P928Regional heterogeneity in myocardial susceptibility to catecholamine-induced cardiotoxicity.

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Purpose: Regional myocardial deformation patterns are important in many cardiac diseases, including stress-induced cardiomyopathy (SIC). Speckle-tracking echocardiography (STE) allows for in-depth cardiac phenotyping in humans and has recently been introduced in small animal laboratories. We hypothesize that regional perturbations in cardiac function may occur during severe catecholamine stress and that STE may be able to detect and quantify these perturbations.Methods: 10 C57BL/6 mice underwent baseline echocardiographic examination using ECG-gated Kilohertz visualization technique to acquire cine loops of >1000 frames/s (VisualSonics VEVO770 system). In a parasternal short axis (SAX) cine loop, the heart was divided into six segments and regional fractional wall thickening (FWT) was assessed manually. The protocol was repeated in 7 mice 90 minutes post 400 mg/kg i.p isoprenaline (ISO).In another 23 C57BL/6 mice regional transmural radial strain and strain-rate were calculated in a SAX cine loop using VisualSonics VEVO2100 system and the velocity vector imaging (VVI) STE algorithm.Results: Regional myocardial FWT is uniform at baseline but decreases significantly in posterior segments compared to anterolateral segments after ISO (p<0.05). A similar pattern is seen in VVI-derived data, although the differences fail to reach significance.Conclusions: Severe ISO-stress causes posterior wall myocardial dysfunction, represented by decreased regional FWT. This finding indicate heterogeneity in the susceptibility of the myocardium to high catecholamine levels. In the mouse, available STE algorithms are less sensitive in detecting regional perturbations in myocardial function than manual tracing, possibly because of a too low frame-rate in the cine loops used, which leads to speckle decorrelation.

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