Vitamin D and Left Ventricular Dysfunction in pediatric dialysis patients; A Tissue Doppler study. Seham M Ramadan, Hadeel M Abdelrahman, Nashwa M Al Azizi, Heba Abouzeid Collaborative paper, derived from thesis, Accepted for publication in: MINERVA PEDIATRICS Background: Assessment of the left ventricular function in the dialysis children and explore its association with vitamin D level and markers reflecting calcium and phosphate metabolism. Methodsː In this case-control study, we enrolled forty children on regular hemodialysis and forty healthy controls from July 2019 to March 2020 at the pediatric dialysis unit. Echocardiographic evaluation using both conventional and Tissue Doppler Imaging (TDI) was done for all subjects. Vitamin D and its markers were analyzed to assess its association with ventricular dysfunction. Resultsː Diastolic function in children on hemodialysis was significantly impaired as evidenced by lower Mitral E/A velocity ratio, lower early diastolic velocity (Eˊ), and higher E/Eˊ ratio (Ratio of early diastolic mitral inflow velocity (measured by pulsed wave traditional Doppler) to early diastolic mitral annular velocity (measured by Tissue Doppler). in comparison with the controls. Most end stage renal disease (ESRD) participants had vitamin D deficiency. There was an important correlation between left ventricular (LV) dysfunction and both Vitamin D deficiency and hyperparathyroidism. Although our patients had normal systolic function by conventional and Tissue Doppler echocardiographic study, mean values of TDI- MPI (Tissue Doppler Imaging Derived Myocardial Performance Index) in the hemodialysis group were significantly higher than in the control group, which indicates impaired global cardiac systolic and diastolic function. Conclusionsː Tissue Doppler Imaging (TDI) provides a good reflection of the LV diastolic function. As vitamin D deficiency has been substantially associated with worsening of LV dysfunction, we suggest that TDI and Vitamin D might be included in the routine follow-up of pediatric dialysis patients.