BACKGROUND: The iPOWER study aims at determining whether routine assessment of coronary microvascular dysfunction (CMD) in women with angina and no obstructive coronary artery disease is feasible and identifies women at risk.

METHODS: All women with angina referred to invasive angiographic assessment in Eastern Denmark are invited to join the study according to in- and exclusion criteria. Assessment includes demographic, clinical and psychosocial data, symptoms, electrocardiogram, blood- and urine samples and transthoracic echocardiography during rest and dipyridamol stress with measurement of coronary flow reserve (CFR) by Doppler of the left anterior descending artery. In substudies CMD will be assessed by positron emission tomography, peripheral endothelial function, magnetic resonance imaging-and computed tomography derived myocardial perfusion scans, angiographic corrected TIMI frame counts, advanced echocardiographic modalities at rest and during stress, and invasive measures of CFR and coronary vascular reactivity. The study will include 2000 women who will be followed for 5 years for cardiovascular outcomes.

RESULTS: By May 2013, 1685 women have been screened, 759 eligible patients identified, 530 contacted, and 299 (56%) agreed to participate. Among the first 50 patients, Doppler CFR was successfully measured in 49 (98%).

CONCLUSIONS: Among women with suspected ischemic heart disease and no obstructive coronary artery disease, non-invasive Doppler CFR is feasible as a routine assessment. The study will provide information on methods to diagnose CMD and determine the prognostic value of routine non-invasive assessment of microvascular function. Future study will provide women identified with CMD participation in interventional substudies designed to test treatment strategies.