Obstructive Coronary Artery Disease

* Chest pain is one of the most common symptoms of heart disease. This could be due to narrowing in heart's blood vessels, which needs to be investigated. * Currently, people with a low risk of narrowing of heart vessels usually have a CT scan of the heart first. This scan is good at identifying those who do not have significant narrowing. However, the scan has some drawbacks, such as exposure to a small amount of radiation. * We are exploring if ultrasound of the neck vessels might give us similar kind of information as the CT scan. * You will be asked to attend the hospital for one visit to have an ultrasound scan of your neck. * The findings of your neck vessels will be compared with the CT scan of your heart vessels to see if there is a similarity.

The goal of this clinical trial is to test whether adding coronary function testing and starting targeted medical treatment for identified vasomotor disorders will also improve angina symptoms and quality of life in patients with obstructive coronary artery disease who undergo percutaneous coronary intervention. The main question it aims to answer is: Does performing coronary function testing in patients with obstructive coronary artery disease who undergo percutaneous coronary intervention lead to better relieve of angina symptoms and improvement in quality of life? Researchers will compare this group undergoing coronary function testing with a control group who will solely undergo percutaneous coronary intervention. Participants will: * Undergo percutaneous coronary intervention and coronary function testing in the intervention arm * Undergo percutaneous coronary intervention in the control arm

Murray-law based single-view quantitative flow ratio (µQFR) has been recommended for guiding percutaneous coronary intervention (PCI) in selective patients. However, it's reliability has not been validated in bifurcation lesions which present complex anatomy and flluid conditions before and after PCI. The goal of this study is to investigate the diagnostic performance of µQFR in side branch after single-stent treatment for bifurcation lesions in patient with obstructive coronary artery diseases.