It is well known that abnormalities in cardiac function are common in both children and adults with chronic kidney disease (CKD). In fact, complicating cardiac disease continues to be the leading cause of mortality in patients with end stage renal disease.The most common cardiac complication of CKD is left ventricular hypertrophy (LVH). In adults, the presence of systolic dysfunction is the leading echocardiographic marker of impending cardiac failure and death. Assessing this in children is not easy; the echocardiographic measurement of systolic function by endocardial shortening fraction may not be accurate in the presence of LVH. To avoid this source of error, it has been suggested that another measure, midwall shortening fraction (mwSF), be employed.In this issue of The Journal, Weaver et al provide an extensive study of mwSF in children with CKD. These investigators, with a longstanding interest in the cardiac complication of CKD in children, examined mwSF in healthy children, children with CKD, children on hemodialysis, and children after renal transplantation. The authors have now shown that there are significant abnormalities in mwSF in children with CKD; it appears to be related to the severity of the CKD because it is more impaired in children on hemodialysis than in those with degrees of CKD not requiring renal replacement therapy.Although mwSF has proven to be a marker of mortality risk in adults with CKD, Weaver et al have thus far provided us only with a “snapshot” of this measure in a group of children. Longitudinal studies, presumably ongoing, will show if this marker is as powerful a predictor of the risk of cardiac events in children as it is in adults. It is well known that abnormalities in cardiac function are common in both children and adults with chronic kidney disease (CKD). In fact, complicating cardiac disease continues to be the leading cause of mortality in patients with end stage renal disease. The most common cardiac complication of CKD is left ventricular hypertrophy (LVH). In adults, the presence of systolic dysfunction is the leading echocardiographic marker of impending cardiac failure and death. Assessing this in children is not easy; the echocardiographic measurement of systolic function by endocardial shortening fraction may not be accurate in the presence of LVH. To avoid this source of error, it has been suggested that another measure, midwall shortening fraction (mwSF), be employed. In this issue of The Journal, Weaver et al provide an extensive study of mwSF in children with CKD. These investigators, with a longstanding interest in the cardiac complication of CKD in children, examined mwSF in healthy children, children with CKD, children on hemodialysis, and children after renal transplantation. The authors have now shown that there are significant abnormalities in mwSF in children with CKD; it appears to be related to the severity of the CKD because it is more impaired in children on hemodialysis than in those with degrees of CKD not requiring renal replacement therapy. Although mwSF has proven to be a marker of mortality risk in adults with CKD, Weaver et al have thus far provided us only with a “snapshot” of this measure in a group of children. Longitudinal studies, presumably ongoing, will show if this marker is as powerful a predictor of the risk of cardiac events in children as it is in adults.