It Is known from several studies that coronary microvascular dysfunction (CMD) is an independent predictor of future adverse cardiovascular events in healthy volunteers, patients with non-obstructive coronary artery disease (CAD), and patients with ST-elevation myocardial infarction. However, the relationship between aortic stiffness and coronary microvascular dysfunction (CMD) remains unclear. This study from Japan by T. Muroya et al. (Sasebo City General Hospital, Japan) aimed to determine whether aortic stiffness causes CMD as evaluated by the hyperaemic microvascular resistance index in patients with non-obstructive Coronary Artery Disease (CAD). A multivariate regression analysis identified that aortic stiffness may cause CMD in patients with non-obstructive CAD via increased coronary microvascular resistance. Take-home message: aortic stiffness is associated with CMD which is evaluated as hyperaemic microvascular resistance in patients with non-obstructive CAD. The main limitations of this study are that it involved a small study population and was performed at a single facility.