Clinical Judgment Important When Using Imaging with DES
Sound clinical judgment, the most essential tool available to the cardiologist, is the single best method for determining the usefulness of intravascular ultrasound (IVUS) and fractional flow reserve (FFR) when using a drug-eluting stent, according to TCT Course Co-director Gary S. Mintz, MD, of the Cardiovascular Research Foundation/Columbia University Medical Center.
Drug-eluting stents have undoubtedly benefited certain patients undergoing coronary interventions. The move toward considering these stents the standard of care has called into question the utility of IVUS and FFR during percutaneous intervention (PCI).
According to Mintz, the essential lessons of a successful PCI learned during the era of bare-metal stents — to expand the stent and cover the edges to reduce the risk of restenosis — are still relevant as cardiologists rely more on drug-eluting stents.
“We should still do what we learned during the bare-metal stent era — perform appropriate vessel sizing and aim for the appropriate vessel endpoint,” Mintz said. “We should approach each and every one of our patients as individuals, with sound clinical decision making. We should only treat patients with lesions that warrant treatment, and we should optimize the quality of the results.”
Assessing lesion severity
Diagnostic IVUS and FFR can be useful for assessing lesion severity and left main coronary artery disease, as well as when angiogram and clinical symptoms do not correlate (Figure). Both have been validated in the medical literature for use in left main coronary artery disease; IVUS has shown that patients with lesions greater than 3 mm2 are at greater risk for ischemic events.
The angiogram alone has proven unreliable in assessing left main coronary artery disease, Mintz said. “We believe that invasive imaging, such as IVUS, should be used when you are unsure whether there is significant left main coronary artery disease.”
Mintz said that the best IVUS determinant of left main coronary artery disease is a ROC curve separating FFR above and below 0.75 vs. IVUS findings of a minimal lumen diameter of 2.8 mm and minimal lumen area of 5.9 mm2. These findings are relevant for two reasons: these markers correlate well with left main coronary artery disease, and left main lumen area less than 6.0 mm2 (or an MLD < 2.9 mm) is flow limiting.
However, the treatment decision — to treat or not treat — changes in patients at higher risk for left main coronary artery disease, such as in patients with diabetes. Therefore, sound clinical judgment becomes that much more important to make a proper treatment decision for individual patients, Mintz said.
He added that clinical expectations have risen since the incorporation of drug-eluting stents into clinical practice. The risks for restenosis may be higher with drug-eluting stents, while the relative cost of performing IVUS or FFR is demonstrably lower.
Given the variability in findings, the ultimate determinant of whether to use invasive imaging should be clinical judgment. “You should do what you do routinely and what you do best,” said Mintz.