Little is known about the hyperemic efficacy of IV adenosine as well as safety in patients with heart failure with reduced ejection fraction (HFrEF) because they were excluded from the major FFR studies. We will evaluate the feasibility and hyperemic efficacy of IV adenosine in patients with HFrEF in comparison with IC nicorandil for invasive physiological assessment using a coronary pressure wire. Patients with an angiographically intermediate lesion (40-70% diameter stenosis) in a major epicardial coronary artery and with left ventricle ejection fraction ≤40% will be prospectively enrolled. FFR under the various hyperemic stimulation using IV adenosine 140 \& 180, IC adenosine, and IC nicorandil will be measured sequentially.
