From hybrid suites that include teams of multidisciplinary specialists working in a single room to tools and imaging techniques that improve outcomes, cath labs are increasingly equipped to handle the most complex patient populations.
The introduction of bare-metal stents as a means to open stenotic arteries ushered in a new era of treatment for patients with coronary artery disease. Drug-eluting stents (DES) improved upon their bare-metal predecessors and have since dominated the market. Effective as they are, DES are still related to potential complications, including stent thrombosis and restenosis. Interventional cardiologists are increasingly using adjunctive imaging techniques, such as intravascular ultrasound (IVUS), optical coherence tomography (OCT) and near-infrared spectroscopy (NIRS), as well as the physiologic technique fractional flow reserve (FFR), to better plan PCI and implant stents, as well as to better define high- versus low-risk lesions.
When the popular TV news show host Tim Russert died in 2008 from an acute MI caused by thrombus, many people called for a better way to diagnose and manage high-risk patients. Russert had recently passed a stress echo test and was being aggressively medically treated. Many recognized the large gap between passing a stress echo and the uncertainty of vulnerable lesions. Mark A. Turco, MD, director of the Center for Cardiac & Vascular Research at Washington Adventist Hospital in Takoma Park, Md., is working to better understand the natural history of coronary lesions, as well as the clinical implications of vulnerable lesions.
He and others are collecting lesion characteristic data for the COLOR registry using NIRS technology (LipiScan, InfraRedX). The catheter-based technology emits infrared light waves to acquire a “chemogram,” which is color-coded to show the various components of plaque.
“I use the technique on patients who may have diffused disease and the stenoses are in the intermediate range, 40 to 50 percent,” Turco says. “If we see plaques with a high fat content, we want to either continue treating the patients with aggressive therapy or if we move to intervene, the spectral scan gives us a feel for the length of the lipid core, which informs the amount of stenting we will need to treat that area.”
While LipiScan is FDA-approved, reimbursement is rare. Turco and others hope registry data will provide evidence that the use of the technology saves downstream costs by improving stenting results, thus reducing or preventing the need for repeat revascularization, as well as reducing the rates of acute MI caused by stent thrombosis. In addition, interventionalists can employ the use of embolic filters when stenting lesions with known large lipid cores, Turco says.
Plaques with thin caps are at a high risk of rupture. However, a thin cap in and of itself is not sufficient to indicate the vulnerability to rupture, says David G. Rizik, MD, medical director of invasive cardiology at Scottsdale Healthcare in Scottsdale, Ariz., and a co-investigator of the COLOR registry. “At the epicenter of most thin cap fibroatheromas is a lipid core and we’re hoping that the interrogation of the lesion with NIRS technology will indicate the correlation between the amount of lipid core and the predisposition to rupture,” Rizik says.
At ACC10, Rizik and colleagues from the COLOR registry, presented a study showing that higher lipid core plaque burden is associated with a higher-risk of post-PCI acute MI (AMI) and that NIRS allows identification of these high-risk patients. While the average treated segment length was comparable between those who experienced post-PCI AMI and those who had stable cardiac biomarkers, the post-PCI AMI group had a significantly higher lipid core burden.
Rizik is cautious about issuing any dogmatic statements about the technique, saying it’s still too early in the investigation. One question to answer is whether stenting those lesions will help prevent them from rupturing and developing thrombus within the vessel itself.
In a report of four case studies, Rizik and colleagues reported that one male patient with unstable angina experienced deterioration in TIMI flow after deployment of balloon angioplasty (J Am Coll Cardiol Img 2009;2;1420-1424). TIMI flow was restored and a repeat NIRS scan revealed that the pre-intervention lipid core had