What new data, expert guidelines tell us about the future of cardiac CT

She also acknowledged the necessity of a patient-centric approach in imaging, where the choice of diagnostic modality aligns with patient characteristics and institutional expertise. Some centers may not have the the training to read CTA or to technology to conduct conduct the test, for example. 

Trial insights unveil CTA's role in cardiac diagnosis

She said the top trials include DANCAVAS, ROBINSCA and PRECISE,[1-3] showcasing breakthroughs in CTA utilization. Among these, the PRECISE trial stood out, revealing how CT-derived fractional flow reserve (FFR-CT) enhances the accuracy of CTA diagnoses while reducing unnecessary catheterizations.

"I was really impressed by the PRECISE trial, because the study findings had shown that using FFR-CT was able to reduce the number of false positives and false negative scans. Also, it increased the yield of diagnostic cardiac catheterizations, where most of the patients that were sent to the lab for cardiac catheterization were found to have obstructed disease and then went on to get vascularized," Bullock-Palmer explained.

The DANCAVAS and ROBINSCA trials explored the prognostic potential of coronary calcium scorings. DANCAVAS highlighted mortality prediction solely in men under 70, while ROBINSCA showcased the precision of calcium scoring in risk stratification, enabling targeted preventive strategies.

Comparison of CTA guidelines and challenges

Bullock-Palmer said the 2021 ACC/AHA chest pain guidelines,[4] ESC guidelines for chronic coronary artery disease,[5] and NICE guidelines[6] are all comparable, but not necessarily identical. While ACC/AHA and ESC guidelines emphasize risk factor profiles for tailored testing, for instance, NICE diverges by prioritizing anatomical testing via CT. These varying viewpoints fostered a robust panel discussion, emphasizing the need for pragmatic yet evidence-based guidelines.

However, translating guidelines into clinical practice poses challenges, notably in resource-constrained settings. Disparities in CT scanner availability, especially in rural or underserved areas, hinder the uniform implementation of recommended strategies. This issue became very evident in 2016, when the U.K. NICE guidelines recommended coronary CTA (CCTA) as a front-line imaging test for chest pain, but it quickly became apparent the country needed to ramp up its CCTA program to meet demand.

"The NICE guidelines did show that there was a shortage of available CT readers and also CT as a modality for some of these institutions," Bullock-Palmer explained.

Real-world challenges and future prospects for CCTA

The scarcity of CT scanners in certain regions, compounded by limitations in interpreting specific cases (e.g., high BMI or post-surgical patients), underscores the need for a diverse modality testing approach. Integrating functional testing alongside CTA becomes imperative in scenarios where CTA might not be feasible or optimal.

"I think a patient-first strategy is best because rather than a modality for a strategy. And not every patient can get a CT, of course. I mean there are challenges for CT in terms of patients with high body mass index (BMI), or if they have had a stent, because not everyone has a photon-counting CT scanner that can image stents beautifully. If they have had bypass grafts, there are certain challenges. So in those patients, I tend to do a functional testing strategy. Of course, if you have PET imaging, then that is really ideal because then you can look at microvascular coronary artery disease," Bullock-Palmer said.

As CCTA continued rapid growth in the U.S. due to the 2021 chest pain guidelines, one of the biggest limiting issues is expertise to read the exams and access to cardiac-capable CT systems. 

"There are challenges that each institution may have, different from another institution, in terms of the modalities available and the expertise. That is very important, because it is no use getting a CT if it is not going to be interpreted correctly," she explained. 

Addressing these concerns requires involvement of various stakeholders—clinicians, radiologists, cardiologists and management of healthcare institutions. 

Real-world applicability of FFR-CT

The 2021 chest pain guidelines recommended use of FFR-CT to better assess patients non-invasively with CT. However, at the time of the guideline release there was controversy when some notable cardiac imagers and the American Society of Nuclear cardiology said the recommendation was premature because there was not enough clinical evidence. The large PRECISE trial delivered the additional clinical evidence that clearly showed FFR-CT improved patient outcomes.

Despite that evidence, there is still debate about including FFR-CT in the guidelines because few hospitals actually have access to the technology, and at the time of the guideline release, only one vendor, HeartFlow, offered it. Bullock-Palmer said that, as new FFR-CT vendors enter the market, it will open up opportunities for broader adaptation of that technology. At the 2023 SCCT meeting, there were at least three new vendors showing their own versions of FFR-CT technologies in their booths.

Another barrier to wander adoption of FFR-CT is the time it takes to get results back; it usually taking at least a couple hours, or even a day. 

"I think that the turnaround time is something that needs to be addressed. The ideal situation would be to have a point-of-care analysis at the time in which you are reading these patients. Of course you can't do an CT-FFR for an ER patient when you really want to get your answer right now to make sure that you don't have to admit that patient unnecessarily or even observe that patient for 24 hours unnecessarily. 

Along with PRECISE, she said other trials to come will further increased validation of FFR-CT. Adding multiple players in the space and then being able to have a quicker turnaround times will also be key to wider expansion of FFT-CT.