CT perfusion imaging predicts adverse events for patients with CAD
A quantification of myocardial blood flow using CT perfusion (CTP) imaging was strongly predictive of major adverse cardiac events (MACE) and offered additional prognostic ability when added to coronary CT angiography, researchers reported in JACC: Cardiovascular Imaging.
Satoshi Nakamura, MD, and colleagues studied 332 patients at a single Japanese center who had suspected coronary artery disease (CAD) and underwent both CT angiography (CTA) and dynamic CTP. They analyzed 16 myocardial segments and used a summed stress score based on the severity of myocardial blood flow issues, if any, noted in each segment. Segments were scored from 0 to 4 for normal to most restricted flow, and abnormal perfusion was defined as a combined total of 4 or higher.
After a median follow-up of 2.5 years, 19 patients experienced a MACE, defined as cardiac death, myocardial infarction, unstable angina or hospitalization for congestive heart failure. Abnormal perfusion was the strongest independent predictor of MACEs, with individuals demonstrating that characteristic at 8.9-fold odds of having an event. Even upon multivariable adjustment—when obstructive CAD upon CTA was included—abnormal perfusion was associated with a hazard ratio of 5.7.
Annual MACE rates were 12.2 percent for patients with at least 50 percent stenosis on CTA and abnormal perfusion calculated by CTP. But when obstructive CAD was present in the setting of normal blood flow, event rates were only 1.5 percent.
“To our knowledge, this is the first study to evaluate the incremental prognostic value of MBF (myocardial blood flow) quantified with dynamic CTP in patients with suspected CAD,” Nakamura et al. wrote. “The main findings of our study were that dynamic CTP had an incremental prognostic value over CTA and that abnormal perfusion was associated with worse prognosis among those who had obstructive CAD.”
The authors believe the CTP approach could prove advantageous to fractional flow reserve (FFR) calculated from CTA.
“The evaluation of ischemia on CTP images is not influenced by coronary calcification, whereas heavy coronary calcification may affect the hemodynamic assessment of stenosis with FFRCT," they wrote. "Furthermore, FFRCT may be hampered by higher testing costs in the absence of on-site application.”
But in an accompanying editorial, two cardiologists from the University of Ottawa Heart Institute in Canada pointed out most research of CT cardiac ischemia has focused on the FFR method. They said greater industry financing devoted to FFR and concerns over increased table time (including a washout period for the contrast agent) and radiation dosage have hampered the uptake of CTP imaging.
“For CT perfusion to be accepted longer term, there needs to be much more work done on harmonization of protocols and prospective multisite multivendor comparisons of static versus dynamic CTP methods—with a primary focus on diagnosis and a (still important but) secondary focus on prognosis,” Andrew M. Crean, BM, and Benjamin J.W. Chow, MD, wrote. “We want and need CT perfusion, but whether ultimately it will prove to be a flirtation or a lasting love affair remains to be resolved.”
Daniel joined TriMed’s Chicago editorial team in 2017 as a Cardiovascular Business writer. He previously worked as a writer for daily newspapers in North Dakota and Indiana.