Background Left ventricular ejection fraction (LVEF) is relatively indiscriminate for prognosis in patients with preserved or mildly reduced LVEF (>40%) following myocardial infarction (MI). This study sought to determine the value of guideline-based assessment of diastolic dysfunction (DD) in predicting long-term all-cause and cardiac mortality in patients with a first-ever MI and LVEF>40%.

Methods A retrospective single centre study involving 2234 patients with a first-ever MI (STEMI or NSTEMI) with LVEF>40% was performed. Clinical, angiographic, echocardiographic and outcomes data were obtained from prospectively maintained institutional and state-wide databases. Echocardiography was performed early post-admission for all patients. Significant diastolic dysfunction (DD) was defined was grade 2&3 diastolic dysfunction.

Results The mean age of patients was 61.4+12.3 years, 70.7% were males, and 12.1% had 3-vessel disease. The mean LVEF was 55.8+7.2% and 14.1% had significant DD. At a median follow up of 4.5 years, there were 219 deaths (46 cardiac deaths). On Cox proportional-hazards multivariable analyses incorporating significant clinical, angiographic, and echocardiographic variables, significant DD was an independent predictor of both all-cause (HR 2.01, 95%CI 1.37-2.94, p<0.001) and cardiac (HR 3.97, 95%CI 1.98-7.99, p<0.001) mortality. Bootstrapping and calculation of Harrel’s C confirmed the independent association of significant DD with outcomes.

Conclusions Significant DD is an independent predictor of all-cause and cardiac mortality following MI in patients with preserved or mildly reduced LVEF and thus effectively re-classifies prognosis in a subgroup where the LVEF is relatively indiscriminate for survival. The benefit of further investigation and/or treatment in this subgroup needs further study.