Research Projects
FLASH - Fractional Flow Reserve Hong Kong

Programme(s) to which this project applies:

☒ MPhil/PhD ☑ MRes[Med] ☒ URIS

The presence of inducible myocardial ischemia is the prerequisite indication for percutaneous coronary intervention (PCI). Coronary physiology is an important tool that can guide management decisions for intermediate lesions and multivessel coronary artery disease (CAD), determining whether the patient would benefit from revascularization or medical therapy. In this regard, a pressure-derived physiologic index, fractional flow reserve (FFR), has been the standard invasive method to evaluate the functional significance of epicardial coronary artery stenosis. FFR is defined as the ratio of mean distal coronary pressure to mean aortic pressure (FFR=P_d/P_a ). Fractional flow reserve (FFR) utilizes a specialized guide wire to measure blood pressure within a coronary artery.1, 2 The original description of FFR required the induction of maximal hyperaemia to achieve near linear correlation between coronary pressure and blood flow. The most commonly used pharmacological agent is adenosine as an intravenous infusion, although recent evidence suggests that high-dose intracoronary bolus injection may have similar efficacy (200 mcg into the left coronary artery and 100 mcg in the right coronary artery). Incorporating stenosis severity, myocardial territory and viability, and collateral perfusion, FFR is able to fully assess the functional significance of a coronary stenosis. (Diagnostic Agreement of Quantitative Flow Ratio With Fractional Flow Reserve and Instantaneous Wave‐Free Ratio)

Recently, instantaneous wave-free ratio (iFR), which does not require hyperaemia, was developed as an alternative for FFR, 3 and 2 randomized controlled trials demonstrated comparable clinical outcomes between iFR and FFR guided strategies with less use of revascularization after iFR-guided treatment. On this ground, recent guidelines recommend the measurement of FFR or iFR in defining the functional significance of intermediate epicardial coronary stenosis as a class IA recommendation.

However, the adoption rates of FFR or iFR guided percutaneous coronary intervention are still low in real-world practice. The use remains significantly underutilized in practice, with FFR being used in 6.1% of interventions for intermediate coronary lesions (40-70% stenosis). As alternative methods to evaluate functional significance of epicardial coronary stenosis, functional coronary imaging has recently emerged, allowing wire-free functional assessment of stenosis severity based on a computational fluid dynamics model or mathematical assumptions of coronary flow.

In comparison with traditional measurement of FFR by inserting a pressure wire distal to the stenosis, angiography-based FFR was proposed as a new technique without using invasive pressure wire and hyperaemic stimulus.3, 4 Prospective and multicentre trials have shown higher diagnostic accuracy of angiography-based FFR (e.g., QFR and FFRangio) than non-invasive FFRCT.5-7 The mathematical formula method (i.e., QFR in the FAVOR II China Trial) and the lumped model (i.e., FFRangio in the FAST-FFR Trial) had diagnostic accuracy of ~92% for FFR values from zero to one and ~86% for FFR values between 0.75 and 0.85 by using the wire-based FFR as reference standard with a cutoff value of 0.80. FAVOR II Europe and Japan Trial and WIFI II Trial, however, showed relatively lower accuracy of QFR, particularly for FFR values between 0.75 and 0.85.8, 9 It is required to develop new approaches to further enhance online diagnostic performance of angiography-based FFR.

Professor KH Yiu, Department of Medicine

Professor Yiu received his undergraduate degree in 2001 and completed his Cardiology specialty training in 2008 at the Queen Mary Hospital. He subsequently joined the University of Hong Kong in 2011 as a Clinical Assistant Professor in Cardiology and been promoted to Clinical Associate Professor at the Department of Medicine in 2015. He has completed his Doctor of Medicine degree (HKU) in year 2012 and PhD in 2016 at the Leiden University, the Netherlands on “Clinical application of cardiac imaging: echocardiography and computed tomography”. He has prolifically published over 130 peer-review original articles in international peer-review journals. Among these, he was either first or corresponding author in 45 of them; including 9 articles with impact factors exceeding 5 (Maximum 15). In addition, Professor Yiu has acquired the clinical skills of transcatheter aortic valvular implantation (TAVI) in year 2010 in Lepzig, Germany and had performed over 40 procedures during his stay in Leiden.

His research interest is based on the advanced imaging technique in the cardiovascular system using novel echocardiography techniques and computed tomography. By using these imaging techniques, he was able to identify subclinical cardiovascular abnormalities that improves management of patients with or at risk of cardiovascular disease. Furthermore, he has established and led three important research study projects, namely the Chinese Valvular Heart Disease study (CVATS), the Chinese Diabetic Heart Disease Study (CDATS) and the Chinese Rheumatology Heart Disease Study (CRADS). He is the first and corresponding author of 3 original articles based on the CVATS of which one of them was published in Circulation and was awarded with the “Distinguished Research Paper Award for Young Investigator 2014: Hong Kong College of Physician”. He is the first and/or corresponding author of 6 original articles and 1 review article on CDATS. In addition, he is the first and/or corresponding author over 10 original articles and 1 review article on CRADS. Based on the ground work from these 3 important study consortiums, Professor Yiu has secured 3 GRF grants and 1 HMRF grant, with a total of over 5 million HKD, in the past 5 years.

His clinical interest includes interventional cardiology (coronary and structural) and cardiac imaging. He is also leading the cardiology service in the HKUSZ-hospital and currently the deputy COS of the Department of Medicine, HKUSZ hospital.

HKU Scholars Hub

For more information or to express interest for this project, please email the supervisor or the specified contact point in the project description.  Interested candidates are advised to enclose with your email:

  1. your CV,
  2. a brief description of your research interest and experience, and
  3. two reference letters (not required for HKUMed UG students seeking MRes[Med]/URIS projects).

Information on the research programme, funding support and admission documentations could be referenced online at the Research Postgraduate Admissions website. General admission enquiries should be directed to

HKUMed MBBS students interested in the Master of Research in Medicine (MRes[Med]) programme may visit the programme website for more information.  

HKUMed UG students interested in the Undergraduate Research Internship Scheme (URIS) may visit the scheme’s website for more information.