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Purpose: Echocardiographic assessment of left ventricular (LV)systolic function represents a mainstay in the follow-up of cardiac transplanted patients(c-Tx). However ejection fraction might be preserved despite evidence of rejection and/or severe vasculopathy. Thus,more sensitive markers of subclinical systolic dysfunction are needed for an accurate evaluation of risk in c-Tx. Aim of the study is to describe LV systolic function in c-Tx pediatric patients through the analysis of speckle tracking echocardiography (STE).Methods: 55c-Tx patients and 10 healthy volunteers underwent standard 2dimensional echocardiographic examination with STE analysis (iE33, Philips, Andover, MA, USA). Circumferential (Cε), longitudinal (Lε) strain and LV rotation were analyzed.The difference between the apical clockwise rotation and the basal counterclockwise rotation of the LV was computed to derive LV torsion(expressed in °per cm of LV lenght).Data from the c-Tx were compared to the control group as well as to previously published age-specific partition values, to define the prevalence of clear-cut systolic dysfunction.Results: Patients with rejection, coronary artery occlusion, EF< 55%, inadeguate echocardiographic images and/or with transplant performed less than 4 months before were excluded.Analysis was thus available in 40 c-Tx(LV torsion in 50% of the sample).Mean time from heart transplant was 5.8 years.No differences were observed among groups in LV ejection fraction (66% vs 67%),fractional shortening, mitral Doppler inflow pattern or mitral E/e' ratio (all p=ns). In c-Tx, mean strain values were significantly reduced in Lε as compared to normals(−15% vs −25%; p<0.001) with similar Cε among groups (−17% vs −19%; p=ns).Accordingly,clear-cut reduced strain was common in c-Tx as compared to normals (58% vs 0%: p<0.001), demonstrating a high prevalence of systolic dysfunction despite normal ejection fraction in this patient population. LV torsion was also markedly reduced in c-Tx as compared to normals (1.11°/cm vs 0.77°/cm; p<0.01), due to a significant reduction in basal rotation (−2.4° vs −3.8° in normals; P<0.05).Conclusions: In the presence of normal ejection fraction, over one in two c-Tx patients show evidence of LV systolic dysfunction.Main culprit for this impairment is the reduction in LV longitudinal function (despite preserved circumferential strain) which results in reduced basal rotation and thus blunted LV torsion.Analysis of STE is of incremental utility in the evaluation of pediatric c-Tx patients also when EF is normal.Prospective studies are needed to establish the prognostic impact of our findings.