Ejection fraction (EF) measured by contemporaneous echocardiography and cardiovascular magnetic resonance (CMR) correlate only moderately (panel A), and there is considerable scatter and misclassification. Bland-Altman analysis (panel B) reveals that this scatter does not result from systematic bias. Importantly, most of scatter occurs in the 30%-50% range of the EF spectrum where clinical decision making relies most heavily on EF measures as shown by the thin gray box in panel B. Of note, variation far exceeded the ∆ 5% increment used for EF reporting by echocardiography. In Panel C, despite similar median EF values and the absence of meaningful bias in the EF measures of the population, the scatter exhibited by the individual differences in echocardiography and CMR EF measures culminate in 102 individuals (23%) of the sample being categorized differently (highlighted in bold font).