She added that some CCTA experts have told her that cardiac CT use has increased and it has becoming a higher priority since the guidelines were published. Some SCCT attendees she spoke with told her their hospitals were buying new CT scanners to keep up with the growing demand. Gulati said hospitals and cardiology practices are now seeing CT as a viable investment because reimbursement is becoming much easier with support from the guidelines. 

Gulati said the cost effectiveness and noninvasive nature of CCTA compared to other tests also make it attractive. 

"We are seeing some hospitals asking that CCTA be the test of choice, because of the cost and because of the fact that they can get the answers they need quickly. There are a lot of things that add to hospital costs and length of stay, but CCTA actually helps reduce a lot of that," Gulati explained.

CCTA has been used routinely in several European countries for years as a frontline test for chest pain. Gulati said Europe is ahead in this regard because it led to lower percentages of normal patients being sent to the cath lab for diagnostic angiograms than in the United States. 

Need for more of a multimodality mentality in diagnostic cardiology

Years ago, the only Class 1A recommendation for evaluating chest pain was the exercise stress ECG, and everything else was Class 2, Gulati explained. But as more clinical study evidence was built over the years to show clear diagnostic value, all the imaging modalities were elevated to Class 1A recommendations. Today, she said exercise ECG is now "lower on the totem pole" as a Class 2A recommendation for testing because the imaging provides more prognostic value for stable chest pain.  

"I think a multimodality imaging mentality is what we need to have when we are deciding what test is needed for the patient in front of us. When we have all these imaging modalities, we should be using the right test for the right patient, and obviously for different patients there are different questions. But having CT as a tool we can use I think is really important. These guidelines have made it harder for people to push back and say you don't need this test," Gulati explained. 

As a preventive cardiologist and not a cardiac imager, Gulati said she was chosen to lead the guideline writing group in part to be a neutral party when helping decide the rolls of the various imaging modalities. She said they allowed the clinical evidence and what resulted in the best outcomes for patients to decide what class of evidence a modality received and what role it should play in the guidelines. 

Inclusion of FFR-CT in the chest pain guidelines

There was some controversy over the inclusion of fractional flow reserve CT (FFR-CT) in the 2021 chest pain guidelines. Critics argued it is a new technology that still needs additional evidence and there is limited access to the technology. It was also the first artificial intelligence algorithm to be included in any U.S. cardiology guidelines. 

Gulati admits there is a need for more evidence, but the data collected so far showed a clear benefit in non invasively assessing coronary blood flow. If anatomical imaging with CT shows plaque in a coronary, the FFR-CT can determine if it is flow limiting or not and avoid sending a patient to the cath lab to determine this with invasive FFR wires placed in the arteries.  

The American Society of Nuclear Cardiology (ASNC) was the biggest critic of the guidelines and including FFR-CT because of the lack of large randomized trial data. That data actually came a year after the guidelines were released with the PRECISE trial data presented at the American Heart Association (AHA) 2022 meeting. 

PRECISE included more than 2,000 adult patients who presented with stable chest pain and suspected CAD. Patients were evaluated in one of two ways: with a strategy focused on CCTA and FFR-CT or a more traditional strategy focused on stress testing and invasive coronary angiography (ICA). Overall, the use of CCTA and FFR-CT was associated with three key benefits compared to stress testing and ICA: improved accuracy, fewer unnecessary tests and increased confidence. Risk scores determined that 20% of patients faced a minimal risk of heart disease, and nearly two-thirds of those patients did not require any follow-up testing. 

"I think FFR-CT is incredibly useful and we use it clinically. I am always asking for that additional information when it's appropriate. Avoiding the use of invasive angiography can be a huge benefit to our patients," she explained. 

Gulati said while more evidence is needed for FFR-CT, the same is true for older imaging modalities. She said the newer technologies were held to higher standards than the older modalities. She suggests there need to be large randomized trials comparing the older technologies to the newer technologies to better evaluate strengths and weaknesses and determine which tests have the best outcomes for patients and make the most economic sense.