Fractional Flow Reserve (FFR) has recently emerged and has been largely validated as a safe and efficacious way of ischemia testing for patients with stable angina. The new recently ESC guidelines have strongly suggested a FFR based approach for patients with stable angina, also for those with challenging lesions like left main disease, severe multivessel stenosis for heart failure patients and those with single remaining vessels although left main disease and an ejection fraction less than 30% are exclusion criteria of the randomized controlled trials on this topic. Consequently the investigators performed a prospective multicenter study to understand the safety and efficacy of a FFR based approach for these patients.