Introduction: Dysregulated myocardial calcium handling may be a precursor for heart failure in type 1 (T1D) and type 2 diabetes (T2D). Manganese-enhanced magnetic resonance imaging (MEMRI) is a novel non-invasive method of assessing in vivo myocardial calcium handling. Hypothesis Myocardial calcium handling is impaired in patients with either T1D or T2D, despite normal left ventricular (LV) systolic function. Methods Prospective, multicentre, study in patients with T1D (n=19), T2D (n=30), and healthy volunteers (n=28), all of whom were free of known cardiovascular disease. Cardiac MRI was performed including MEMRI, during which T1 mapping was performed at baseline and every 2.5 min for 30 min after manganese infusion (Figure 1a). The rate of myocardial manganese uptake, determined by Patlak modelling [1]. Results No difference in LV systolic function was observed between groups, but those with T2D had more concentric LV remodelling compared to T1Ds and healthy volunteers (LV mass:volume 0.90±0.16 vs. 0.75±0.09 vs. 0.74±0.10 g/mL, respectively; p=0.001, Table 1). Mean myocardial manganese uptake was significantly lower in both T1Ds (6.47±0.99 mL/100g/min) and T2Ds (6.43±0.77 mL/100g/min) compared with healthy volunteers (8.33±0.77 mL/100g/min; p<0.001 for both, Figure 1b). Conclusion For the first time, we have demonstrated that myocardial calcium handling is impaired in patients with either T1D or T2D despite apparently normal LV systolic function. This may be a precursor to the development of diabetic cardiomyopathy and has implications for developing novel therapeutic targets for its prevention and treatment. [1] Skjold, A et al. J Magn Reson Imag 2006;24:1047-1055 graphic_{ECFA3EC4-96D0-4ADC-8599-3D854C84F04F}graphic_{F1770AC6-718C-4C39-B107-4A5DD60957A8}