Estimation of hydraulic forces that contribute to left ventricular filling assessed by echocardiography is not directly comparable to magnetic resonance imaging in children with atrial septal defects. (RF_FR_420)

Background: Hydraulic forces of the heart contribute to left ventricular filling and can be estimated using cardiac magnetic resonance (CMR) [1]. The difference in cross-sectional area between the smaller left atrium and the larger left ventricle, the atrioventricular area difference (AVAD), facilitates the movement of the atrioventricular plane towards the left atrium. Transthoracic echocardiography (TTE) in adult patients with heart failure associates reduction of AVAD and hydraulic force with adverse events [2]. In children, it is unknown how estimates of hydraulic force by TTE compares to CMR. Using TTE validated by CMR could simplify clinical application as TTE is widely available and well accepted, even by small children without the need for sedation.

Aim: To compare TTE to CMR for measurement of hydraulic forces by means of AVAD indexed to height in healthy children and in children with atrial septal defects.

Methods:

Methods: Forty-two children (17 controls, 25 with atrial septal defect) were included. Seventeen underwent TTE and CMR once, and 17 underwent TTE and CMR both prior to and up to 12 months after atrial septal defect closure. Indexed AVAD was derived from CMR short-axis stacks as previously described [1, 3]. For AVAD by TTE, the maximum diameter of the left atrium and left ventricle in diastole were measured in parasternal long-axis views. Both acquisitions were performed on the same day in all subjects. Repeated TTE measurements were performed to assess test-retest variability calculated as the intraclass correlation coefficient (ICC). Data are presented as median [IQR]. Bland-Altman analysis assessed agreement, and Wilcoxon’s test assessed  differences, with p< 0.05 considered to show statistically significant differences.

Results:

Results: A total of 51 paired TTE and CMR measurements were available for analyses. Table 1 shows participant characteristics. Hydraulic forces were directed towards the left ventricle in all cases, i.e. aiding diastolic filling. Indexed AVAD by TTE was smaller than by CMR (6.0 [5.3–7.1] vs 8.0 [6.2–10.2] cm²/m; p< 0.001). Repeated measurements of indexed AVAD by TTE showed ICC=0.977 (95% CI: 0.958–0.988). Figure 1 shows agreement between TTE and CMR with a systematic bias.

Conclusion:

Conclusions: Hydraulic forces by means of measuring indexed AVAD using TTE and CMR in children is feasible but not interchangeable with the TTE method generally underestimating true values as defined by CMR.

Figure 1: Bland-Altman comparison showing agreement between TTE and CMR to estimate hydraulic forces by means of atrioventricular area difference indexed to height (AVADi) in children. Bias was -0.14 cm2/m with the lower 95 % limit of agreement -4.15 cm2/m and upper 95 % limit of agreement +4.44 cm2/m.
B-A plot AVADi CMR vs TTE 11 Sep 2024.pdf