Abstract
Cardiac magnetic resonance imaging (MRI) with late gadolinium enhancement (LGE) is considered the gold standard for scar detection after myocardial infarction. In times of increasing skepticism about gadolinium depositions in brain tissue and contraindications of gadolinium administration in some patient groups, tissue strain-based techniques for detecting ischemic scars should be further developed as part of clinical protocols. Therefore, the objective of the present work was to investigate whether segmental strain is noticeably affected in chronic infarcts and thus can be potentially used for infarct detection based on routinely acquired non-contrast cine images in patients with known coronary artery disease (CAD). Forty-six patients with known CAD and chronic scars in LGE images (5 female, mean age 52 ± 19 years) and 24 gender- and age-matched controls with normal cardiac MRI (2 female, mean age 47 ± 13 years) were retrospectively enrolled. Global (global peak circumferential [GPCS], global peak longitudinal [GPLS], global peak radial strain [GPRS]) and segmental (segmental peak circumferential [SPCS], segmental peak longitudinal [SPLS], segmental peak radial strain [SPRS]) strain parameters were calculated from standard non-contrast balanced SSFP cine sequences using commercially available software (Segment CMR, Medviso, Sweden). Visual wall motion assessment of short axis cine images as well as segmental circumferential strain calculations (endo-/epicardially contoured short axis cine and resulting polar plot strain map) of every patient and control were presented in random order to two independent blinded readers, which should localize potentially infarcted segments in those datasets blinded to LGE images and patient information. Global strain values were impaired in patients compared to controls (GPCS p = 0.02; GPLS p = 0.04; GPRS p = 0.01). Patients with preserved ejection fraction showed also impeded GPCS compared to healthy individuals (p = 0.04). In patients, mean SPCS was significantly impaired in subendocardially (− 5.4% ± 2) and in transmurally infarcted segments (− 1.2% ± 3) compared to remote myocardium (− 12.9% ± 3, p = 0.02 and 0.03, respectively). ROC analysis revealed an optimal cut-off value for SPCS for discriminating infarcted from remote myocardium of − 7.2% with a sensitivity of 89.4% and specificity of 85.7%. Mean SPRS was impeded in transmurally infarcted segments (15.9% ± 6) compared to SPRS of remote myocardium (31.4% ± 5; p = 0.02). The optimal cut-off value for SPRS for discriminating scar tissue from remote myocardium was 16.6% with a sensitivity of 83.3% and specificity of 76.5%. 80.3% of all in LGE infarcted segments (118/147) were correctly localized in segmental circumferential strain calculations based on non-contrast cine images compared to 53.7% (79/147) of infarcted segments detected by visual wall motion assessment (p > 0.01). Global strain parameters are impaired in patients with chronic infarcts compared to controls. Mean SPCS and SPRS in scar tissue is impeded compared to remote myocardium in infarcts patients. Blinded to LGE images, two readers correctly localized 80% of infarcted segments in segmental circumferential strain calculations based on non-contrast cine images, in contrast to only 54% of infarcted segments detected due to wall motion abnormalities in visual wall motion assessment. Analysis of segmental circumferential strain shows a promising method for detection of chronic scars in routinely acquired, non-contrast cine images for patients who cannot receive or decline gadolinium.
Highlights
Cardiac magnetic resonance imaging (MRI) with late gadolinium enhancement (LGE) is considered the gold standard for scar detection after myocardial infarction
Global strain values were reduced in patients compared to healthy controls (GPCS − 10.5% ± 3 vs. − 20.6% ± 2, p = 0.02; GPLS – 11.8% ± 3 vs. – 18.2% ± 2, p = 0.04; GPRS 27.5% ± 6 vs. 39.6% ± 4; p = 0.01, Table 1), interobserver agreement was good or excellent (Table 2)
Patients with preserved Left ventricular ejection fraction (LVEF) (LVEF > 50%, 19 patients)[30] had markedly reduced GPCS compared to healthy individuals (− 12.3% ± 2 vs. − 20.6% ± 2, p = 0.04), while GPLS and GPRS was not significantly impaired (GPLS − 13.6% ± 4 vs. − 18.2% ± 2, p = 0.2; GPRS 33.4% ± 6 vs. 39.6% ± 5, p = 0.3) (Fig. 2)
Summary
Cardiac magnetic resonance imaging (MRI) with late gadolinium enhancement (LGE) is considered the gold standard for scar detection after myocardial infarction. 80.3% of all in LGE infarcted segments (118/147) were correctly localized in segmental circumferential strain calculations based on non-contrast cine images compared to 53.7% (79/147) of infarcted segments detected by visual wall motion assessment (p > 0.01). Abbreviations AUC Area under the curve FT Feature tracking GPCS Global peak circumferential strain GPLS Global peak longitudinal strain GPRS Global peak radial strain ICC Intraclass correlation coefficient i.v. Intravenous LGE Late gadolinium enhancement LV Left ventricle/left-ventricular LVEDV Left ventricular end-diastolic volume LVEF Left ventricular ejection fraction LVESV Left ventricular end-systolic volume LVSV Left ventricular stroke volume MRI Magnetic resonance imaging MI Myocardial infarction ms Milliseconds min Minute(s) ROC Receiver operating characteristics s Seconds SPCS Segmental peak circumferential strain SPLS Segmental peak longitudinal strain SPRS Segmental peak radial strain SSFP Steady-state free precession T Tesla. Scar tissue leads to regionally altered strain behavior of the myocardium due to reduced contractility of myofibroblasts, which replace myocytes after infarction[12]
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