Cardiovascular magnetic resonance myocardial feature tracking detects quantitative wall motion during dobutamine stress

Abstract

Background: Dobutamine stress cardiovascular magnetic resonance (DS-CMR) is an established tool to assess hibernating myocardium and ischemia. Analysis is typically based on visual assessment with considerable operator dependency. CMR myocardial feature tracking (CMR-FT) is a recently introduced technique for tissue voxel motion tracking on standard steady-state free precession (SSFP) images to derive circumferential and radial myocardial mechanics.We sought to determine the feasibility and reproducibility of CMR-FT for quantitative wall motion assessment during intermediate dose DS-CMR.

Methods: 10 healthy subjects were studied at 1.5 Tesla. Myocardial strain parameters were derived from SSFP cine images using dedicated CMR-FT software (Diogenes MRI prototype; Tomtec; Germany). Right ventricular (RV) and left ventricular (LV) longitudinal strain (EllRV and EllLV) and LV long-axis radial strain (ErrLAX) were derived from a 4-chamber view at rest. LV short-axis circumferential strain (EccSAX) and ErrSAX; LV ejection fraction (EF) and volumes were analyzed at rest and during dobutamine stress (10 and 20 μg · kg⁻¹· min⁻¹).

Results: In all volunteers strain parameters could be derived from the SSFP images at rest and stress. EccSAX values showed significantly increased contraction with DSMR (rest: -24.1 ± 6.7; 10 μg: -32.7 ± 11.4; 20 μg: -39.2 ± 15.2; p < 0.05). ErrSAX increased significantly with dobutamine (rest: 19.6 ± 14.6; 10 μg: 31.8 ± 20.9; 20 μg: 42.4 ± 25.5; p < 0.05). In parallel with these changes; EF increased significantly with dobutamine (rest: 56.9 ± 4.4%; 10 μg: 70.7 ± 8.1; 20 μg: 76.8 ± 4.6; p < 0.05). Observer variability was best for LV circumferential strain (EccSAX ) and worst for RV longitudinal strain (EllRV) as determined by 95% confidence intervals of the difference.

Conclusions: CMR-FT reliably detects quantitative wall motion and strain derived from SSFP cine imaging that corresponds to inotropic stimulation. The current implementation may need improvement to reduce observer-induced variance. Within a given CMR lab; this novel technique holds promise of easy and fast quantification of wall mechanics and strain.

Figure 1

Tracking in Short-Axis and Long-Axis Orientation. The figure shows a representative example of the tracking in Short-Axis and Long-Axis Orientation of the left ventricle (LV) and the right ventricle (RV).

Figure 2

Circumferential and radial strain in respect to changes of left ventricular ejection fraction. The figure shows changes in circumferential and radial strain in respect to changes of left ventricular ejection fraction (EF) at rest and with dobutamine stress (10 and 20 μg/kg^-1/min^-1). Values expressed as mean with standard deviation. LV = left ventricle, EF = ejection fraction.

Figure 3

Bland Altman Plots for intra- and inter-observer variability. Bland Altman Plots for intra- and inter-observer variability obtained for all strain parameters at rest on a segmental basis

Figure 4

Bland Altman Plot showing the relationship between Err_SAX and natural radial strain. Bland Altman Plot showing the relationship between Err_SAX (Mean 19.6; 15.8-23.4 95% confidence interval) and natural radial strain (Mean 24; 21.7-26.4 95% confidence interval). Err_SAX = left ventricular short-axis radial strain