This is a prospective, single center study involving 150 patients with stable coronary artery disease undergoing coronary angiography for chest pain evaluation. The relationship between FFR values and inducible myocardial ischemia at the time of definite ischemia during adenosine stress testing will be investigated.

Fractional flow reserve (FFR) is commonly used to search for ischemia-producing lesions during percutaneous coronary intervention (PCI), and its assessment becomes an integral part to guide PCI when objective evidences of inducible myocardial ischemia are not available. A transient imbalance between oxygen supply and demand leads to the ischemic cascade, which are typically accompanied by regional wall motion abnormalities or electrocardiographic changes as objective evidences of inducible myocardial ischemia.

FFR is a pressure-derived surrogate of coronary flow limitation defined as the ratio of distal coronary pressure to aortic pressure during maximal hyperemia. FFR has been indirectly validated against noninvasive stress tests, and large outcome trials support the benefit of FFR-guided PCI strategy. However, FFR is not a direct measurement of coronary flow, and myocardial ischemia depends on coronary flow rather than pressure. In fact, an experimental model shows that myocardial function can be maintained without evidences of myocardial ischemia despite low FFR. Furthermore, FFR did not predict improvement in symptoms or exercise performance after PCI, challenging the current threshold of FFR for discriminating ischemia-producing lesions.

The clinical benefit of FFR-guided PCI is certainly related to relief of inducible myocardial ischemia. However, there is little information to examine a direct link between FFR values and documented inducible ischemia at the time of FFR measurement. Therefore, the investigators investigate the relationship between FFR values and inducible myocardial ischemia at the time of definite ischemia during adenosine stress testing.

A 12-lead ECG recordings, FFR, and two-dimensional echocardiographic monitoring will be continued before, during and after adenosine infusion. When new regional wall motion abnormalities in echocardiography develop, adenosine infusion is ended and echocardiographic monitoring will be continued until left ventricular wall motion returns to normal. Apical (two-chamber, four-chamber and five chamber views) and parasternal long-axis and short-axis views will be recorded for offline analysis.

Inclusion Criteria:

• Men or women at least 18 years of age
• Patients undergoing coronary angiography
• Moderate to severe stenosis (diameter stenosis equal or more than 50 percent by visual examination) in one major epicardial coronary artery
• Normal left ventricular function without regional wall motion abnormality

Exclusion Criteria:

• Contraindications to adenosine stress test*
• ECG abnormalities (bundle branch block, LVH with strain, pacing rhythm, WPW)
• History of previous myocardial infarction
• Significant multi-vessel coronary artery disease (diameter stenosis equal or more than 50%)
• Hypertrophic cardiomyopathy
• Significant valvular heart disease
• Bronchial asthma or chronic obstructive lung disease
• Hepatic disease or biliary tract obstruction, or significant hepatic enzyme elevation (ALT or AST > 3 times upper limit of normal).
• Current treatment for the active cancer
• Expected life expectancy < 1 year
• Unwillingness or inability to comply with the procedures described in this protocol.