Value of Feature-Tracking CMR in Dilated Cardiomyopathy
What is the prognostic value of cardiac magnetic resonance (CMR) feature-tracking–derived global longitudinal strain (GLS) in dilated cardiomyopathy?
The study cohort was comprised of consecutive patients undergoing CMR with ejection fraction (EF) <50% and ischemic or nonischemic dilated cardiomyopathy at four US medical centers. The study authors calculated feature-tracking GLS from three long-axis cine-views. The primary endpoint was all-cause mortality. Cox proportional hazards regression modeling was used to examine the association between GLS and mortality. The incremental prognostic value of GLS was assessed in nested models.
The final study cohort was comprised of 1,012 patients (505 ischemic and 507 nonischemic), of whom 133 died during a median follow-up of 4.4 years. The mean age of the study population was 60 ±16 years. Sixty-five percent of patients were male, and 31% had diabetes mellitus. The mean EF was 33.7 ± 10.0%. Mean GLS for the population was -10.9%. Median GLS was -11.0% (interquartile range, -7.8 to -14.0%). Using Kaplan-Meier analysis, the investigators found that the risk of death increased significantly with worsening GLS tertiles (log-rank p < 0.0001). There was an 89.1% increased risk of death with each 1% worsening in GLS after adjusting for clinical and imaging risk factors including age, body mass index, diabetes, hyperlipidemia, left ventricular end-diastolic volume index, EF, and late gadolinium enhancement (LGE) (hazard ratio [HR], 1.891 per %; p < 0.001). There was a significant improvement in the C-statistic with addition of GLS in this model (0.628-0.867; p < 0.0001). Continuous net reclassification improvement was 1.148 (95% confidence interval, 0.996-1.318). In patients with ischemic cardiomyopathy, each 1% worsening in GLS was associated with a 94.2% increased risk of death after adjustment for clinical and imaging risk factors (HR, 1.942 per %; p < 0.001). Similarly, in patients with nonischemic dilated cardiomyopathy, GLS remained significantly associated with death after adjustment for clinical and imaging risk factors (HR, 2.101 per %; p < 0.001).
The study authors concluded that CMR feature-tracking–derived GLS is a powerful independent predictor of mortality in a multicenter population of patients with ischemic or nonischemic dilated cardiomyopathy, incremental to common clinical and CMR risk factors including EF and LGE.
This is an important study, which demonstrates that feature-tracking CMR (FT-CMR) adds incremental value to current parameters such as EF and LGE. If other studies can reproduce these important findings, FT-CMR should emerge as the gold standard in the assessment of cardiac function.
Keywords: Cardiomyopathy, Dilated, Diabetes Mellitus, Diagnostic Imaging, Gadolinium, Heart Failure, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Ischemia, Risk Factors, Stroke Volume, Ventricular Function, Left
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