Do we have the COURAGE to stop using percentage stenosis?
It has been a year since my first blog and in honor of this occasion; I have decided to pose a controversial question. The 2-year follow-up data from the FAME (Fractional Flow Reserve versus Angiography for Multi-vessel Evaluation) trial [1] shows that patients with coronary artery disease undergoing PCI guided by pressure-wire have significantly fewer adverse events. Moreover, the event-free survival benefits are greater than patients undergoing revascularization based on angiographic stenosis alone. These results confirm the findings from the original FAME study.[2]
Historically, large revascularization trials have compared PCI with medical therapy on the basis of angiographic stenosis.[3] However, we know that stenosis severity is a poor relation of FFR and coronary flow reserve.[4–6]. This is due to a number of factors such as: the heterogeneity of diffuse disease; sequential stenoses; arterial remodelling and endothelial dysfunction, which all dynamically alter the real severity of a stenosis. In a paper by Tonino et al evaluating patients with a visually estimated 50-70% diameter stenosis on angiography, only 35% had ischaemic FFR measurements[7] Furthermore, 1 in 5 of 71–90% diameter stenoses had an FFR indicating no substantial ischaemia [7] This data confirms that coronary angiography is not able to provide us with a lot of the information required to judge the true severity of ischemia. This needs to be taken seriously, as it forms the basis for decisions about many revascularization procedures around the world.
It seems clear to me that one of the many reasons why PCI has failed to dramatically improve event rates and survival (in previous studies) is the continued use of percentage stenosis to guide therapy. This can systematically fail to correctly identify patients with limited coronary flow, who would benefit from a procedure and many other patients will unfortunately undergo a procedure, when there is no significant problem!
In summary, I feel that all the previous research and debate into the question of which is better: “intervention or medical treatment” is flawed in this contemporary environment, due to incorrect patient selection. However, a subgroup analysis of the COURAGE trial [8] has shown that the risk of death or MI rises and falls in tandem with the extent of residual ischemic myocardium at follow-up imaging. When comparing 231 patients with a small reduction in ischaemia, the 82 with an ischaemia reduction >5% of myocardium had a 0.47 relative risk of death or MI (95% CI 0.23-0.95, p=0.037).
So, what is the potential solution to this fundamental flaw? The first step appears obvious, measure FFR (if possible) at the time of lesion assessment and use the FFR to guide the decisions, not the angiogram. If you have a fantastic non-invasive service you may have access to robust stress echocardiography or nuclear techniques, such as PET or SPECT that can inform and complement your decision making, before risking an intervention or even a wire.
Do you agree or disagree? Please comment or get involved in the debate, I hope that controversial discussion will inform us all about the right thing to do for our patients.
Best wishes for spring 2011.
Dr Scott W Murray BSc (Hons) MB ChB MRCP
Biography
Scott Murray is currently employed as a Specialist Registrar in Cardiology at The Liverpool Heart and Chest Hospital NHS Foundation Trust, U.K. His main interest is coronary intervention and atherosclerosis imaging and he is currently P.I for an observation study using Intravascular Ultrasound: The Liverpool V-HEART study – Virtual Histology Evaluation of ACS Requiring Treatment. He hopes to provide the journal with a light-flavour of Cardiology musings from across the pond.
Scott Murray grew up in a small steel town in Scotland called Wishaw. He attended Glasgow University Medical School, where he gained not only his medical degree but also a degree in sports and exercise medicine. Cardiology became a focus early in his studies and he has taken this into his medical career. He is currently employed as a Specialist Registrar in Cardiology at The Liverpool Heart and Chest Hospital NHS Foundation Trust, U.K. His main interest is coronary intervention and atherosclerosis imaging and he is currently P.I for an observation study using Intravascular Ultrasound: The Liverpool V-HEART study – Virtual Histology Evaluation of ACS Requiring Treatment. He hopes to provide the journal
