Fractional flow reserve CT (FFR-CT) was significantly better at predicting the long-term effects of cardiac disease -- including death, heart attack, and the need for revascularization -- than conventional coronary CT angiography (CCTA) in a new study, published online June 11 in Radiology.
For the prospective study, an international team of researchers evaluated data from participants of the Analysis of Coronary Blood Flow Using CT Angiography: Next Steps (NXT) trial who underwent a CCTA scan and FFR-CT analysis for suspicion of coronary artery disease with stenosis.
Multiple groups have demonstrated that FFR-CT measurements based on information from CCTA scans can match the accuracy of invasive fractional flow reserve, the current gold standard, for detecting ischemia. Studies such as the Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) FFR-CT trial have also shown that FFR-CT can predict short-term clinical outcomes much more effectively than CCTA alone, noted lead author Dr. Abdul Ihdayhid, from Monash University in Australia, and colleagues.
However, research has yet to determine the capacity of FFR-CT to improve diagnostic yield for patients with severe stenosis over an extended period of time, Ihdayhid and colleagues continued. As a result, they set out to determine the technique's prognostic value for 206 NXT trial participants roughly five years after their initial exam. The average age of the participants was 64 years, and 64% were men.
Upon analyzing the data, the researchers found that a positive FFR-CT exam (i.e., a score of 0.8 or less) was a considerably better predictor of myocardial infarction (MI), death, revascularization procedures, and major adverse cardiac events (MACE) than a positive CCTA exam (i.e., showing stenosis of 50% or greater in at least one artery).
| CCTA vs. FFR-CT for coronary artery disease long-term outcomes | ||
| CCTA | FFR-CT | |
| Area under the curve for predicting MI, death, revascularization | 0.52 | 0.71 |
| Area under the curve for predicting MACE | 0.54 | 0.76 |
| Frequency of MI, death, revascularization for a positive exam | 48.7% | 73.4% |
| Frequency of MACE for a positive exam | 10.2% | 15.6% |
What's more, the researchers discovered that the patients' likelihood of heart attack, death, or revascularization increased by a statistically significant degree with incremental reductions in FFR-CT. To be specific, each decrease of 0.05 in FFR-CT score was independently associated with a greater incidence of adverse events.
This finding confirms the existence of a significant and independent relationship between the numeric value of FFR-CT and risk of clinical outcomes -- suggesting that FFR data may be most beneficial when interpreted on a "risk continuum" rather than in a dichotomous manner, the researchers noted.
Despite these benefits, the full implementation of FFR-CT into clinical practice faces many challenges, including a lack of widespread reimbursement and long turnaround times (currently about five hours), Drs. Carole Dennie and Fraser Rubens from the University of Ottawa in Canada wrote in an accompanying editorial.
Still, FFR-CT technology shows promise as a first-line test for assessing patients suspected of requiring intervention for coronary artery disease.
"The path forward is exciting as this opens the door for discussions on how to redefine the indications and strategies that will form the basis of tomorrow's guidelines on the treatment of coronary disease," they wrote.
