Gender-related differences in absolute coronary flow and microvascular resistance in patients with angina and non-obstructed coronary arteries (ANOCA)

Background Women with angina more often have non-obstructive coronary artery disease (ANOCA) compared to males. Coronary microvascular dysfunction (CMD) is responsible for angina in a sizable proportion of ANOCA patients. Intracoronary continuous thermodilution allows direct quantification of absolute coronary flow (Q) and microvascular resistance (Rµ). Purpose To evaluate gender-related differences in the prevalence and pattern of CMD assessed with intracoronary continuous thermodilution in ANOCA patients. Specifically, we assessed resting and hyperemic Q (Qrest and Qhyper), R (Rµ,rest and Rµ,hyper), coronary flow reverse (CFR), and microvascular resistance reserve (MRR) in ANOCA patients stratified by gender. Methods Single-center, prospective study of patients with ANOCA. CMD was invasively assessed by intracoronary continuous thermodilution in the left anterior descending artery (LAD) and defined as CFR<2.5. Results A total of 118 patients (n=49 females and n= 69 males) were enrolled. The mean patient age was 65 years. The mean fractional flow reserve (FFR) was 0.85±0.04, with no difference between the 2 genders. There was no difference in Rµ,rest, Qrest and Qhyper between the two genders. However, Rµ,hyper were higher in females compared to males (p=0.003). Among patients with ANOCA, CMD was more prevalent in females (28% vs 22%, p=0.014). Yet, in both females and males with CMD, a higher Qrest was observed compared to patients without CMD. In male patients, also Qhyper was lower in CMD patients versus those without CMD. Conclusion Among patients with ANOCA and investigated with intracoronary continuous thermodilution, CMD appeared more prevalent in females compared to males. Females had higher microvascular Rµ,hyper compared to males. In both genders, CMD was characterized by higher Qrest, suggestive of functional rather than structural CMD.