Impact of ranolazine on coronary microvascular dysfunction (MICRO) study.

•Coronary microvascular dysfunction (CMVD) occurs in a heterogeneous group of patients. Type I CMVD occurs in the absence of obstructive epicardial coronary artery disease or structural heart disease.•This pilot study explored the use of ranolazine among patients with Type 1 CMVD and assessed the direct impact of ranolazine therapy on microcirculatory resistance.•Index of microcirculatory resistance (IMR) is an invasive tool used to measure global myocardial resistance.•Among the 7 patients enrolled with an abnormal IMR, treatment with ranolazine for four weeks was associated with an improvement in IMR, measures of angina severity and exercise tolerance.•Based on these data, a larger scale randomized trial would be feasible and important in addressing the need for proven targeted therapies for CMVD.