Independent Prognostic Significance of Myocardial Flow Reserve over Coronary Artery Calcium, Myocardial Perfusion, and Clinical Variables in Patients without Known CAD, according to Diabetes Status.

Abstract

Objective: To explore differences in prevalence and prognosis associated with reduced myocardial flow reserve (MFR) in patients without known coronary artery disease (CAD) based on diabetes status.

Methods: Of 2,639 patients without known CAD who underwent rubidium positron emission tomography myocardial perfusion imaging (MPI), 818 patients (31%) had diabetes. Reduced MFR was defined as MFR <2.0. Coronary artery calcification (CAC) score was categorized as 0, 1-99, 100-399, and ≥ 400. Ischemic total perfusion deficit (TPD) was categorized as <1%, 1-<5%, and ≥ 5%. Outcome variables were all-cause death (ACD) and non-fatal myocardial infarction (MI).

Results: During median follow-up of 4.1 year, 574 (21.8%) ACD/MI occurred (204 [25.1%] diabetic patients, 370 [20.3%] non-diabetic patients). In multivariable Cox analysis, reduced MFR was associated with increased ACD/MI in patients with diabetes (per 0.1 decrease: HR: 1.04, 95% CI: 1.02-1.06, P < 0.001) and patients without diabetes (per 0.1 decrease: HR: 1.03, 95% CI: 1.02-1.04, P < 0.001). No interaction existed between diabetes and MFR for ACD/MI risk regardless of CAC or ischemic burden (all p > 0.05). Adding MFR to the risk prediction model of clinical, conventional MPI findings, and CAC improved the discrimination for clinical outcomes in both groups (DM: 0.003, non-DM: <0.001, respectively).

Conclusion: Reduced MFR was more common in patients with diabetes and an important independent prognostic marker over CAC and clinical variables. The association between MFR and ACD/MI risk did not differ between patients with and without diabetes who had no prior CAD, regardless of CAC and ischemic burden.