Aims: Coronary flow reserve (CFR) and coronary calcium score (CCS) represent different aspects of atherosclerosis. We examined the prevalence and predictors of reduced CFR and high CCS in type 2 diabetes (T2DM) patients free of overt cardiovascular disease compared to non-diabetic controls.

Methods: Cross-sectional study of 60 T2DM patients stratified by normoalbuminuria (<30mg/24h) (n=30; age (mean±SD) 60.9±10.1 years; 40% women) and albuminuria (≥30mg/24h) (n=30; 65.6±4.8 years; 27% women) randomly selected from our outpatient clinic and 30 non-diabetic controls (59.8±9.9 years; 40% women) undergoing cardiac ⁸²Rb PET/CT.

Results: In controls, normoalbuminuric, and albuminuric patients CFR was 3.0±0.8, 2.6±0.8, and 2.0±0.5 (P<0.001); frequency of reduced CFR (<2.5) was 16.7, 40.0, and 83.3% (P<0.001); and CCS (median[IQR]) was 0[0–81], 36[1–325], and 370[152–1025] (P<0.001), respectively. After comprehensive adjustment, CFR remained significant higher (P=0.023) and CCS significant lower (P=0.020) in normoalbuminuric vs. albuminuric patients. The univariate association between CFR and CCS was significant in control subjects (R²=0.23; P=0.007), but not in normoalbuminuric or albuminuric patients (R²≤0.10; P≥0.09). However, after adjustment lower CFR was related to higher CCS, UAER, age, heart rate, lower HbA_1C, and male gender (P≤0.047) in albuminuric patients; and to female gender (P=0.024) in normoalbuminuric patients. Higher CCS was related to lower CFR and UAER (P≤0.048) in albuminuric patients; and to higher HbA_1C in controls (P=0.033).

Conclusion: T2DM patients free of overt cardiovascular disease had a high prevalence of coronary microvascular dysfunction, especially with concomitant albuminuria. This was not explained by elevated CCS. Prospective studies are needed to show the prognostic significance.