Strain analysis using feature tracking cardiac magnetic resonance (FT-CMR) in the assessment of myocardial viability in chronic ischemic patients

The purpose of this study is to test the capability of a commercially available feature tracking-cardiac magnetic resonance (FT-CMR) strain analysis software module in differentiating between viable and non-viable myocardium in chronic ischemic patients. Thirty chronic ischemic patients and 10 healthy volunteers were enrolled. Cine images were used for peak circumferential and radial strains quantification using dedicated FT-CMR software. Global strain was compared between patients and controls. In patients, segmental strain was compared in viable and non-viable myocardium determined by late gadolinium enhancement (LGE); and in segments with wall abnormalities. Among 480 myocardial segments analyzed in patients, 76 segments were non-viable on LGE. The mean left ventricular ejection fraction (LVEF) of the patients (87% males, mean age 55 +/- 12 years) was 40 +/- 12% vs. 61 +/- 5% for the controls (80% males, mean age 39 +/- 11 years). Peak global circumferential strain (GCS) and global radial strain (GRS) were significantly impaired in patients compared to controls (-13.89 +/- 4.12% vs. -19.84 +/- 1.47%), p < 0.001 and (23.11 +/- 6.59% vs. 31.72 +/- 5.52%), p = 0.001. Segmental circumferential strain (SCS) and segmental radial strain (SRS) were significantly impaired in non-viable compared to viable segments (-9.47 +/- 7.26% vs. -14.72 +/- 7.5%), p < 0.001 and (15.67 +/- 12.11% vs. 24.51 +/- 16.22%), p < 0.001. Cut-off points of -9.36% for the SCS (AUC = 0.7, 95% CI = 0.63-0.77) and 19.5% for the SRS (AUC = 0.67, 95%CI = 0.61-0.73) were attained above which the segment is considered viable. SCS was able to discriminate between normokinetic, hypokinetic and akinetic segments (mean = 27.6 +/- 17.13%, 18.66 +/- 12.88% and 15.24 +/- 10.70% respectively, p < 0.001). Circumferential and radial segmental strain analysis by FT-CMR was able to discriminate between viable and non-viable segments of the myocardium defined by LGE and between normokinetic, hypokinetic and akinetic segments, using routinely acquired cine images, and thus can provide a more objective metric for risk stratification in chronic ischemic patients.