Background-The pathogenic role of ischemic heart disease (IHD) in heart failure (HF) with reduced ejection fraction (HFrEF; EF amp;lt;40%) is well established, but its pathogenic and prognostic significance in HF with midrange (HFmrEF; EF 40%-50%) and preserved EF (HFpEF; EF amp;gt;= 50%) has been much less explored. Methods and Results-We evaluated 42 987 patients from the Swedish Heart Failure Registry with respect to baseline IHD, outcomes (IHD, HF, cardiovascular events, and all-cause death), and EF change during a median follow-up of 2.2 years. Overall, 23% had HFpEF (52% IHD), 21% had HFmrEF (61% IHD), and 55% had HFrEF (60% IHD). After multivariable adjustment, associations with baseline IHD were similar for HFmrEF and HFrEF and lower in HFpEF (risk ratio, 0.91 [0.89-0.93] versus HFmrEF and risk ratio, 0.90 [0.88-0.92] versus HFrEF). The adjusted risk of IHD events was similar for HFmrEF versus HFrEF and lower in HFpEF (hazard ratio, 0.89 [0.84-0.95] versus HFmrEF and hazard ratio, 0.84 [0.80-0.90] versus HFrEF). After adjustment, prevalent IHD was associated with increased risk of IHD events and all other outcomes in all EF categories except all-cause mortality in HFpEF. Those with IHD, particularly new IHD events, were also more likely to change to a lower EF category and less likely to change to a higher EF category over time. Conclusions-HFmrEF resembled HFrEF rather than HFpEF with regard to both a higher prevalence of IHD and a greater risk of new IHD events. Established IHD was an important prognostic factor across all HF types.