Abstract Body (Do not enter title and authors here): Introduction/Background
Cardiomyopathy is the leading cause of death in Duchenne muscular dystrophy (DMD). While cardiac magnetic resonance (CMR) is used routinely to assess fibrosis and left ventricular ejection fraction (LVEF), CMR measures of LV filling and ejection in DMD have not been reported.

Hypothesis
We hypothesized that patients with DMD would have abnormal LV filling and ejection measures compared to healthy controls and that these measures would associate with mortality.

Aims
We aimed to assess LV filling and ejection curves in patients with DMD compared to healthy controls and whether these measures associate with mortality.

Methods
Prospectively enrolled DMD patients and healthy controls underwent CMR, including LVEF and LV filling and ejection curves. Multivariable linear regressions were used to compare filling and ejection measures between groups to adjust for baseline differences. Cox regressions were used to evaluate the relationship between diastolic function measures and mortality in the DMD cohort.

Results
A total of 179 patients with DMD (mean age 14.3 years) and 96 healthy controls (mean age 14.4 years) were included. DMD patients had lower baseline LVEF, though most (112, 62%) had normal systolic function. When adjusted for age, sex, heart rate, body surface area, and left ventricular end diastolic volume (LVEDV), patients with DMD had slower peak LV filling rates (PFR) and peak LV ejection rates (PER) as well as slower time to PER (Table 1). When limited to DMD patients with normal LVEF, PER remained slower. When adjusted for heart rate, lower PER and PFR normalized to LVEDV were associated with mortality in patients with DMD (Table 2).

Conclusions
Patients with DMD have different baseline CMR filling and ejection indices compared with controls, including when limited to DMD patients with normal LVEF. While filling indices associate with mortality in the short-term, longitudinal follow-up is needed to refine their prognostic role in DMD.