Late sodium channel blockade improves angina and myocardial perfusion in patients with severe coronary microvascular dysfunction: Women's Ischemia Syndrome Evaluation–Coronary Vascular Dysfunction ancillary study

•In a prior trial in patients without obstructive CAD and with limited MPRI, ranolazine did not improve symptoms.•We describe myocardial perfusion response in a CFR-assessed subgroup.•Symptomatic patients with CFR <2.5 and no obstructive CAD had improved angina and myocardial perfusion with ranolazine.•The late sodium channel is important in management of coronary microvascular dysfunction.