Abstract
BACKGROUND: It has been suggested that coronary microvascular function decreases with age, irrespective of the presence of epicardial atherosclerosis. AIMS: Our aim is to quantitatively investigate the effects of age on microvascular function in patients with normal coronary arteries. METHODS: In 314 patients with angina with no obstructive coronary artery disease (ANOCA), microcirculatory function was tested using the continuous thermodilution method. In 305 patients, the association between age and both resting and hyperaemic myocardial blood flow (Q), microvascular resistance (R(μ)), absolute coronary flow reserve (CFR) and microvascular resistance reserve (MRR) was assessed. In addition, patients were divided into 3 groups to test for differences based on age quartiles (≤52 years [24.9%], 53-64 years [49.2%], ≥65 years [25.9%]). RESULTS: The mean age was 59±9 years with a range from 22 to 79 years. The mean resting Q (Q(rest)) was not different in the 3 age groups (88±34 mL/min, 82±29 mL/min, and 86±38 mL/min, R(2)=0.001; p=0.62). A trend towards a decreasing mean hyperaemic Q (Q(max)) was observed with increasing age (223±79 mL/min, 209±84 mL/min, 200±80 mL/min, R(2)=0.010; p=0.083). The mean resting R(μ) (R(μ,rest)) were 1,204±460 Wood units (WU), 1,260±411 WU, and 1,289±455 WU (p=0.23). The mean hyperaemic R(μ) (R(μ,hyp)) increased significantly with advancing age (429±149 WU, 464±164 WU, 503±162 WU, R(2)=0.026; p=0.005). Consequently, MRR decreased with age (3.2±1.2, 3.1±1.0, 2.9±0.9; p=0.038). This trend was present in both the patients with (n=121) and without (n=184) coronary microvascular dysfunction (CMD). CONCLUSIONS: There is an age-dependent physiological increase in minimal microvascular resistance and decrease in microvascular function, which is represented by a decreased MRR and is independent of atherosclerosis. The age-dependent decrease in MRR was present in both patients with and without CMD and was most evident in patients with smooth coronary arteries.