American Society of Nuclear Cardiology (ASNC) President Dennis Calnon, M.D., MASNC, FASE, FSCCT, director of cardiac imaging for McConnell Heart Hospital at Riverside Methodist Hospital, and director of nuclear imaging for Ohio Health Heart and Vascular Physicians in Columbus, explains why the society did not endorse the first-ever U.S. or international guideline for the evaluation and diagnosis of patients with acute or stable chest pain.
Nuclear myocardial perfusion imaging (MPI) has been a gold-standard for evaluation of coronary disease in patients for years, and it is included in the new guidelines. However, computed tomography angiography (CTA) has seen immense growth over the past decade and gained a prominent position in the guidelines as a front line imaging modality. This is due to nearly all hospital emergency rooms now having access to CT systems capable of performing immediate cardiac exams. CT has been seen mainly as an anatomical imaging test, but it also can be used for myocardial perfusion imaging using iodine contrast. While CT has had limits with its ability to image through heavily calcified vessels or stents, that is changing with new CT technologies now coming into service.
One new CT technology that is prominently included I the new chest pain guidelines is CT fractional flow reserve (FFR-CT) imaging. This uses a computational fluid dynamics algorithm to analyze a patient's CTA. It sends back a report and an interactive 3D reconstruction of all the coronary vessels that shows a color coded drop in FFR ratios, which is a measure of blood flow. Past a certain threshold, the reduced flow needs to be treated with revascularization. Lower level blockages can be treated with drug therapies. FFR-CT is widely expected in the coming years to become a gate keeper for invasive diagnostic angiograms. The hope is it will eliminate the need for the majority of cath lab angiogram exams and only send patients to the lab that need a stent or angioplasty.
However, the ASNC had major issues with FFR-CT being included in the chest pain guidelines. Its board members argued there is need for more evidence and there should have been more information contraindications for its use, which was included on other imaging modalities in the guidelines. They also argued access to the technology has been very limited. Calnon explains more detail in the video on why this was a sticking point and caused the ASNC to not endorse the guidelines.
Read more in the article — First International Chest Pain Diagnosis Guidelines Released