According to a study published in Radiology, cardiac hybrid imaging with computed tomography (CT) and nuclear stress testing is an excellent long-term predictor of adverse cardiac events such as myocardial infarction in patients being evaluated for coronary artery disease.
Philipp A Kaufmann (University Hospital Zurich, Zurich, Switzerland) and colleagues looked at 428 patients who underwent hybrid imaging. During a median follow-up of 6.8 years, a total of 160 major adverse cardiac events—including 45 deaths—were observed in the final study population. Patients with matched findings (stenosis of 50% or more on CT angiogram with evidence of ischaemia on single photon emission tomography [SPECT] in the area of the heart to which the blocked vessel was supplying blood) had more than five times the risk of adverse events than those with normal findings. Patients with unmatched findings, or evidence of ischaemia but not in the area of the heart being fed by the stenotic artery, had three times the risk. Major adverse cardiac event rates were 21.8% for matched findings and 9% for unmatched—considerably higher than the 2.4% rate for normal findings.
The results show that cardiac hybrid imaging is an excellent long-term predictor of adverse cardiac events in patients evaluated for coronary artery disease. Kaufmann says that hybrid imaging findings could help guide treatment decisions, such as whether or not a patient should have a revascularisation procedure such as bypass or angioplasty. He comments: “In patients with multiple lesions or complex coronary anatomy, it is, in many cases, very difficult to correctly identify the culprit lesion. In a previous multicentre trial with hybrid imaging we were able to see that about one in five patients should be revascularised in another coronary artery than originally planned. The present study now documents the prognostic importance of the comprehensive assessment provided by hybrid imaging.”
The study supports CT angiography use for an initial, non-invasive evaluation of patients with known or suspected stable coronary artery disease. No additional imaging would be necessary if the results were normal. If a lesion was evident, then clinicians could employ a nuclear scan to assess ischaemia and take advantage of both modalities by fusing the results together to make a hybrid image.
“The strategy of direct referral to invasive coronary angiography without non-invasive imaging is obsolete. Even after documenting coronary artery disease with CT angiography, we need further non-invasive evaluation before deciding upon revascularization versus medication,” Kaufmann notes.
Kaufmann et al hope to run a trial to show that hybrid imaging can have a positive impact on patient outcomes. They are also looking at what they call “triple hybrid” imaging, which combines the CT angiography/SPECT hybrid with information on coronary artery shear stress. The shear stress information could help identify lesions that do not yet have an impact on ischaemia but will in the future.