Cardiovascular magnetic resonance feature-tracking assessment of myocardial mechanics: Intervendor agreement and considerations regarding reproducibility

Abstract

Aim: To assess intervendor agreement of cardiovascular magnetic resonance feature tracking (CMR-FT) and to study the impact of repeated measures on reproducibility.

Materials and methods: Ten healthy volunteers underwent cine imaging in short-axis orientation at rest and with dobutamine stimulation (10 and 20 μg/kg/min). All images were analysed three times using two types of software (TomTec, Unterschleissheim, Germany and Circle, cvi(42), Calgary, Canada) to assess global left ventricular circumferential (Ecc) and radial (Err) strains and torsion. Differences in intra- and interobserver variability within and between software types were assessed based on single and averaged measurements (two and three repetitions with subsequent averaging of results, respectively) as determined by Bland-Altman analysis, intraclass correlation coefficients (ICC), and coefficient of variation (CoV).

Results: Myocardial strains and torsion significantly increased on dobutamine stimulation with both types of software (p<0.05). Resting Ecc and torsion as well as Ecc values during dobutamine stimulation were lower measured with Circle (p<0.05). Intra- and interobserver variability between software types was lowest for Ecc (ICC 0.81 [0.63-0.91], 0.87 [0.72-0.94] and CoV 12.47% and 14.3%, respectively) irrespective of the number of analysis repetitions. Err and torsion showed higher variability that markedly improved for torsion with repeated analyses and to a lesser extent for Err. On an intravendor level TomTec showed better reproducibility for Ecc and torsion and Circle for Err.

Conclusions: CMR-FT strain and torsion measurements are subject to considerable intervendor variability, which can be reduced using three analysis repetitions. For both vendors, Ecc qualifies as the most robust parameter with the best agreement, albeit lower Ecc values obtained using Circle, and warrants further investigation of incremental clinical merit.

Figure 1

Example of the derivation of LV Ecc curves, using the two commercially available CMR-FT software types.

Figure 2

Changes in the Ecc and Err LV strain and myocardial torsion during dobutamine stimulation: The figure shows changes in myocardial torsion (left panel), Ecc (middle panel), and Err (right panel) at rest and with dobutamine stimulation (10 and 20 μg/kg/min).

Figure 3

Intervendor agreement of global strain and myocardial torsion as determined by feature tracking. Bland–Altman plots with limits of agreement (95% confidence intervals) demonstrate the intervendor reproducibility of CMR-FT-derived myocardial torsion, global left ventricular Ecc and global left ventricular Err both on the intra-observer and interobserver level. The data shown is based on the measurements at rest and with dobutamine stress. Reproducibility is shown for averaged results based on three repeated measurements (R3).

Figure 4

Intervendor agreement of global Err and myocardial torsion as assessed by CoV and ICC. The graphs show the CoV in percent and the ICC on an intra-observer and interobserver level for global left ventricular Ecc, global left ventricular Err, and myocardial torsion. The change in reproducibility (based on CoV and ICC) is shown when deriving the results from a single analysis seen on the left of each graph (‘1 repetition’), averaging of two analyses ‘2 repetitions’ (middle of each graph) and averaging three analysis runs (‘3 repetitions’ right of each graph). The reproducibility results presented in theses graphs are based on strain and torsion values derived at rest and during dobutamine stimulation.