Abstract Body (Do not enter title and authors here): Background: The pathophysiological and clinical significance of coronary microvascular dysfunction in patients with diabetes mellitus and heart failure with preserved ejection fraction (HFpEF) remains uncertain.
Research Questions: We aimed to use cardiac magnetic resonance to quantify coronary microvascular function, explore the relationship between perfusion and fibrosis, and assess the impact of coronary microvascular function on long-term clinical outcomes.
Methods: In a prospective, observational study, patients with type 2 diabetes (T2DM) and heart failure were recruited alongside control subjects. All participants underwent clinical assessment and cardiac magnetic resonance, which included T1 mapping, extracellular volume mapping, as well as measurement of myocardial blood flow at rest and during maximal hyperaemia. The primary endpoint was defined as the composite outcome of death or hospitalization with a cardiovascular cause.
Results: A total of 65 control individuals and 443 patients with T2DM were screened. Of 167 T2DM patients in the final analysis, 55 (32.9%) patients were categorized as HFpEF, 70 (41.9%) as heart failure with ejection fraction less than 50% (DM-non-HFpEF), and 42 (25.1%) as control subjects with no heart failure (DM-control). Patients with DM-HFpEF exhibited a comparatively diminished myocardial perfusion reserve (MPR) in comparison to the other three cohorts (all P<0.05). Coronary microvascular function (defined as MPR <2.0) was present in 81.82% of patients with DM-HFpEF. MPR was associated with cardiac troponin T levels (r =-0.3687; P<0.0001) and diffuse fibrosis (extracellular volume: r =-0.5941; P<0.0001). In all participants, during a mean follow-up of 284 days, there were 47 composite events. MPR demonstrated independent predictability of clinical outcomes even adjusting for clinical, blood, and imaging parameters. Patients with lower MPR (cutoff point, 1.95) exhibited a higher risk of adverse outcomes compared with patients with higher MPR (P=0.0001).
Conclusions: In symptomatic patients with T2DM, a high prevalence of impaired MPR was observed specifically in individuals with HFpEF. MPR was associated with makers of myocardial injury and fibrosis and was predictive of adverse clinical outcomes. These findings could help identify high-risk patients, leading to more intensive treatment.