A comparison between radial strain evaluation by speckle-tracking echocardiography and cardiac magnetic resonance imaging, for assessment of suitable segments for left ventricular lead placement in cardiac resynchronization therapy.

AIMS: A cut-off of 9.8% maximum speckle-tracking radial strain in the segment with the latest mechanical delay has been proposed as predictive for selecting the best left ventricular lead placement for positive response on cardiac resynchronization therapy (CRT). However, pacing transmural scar should be avoided, and the purpose of this study was to evaluate the ability of echocardiographic radial strain to predict the presence of scar in the left ventricle segments. METHODS AND RESULTS: A total of 404 left ventricular segments were analysed, from 34 patients eligible for CRT. Pre-operative cardiac magnetic resonance (CMR) and echocardiography were performed, and maximal strain values from echocardiography speckle tracking were compared with CMR data. Hypokinesia and strain values showed a strong correlation (P < 0.001). Even though segments with CMR-verified scar had lower strain values than segments without scar (14.8 ± 7 vs. 16.0 ± 10), the predictive value of the proposed 9.8% cut-off was low (sensitivity 33% and specificity 72%). Scar burden was higher in ischaemic patients (13.5 vs. 5.3% P = 0.0001). Relative difference in strain values (target segment strain compared with the average strain value of the adjacent segments) was higher if there was transmural scar in the target segment as compared with a hypokinetic but viable target segment (87 vs. 38% difference, P = 0.03). CONCLUSION: Speckle tracking radial strain should ideally be complemented by CMR for accurate assessment of viability, especially for patients with ischaemic aetiology of heart failure where transmural scar is more common. Comparison of strain values with the adjacent segments may be helpful for assessing viability.