20 Mar Instantaneous Wave-Free Ratio To Evaluate Coronary Artery Disease
MedicalResearch.com Interview with:
Matthias Götberg, MD, PhD
Director Cardiac Cath Lab
Department of Coronary Heart Disease
Skane University Hospital- Lund
MedicalResearch.com: What is the background for this study?
Response: Cardiologists encounter patients with narrowing of the coronary arteries on a daily basis. They typically use visual estimation of the severity of narrowing when performing coronary angiography, but it is difficult to accurately assess, based on a visual estimation alone, whether a stent is needed to widen the artery and allow the blood to more freely.
FFR (Fractional Flow Reserve) is more precise tool and results in better outcomes than using angiography alone to assess narrowing of the coronary arteries. With FFR, the doctor threads a thin wire through the coronary artery and measures the loss of blood pressure across the narrowed area. To acquire an accurate measurement, the patient must be given adenosine, which is a drug that dilates the blood vessels during the procedure. This drug causes discomfort; patients describe having difficulty breathing or feeling as if someone is sitting on their chest. The drug also adds to the cost of the procedure and can have other rare but serious side effects.
iFR (Instantaneous Wave-Free Ratio) is also based on coronary blood pressure measurements using a thin wire, but unlike FFR, it uses a mathematical algorithm to measure the pressure in the coronary artery only when the heart is relaxed and the coronary blood flow is high. As a result, a vasodilator drug is not needed.
iFR has been validated in smaller trials and have been found to be equally good as FFR to detect ischemia, but larger randomized outcome trials are lacking.
iFR-Swedeheart is a Scandinavian Registry-based Randomized Clinical Trial (RRCT) in which 2000 patients were randomized between iFR and FFR as strategies for performing assessment of narrowed coronary vessels. The primary composite endpoint at 12 months was all-cause death, non-fatal myocardial infarction, and unplanned revascularization.
RRCT is a new trial design originating from Scandinavia using existing web-based national quality registries for online data entry, randomization and tracking of events. This allows for a very high inclusion rate and low costs to run clinical trials while ensuring robust data quality.
MedicalResearch.com: What are the main findings?
Response: iFR was found to be non-inferior to FFR; 12-month outcome 6.1% (FFR) vs. 6.7% (iFR), p=0.007 for non-inferiority. The findings were similar among major subgroups. The rates of myocardial infarction, target-lesion revascularization, restenosis, and stent thrombosis did not differ significantly between the two groups.
A significantly higher proportion of patients in the FFR group (68.3%) than in the iFR group (3%) reported chest discomfort during the procedure; P<0.001). Moreover, significantly more lesions were evaluated in the iFR group while more lesions were found to be significant in the FFR group. Finally, the RRCT-design allowed for trial inclusion of >2000 patients in 15 sites in Scandinavia in less than 18 months. No patients were lost to follow-up.
MedicalResearch.com: What should readers take away from your report?
Response: iFR demonstrated similar outcome to FFR, but the fact that iFR doesn’t require adenosine resulted in a reduction in discomfort from the procedure. We expect a reduction in procedure-related costs, while improving patient experience as a result of implementing this new method into the cath-lab workflow. iFR has the potential to increase the use of physiologically guided assessment among patients with coronary artery disease, the majority of whom still undergo angiographic assessment of lesion severity.
I have minor lecture fees from Philips Volcano who sponsored this investigator initiated trial through an unrestricted grant
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March 18, 2017DOI: 10.1056/NEJMoa1616540
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