PET may be beneficial to guide revascularization strategy for CAD
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PET perfusion and flow assessment may guide revascularization strategies for patients with CAD, according to a presentation at the Scientific Session and Exhibition of the American Society of Nuclear Cardiology.
“Over the past decade, interventional cardiologists have moved away from assessing coronary stenoses from an anatomical standpoint to a physiologic standpoint,” Timothy M. Bateman, MD, MASNC, co-director of cardiovascular radiologic imaging at Mid-America Heart Institute and the Saint Luke’s Health System in Kansas City and professor of medicine at University of Missouri – Kansas City, said during the presentation. “Data from the FAME 1 and FAME 2 trials showed that physiological assessments led to fewer cardiac events and improved quality of life. The ISCHEMIA trial had similar results, showing that interventions benefitted symptomatic patients.”
Despite these findings, a question persists over whether good decisions can be made regarding benefit in patients sent to the catheterization laboratory for an interventional procedure based on results from myocardial perfusion PET.
“PET offers a lot of information that we historically have not been able to get from a spatially relative perfusion defect analysis typically provided by a SPECT study,” Bateman said during the presentation.
Bateman added that PET images are of high quality and that they are all attenuation-corrected. Results are obtained quickly, which allow clinicians to analyze a true rest and peak stress functional assessments including ejection fraction and systolic volume, regional wall thickening and regional wall motion, Hybrid instrumentation can also be used to assess the presence of and quantify coronary artery calcium. Myocardial blood flow can also be assessed through PET at rest and at the peak of stress.
PET may correlate with invasive physiologic measurements like flow measurements, for example.
“It may tell us that we can do these types of quantitative flow measurements and get a good estimate of what has occurred,” Bateman said during the presentation.
With regards to risk stratification, in patients with normal blood flow reserve and normal PET scans, the prevalence of events is very low and event-free survival is high, according to the presentation. In contrast, cardiac event-free survival over time can significantly differ in patients with abnormal flow reserve.
“Myocardial blood flow reserve predicts cardiac mortality even in patients without perfusion defects,” Bateman said during the presentation.
PET may also play a role in determining CAD risk, as normal myocardial blood flow reserve excludes high-risk coronary disease, according to the presentation.
“It contributes majorly with respect to risk assessment,” Bateman said during the presentation. “We place a lot of importance on flow reserve, but sometimes we need to also look closely at peak blood flow dependent upon a number of factors on what’s going on with blood pressure, heart rate and other factors at risk.”
Researchers in a study published in the European Heart Journal in 2019 substratified patients by myocardial blood flow reserve and found that the percentage of ischemia correlated with outcomes. Patients with higher percentages of ischemia had worse survival rates. Researchers also found that myocardial blood flow reserve had a major impact on outcomes.
“In fact, it’s interesting that when myocardial blood flow reserve is above 1.8, the survival is almost the same regardless of whether people have no ischemia or more than 10% ischemia,” Bateman said during the presentation.
PET might also be able to guide management decisions. A study published in the Journal of the American College of Cardiology in 2019 found that patients with low-risk PET scans had lower rates of angiography and revascularization and patients with high-risk PET scans had higher rates of these interventions compared with AC SPECT scans.
PET may also predict a survival benefit from revascularization compared with medical management. Patients with myocardial blood flow reserve less than 1.8 often do better with revascularization compared with medical therapy independent of the percentage of ischemia or scar, EF, EF reserve, calcium, sex and age, according to the same study published in the Journal of the American College of Cardiology.
PET may also predict improvements in quality of life from revascularization, as patients with greater degrees of ischemia had better quality of life after revascularization, according to the study in the Journal of the American College of Cardiology.
“We have a powerful test,” Bateman said during the presentation. “It provides a large amount of data relative to decision making about revascularization. Blood flow quantification is really central to its performance in this arena. Publications appear promising that it can indeed guide revascularization decisions, and the focus has been on both hard outcomes and quality of life.”
References:
- De Bruyne B, et al. N Engl J Med. 2012;doi:10.1056/nejmoa1205361.
- Fearon WF, et al. Circulation. 2017;doi:10.1161/CIRCULATIONAHA.117.031907.
- Patel KK, et al. Eur Heart J. 2019;doi:10.1093/eurheartj/ehz389.
- Patel KK, et al. J Am Coll Cardiol. 2019;doi:10.1016/j.jacc.2019.07.055.
- Spertus JA, et al. N Engl J Med. 2020;doi:10.1056/NEJMoa1916370.
- Ziadi MC, et al. J Am Coll Cardiol. 2011;doi:10.1016/j.jacc.2011.01.065.
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Bateman TM. Clinical PET in CAD. Presented at: Scientific Session and Exhibition of the American Society of Nuclear Cardiology; Sept. 25-26, 2020 (virtual meeting).
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