Researchers in Denmark have proposed a new approach that could spare patients with coronary artery disease from undergoing unnecessary and invasive diagnostic procedures.

Presenting their findings this month at ESC Congress 2018 in Munich, the investigators argued that utilizing fractional flow reserve computed tomography (FFRCT) rather than invasive operations like FFR can determine appropriate forms of treatment for patients. It is the first clinical study to show the benefits of FFRCT in patients with moderate stenosis.

"FFR is measured by inserting a pressure wire distal to the coronary stenosis of interest. Although generally a safe procedure, every instrumentation of the coronaries may be a risk - dissection, perforation, myocardial infaction, stroke, bleeding," Dr Bjarne Linde Nørgaard, principal investigator of Aarhus University Hospital in Denmark, told HCB News. "CT-FFR is based on standard acquired datasets (no extra imaging, radiation, medication), and thus is not associated with any additional risk."

Current practice requires patients to undergo noninvasive computed tomography angiography to determine the degree of stenosis, followed by an invasive FFR assessment to evaluate whether the stenosis is causing ischemia by blocking blood flow. FFR involves inserting a pressure wire into the artery to calculate the ratio between the maximum blood flow in narrow arteries and the maximum blood flow in normal ones.

Applying FFRCT to 3,674 patients with stable angina, researchers assessed ischaemia by calculating FRR using anatomic information from standard coronary CTA scans and an algorithm for simulating blood flow. All patients previously underwent coronary CTA after incurring new onset chest pain between 2014 and 2016.

The approach determined that 677 suffered from moderate stenosis, requiring FFRCT to oversee further management. Of this number, 410 were found to have normal FFRCT and were treated with drugs alone, requiring no referral for coronary angiography or other invasive testing.

A total of 2,540 patients had mild stenosis and received no additional testing while 0.80 percent or less were diagnosed with abnormal FFRCT and subjected to either medical therapy alone or invasive coronary angiography, depending on the number of affected arteries and their locations.

Researchers then evaluated the onset of a combined endpoint of all-cause death, myocardial infarction, hospitalization rates for unstable angina and unplanned revascularization between patients with mild stenosis on coronary CTA and those with moderate stenosis on coronary CTA but normal FFRCT, finding little difference between the two at 2.8 percent and 3.9 percent, respectively.

The findings back several clinical trial conclusions that the use of FFRCT accurately reflects invasively-measured FFR. They also plug in gaps in understanding the clinical outcomes derived from the use of coronary CTA and FFRCT to determine treatment, an area that lacks much information.

"Surprisingly we found that some patients with a positive test result Who were not referred to cath for various reasons had a six-fold increased risk of myocardial infarction when compared to those with a positive test result who were sent to the cath lab," said Nørgaard. "We need to see that our findings can be mirrored in other centers and health care systems through multicenter prospective studies. We also need to learn more in future studies on how to best interpret a positive CT-FFR result, and how to best manage such patients."

Such multicenter prospective studies are ongoing, one of which is a large multinational, clinical practice CT-FFR registry of 5,000 patients. Data from this trial is set to be published in early 2019. Large scale randomized trials investigating the prognostic value of CT-FFR against conventional ischemia testing like SPECT and stress echo are also in pipeline.

Data for this study was supplied by the Western Denmark Cardiac Computed Tomography (WDCT) Registry, the Danish National Patient Registry, and the Civil Registration System.

The findings were published in the Journal of the American College of Cardiology.