Functional measurements based on feature tracking of cine magnetic resonance images identify left ventricular segments with myocardial scar

Abstract

Background: The aim of the study was to perform a feature tracking analysis on cine magnetic resonance (MR) images to elucidate if functional measurements of the motion of the left ventricular wall may detect scar defined with gadolinium enhanced MR.Myocardial contraction can be measured in terms of the velocity, displacement and local deformation (strain) of a particular myocardial segment. Contraction of the myocardial wall will be reduced in the presence of scar and as a consequence of reduced myocardial blood flow.

Methods: Thirty patients (3 women and 27 men) were selected based on the presence or absence of extensive scar in the anteroseptal area of the left ventricle. The patients were investigated in stable clinical condition, 4-8 weeks post ST-elevation myocardial infarction treated with percutaneous coronary intervention. Seventeen had a scar area >75% in at least one anteroseptal segment (scar) and thirteen had scar area <1% (non-scar). Velocity, displacement and strain were calculated in the longitudinal direction, tangential to the endocardial outline, and in the radial direction, perpendicular to the tangent.

Results: In the scar patients, segments with scar showed lower functional measurements than remote segments. Radial measurements of velocity, displacement and strain performed better in terms of receiver-operator-characteristic curves (ROC) than the corresponding longitudinal measurements. The best area-under-curve was for radial strain, 0.89, where a cut-off value of 38.8% had 80% sensitivity and 86% specificity for the detection of a segment with scar area >50%. As a percentage of the mean, intraobserver variability was 16-14-26% for radial measurements of displacement-velocity-strain and corresponding interobserver variability was 13-12-18%.

Conclusion: Feature tracking analysis of cine-MR displays velocity, displacement and strain in the radial and longitudinal direction and may be used for the detection of transmural scar. The accuracy and repeatability of the radial functional measurements is satisfactory and global measures agree.

Figure 1

Transmurality of scar calculated from LGE image in the 2-chamber view. Scar is 100% transmural along the middle and apical part of the anterior wall extending to the apical part of the inferior wall. Calculation performed with the Segment software.

Figure 2

Feature tracking of patient with extensive scar as shown in Figure 1. Upper left shows vector arrows of late systolic velocity tracing, 190 ms after QRS (green). Upper right shows radial strain tracing of the entire cardiac cycle. Blue represents the apex showing very low strain values; red is the normal posterior wall. Lower right displays longitudinal traces from the same locations, with postsystolic strain in the apex. Lower left is volume curve based on single plane Simpson (red) and emptying velocity (dV/dt), blue tracing.

Figure 3

Measurement window of feature tracking software. Middle figures show graphical display of 6 segments, three anterior and three inferoposterior. Right upper panel shows radial strain tracings from the six segments. Lower right panel depicts the corresponding longitudinal strain values. Velocity and displacement can be selected for alternative presentation. Left blue box shows peak values and time to peak for corresponding segments.

Figure 4

Functional measures vs. location, non-scar patients. Left sided panels show radial displacement (upper), velocity (mid) and strain (lower), from three different segment levels, apex-mid-base. Right sided panels show the corresponding longitudinal values. o = denotes statistically significant difference (p < 0.05) compared to basal x = denotes statistically significant difference (p < 0.05) compared to nearest left value

Figure 5

Functional measures vs. transmurality, all patients (Ctrl = non-scar). Left-sided panels show radial displacement (upper), velocity (mid) and strain (lower) in segments with various degree of transmurality. Right-sided panels show the corresponding longitudinal values. o = denotes statistically significant difference (p < 0.05) compared to controls (Ctrl) x = denotes statistically significant difference (p < 0.05) compared to nearest left value

Figure 6

ROC curves for the functional measures vs. >50% transmurality. The composite of the radial measures strain-displacement-velocity shows only marginally larger AUC than radial strain alone. ROC curves for the detection of 50% segmental scar using 1 = Composite, 2 = Radial strain, 3 = Radial displacement, 4 = Radial velocity, 5 = Longitudinal strain, 6 = Longitudinal velocity, 7 = Longitudinal displacement

Figure 7

Correlation between global functional measurements and MR-determined LVEF. Highest correlation (r = 0.84, 0.84 and 0.79) was between radial displacement, radial velocity and longitudinal strain vs. ejection fraction determined from a stack of shortaxis cine MRI.