Subjects are patients who are planned to do percutaneous coronary intervention for coronary stenosis in the left circumflex artery without other stenosis in the left ascending artery and the right coronary artery, or a patient with normal coronary artery. Immediately after coronary angiography or percutaneous coronary intervention, the investigators will evaluate for coronary hemodynamics by distribution of wave intensity which is calcurated by coronary pressure and flow velocity with Combowire in each coronary segment. Also, they will assess coronary morphology by View It in each coronary segment.

Combowire (Volcano Therapeutics Inc., CA, USA) is a 0.014 inch pressure/Doppler sensor-tipped-guidewire which can measure coronary pressure and flow velocity.

View It (Terumo Co., Japan) is a guide catheter with intravascular ultrasound which can measure coronary morphology such as vessel diamter.

Inclusion Criteria:

• A patient who are planned to do percutaneous coronary intervention for stenosis in the left circumflex artery without any lesions in other coronary arteries
• Or a patient who is performed coronary angiography without significant stenosis lesion in 3-coronary vessel

Exclusion Criteria:

• A patient with coronary stenosis with LAD
• Hemodialysis
• Acute coronary syndrome
• Congestive heart failure
• A patient with shock vitals