a calculated shortening faction of 23% (27.9-21.5/27.9) despite the qualitatively normal function shown in Video 1 from the same patient.

Figure 4.

Still frame images of the left ventricle from a short axis plane in a child with calculated abnormal LV shortening fraction, demonstrating caliper position in the measurement of the left ventricular end-diastolic dimension (A) and end-systolic dimension (B). The end-diastolic dimension of 27.9 mm and end-systolic dimension of 21.5 mm result in a calculated shortening faction of 23% (27.9-21.5/27.9) despite the qualitatively normal function shown in Video 1 from the same patient.