1004 Relation between three-dimensional echocardiography derived left ventricular volume and MRI derived circumferential strain in patients eligible for cardiac resynchronization therapy
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KeywordsStrain Curve Cardiac Resynchronization Therapy Volume Curve Circumferential Strain Mechanical Dyssynchrony
Mechanical dyssynchrony (MD) is thought to be a better predictor for response to cardiac resynchronization therapy (CRT) than electrical dyssynchrony. Several methods using either ultrasound or MRI are used to quantify MD. Theoretically, three-dimensional (3D) left ventricular (LV) volume and circumferential strain seem related, since both measures are connected to the radius (r) of the ventricle. Failing dilated hearts become more spherical, therefore their volume is proportional to r3. Circumferential strain describes length changes in the circumference of the LV (2πr) and can therefore be described as (rn-r1)/r1, where n is a time point in the cardiac cycle and r1 is constant. The purpose of this study was to compare regional LV volume curves obtained with 3D ultrasound with LV circumferential strain curves obtained by MRI in CRT candidates, to investigate whether it is likely that quantification of LV MD will give the same results for both methods.
In thirteen patients with chronic heart failure, 3D ultrasound and tagged MRI were performed subsequently. During post-processing, regional LV volume was computed from the ultrasound images by dividing a LV cast in pie shaped segments using a central line of gravity that is moving over time. From the tagged MR images, regional circumferential strain was calculated using the harmonic phase method . The first 16 segments from the standard 17-segment model  were used, leading to a total of 208 segments to be compared. Cross-correlations with time lags of 1% of the cardiac cycle were performed to compare the curves in corresponding LV segments. MR delayed contrast enhancement (DCE) was used to detect scar tissue. The relation between the location of DCE and the cross-correlation was explored.
Results and discussion
High correlations were observed between circumferential strain and volume curves, but regional differences in time-delay were found, especially in segments with abnormal, positive strain curves. This possibly hampers the comparison of both measures for the quantification of MD.
This article is published under license to BioMed Central Ltd.