Insights into ventricular cardiac function by MRI in patients with iron overload

Purpose:

Preserved left ventricular (LV) function is often seen in patients with myocardial iron overload. Cardiac iron assessed by GRE-MRI-R2* methods is the earliest predictor of cardiac morbidity in iron overload disease. The aim of this study was to evaluate early LV function parameters of cardiomyopathy due to cardiac iron overload.

Patients and Methods:

In 27 patients and subjects (10–58y), LV function parameters and the transversal relaxation rate R2* (=1/T2*) was determined from 6mm short and long (4- and 2-chamber view) axis slices. Breathhold retrospective ECG gating was used on a 1.5 T imager acquiring data with 8 echo times (TE 1.9–21.5ms) in end-diastole (TR=223ms, flip angle=20°). LV function was assessed from cine-SSFP series (25 phases). A wire model (CMRtools®) with precise valve and individual blood-tissue threshold adjustment was used for temporal volumetry. Left ventricular ejection fraction (LVEF), the end-diastolic (EDV), and end-systolic (ESV) volumes were determined by the Teichholz, the combined tri-plane (C3P), and the 3-dimensional volumetric method, both including (3D-inp) and excluding (3D-exp) papillary muscles. The ratio of the late to the early (atrial) peak filling rate (PFR) was determined from the first temporal differentiation of the LV.

Results:

LVEF of the 3D-inp method (=reference) agreed with the Teichholz (r²=0.73), C3P (r²=0.87), 3D-exp (r²=0.96) method with comparable coefficients of determination r². The proportional bias was higher for Teichholz (4%), C3P (8%), and 3D-exp (8%). Similarly, EDV and ESV (r²=0.92–0.99) showed 25% lower volumes for the Teichholz and expected lower volumes for the 3D-exp method. LVEF<56–60% was only found for septal R2*>50s^-1, without significant correlation of R2*. PFR ratios could only be determined by the 3D-exp with a significant positive correlation with septal R2* (r²=0.56, p<0.03).

Conclusion:

LVEF can be determined accurately with nearly all ventricular geometry models; however, EDV and ESV can be determined best by the C3P model or the 3D method. With respect to the earliest signs of impaired diastolic function due to elevated cardiac iron, the PFR ratio may be superior to LVEF.

Clinical relevance:

C3P method is sufficient to diagnose impaired LV function, but early detection of cardiomyopathy may require more sensitive 3D analysis with accurate temporal differentiation of the ventricular volume