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 disappeared. Researchers concluded that the cholesterol-laden plaque had embolized, causing the no-reflow.
OCT sheds light on stent safety
OCT is another light wave-based technique to image inside the coronary arteries. In May, the FDA approved the first OCT system for cardiovascular use in the U.S. (LightLab, recently acquired by St. Jude Medical). The technique uses infrared light to create a high-resolution (10 to 20 microns) 3D image of the lesion. It does not characterize plaque composition, but researchers have found it useful to determine whether stents have been deployed fully and accurately. OCT does not image through blood, so blood must be occluded and flushed during the scan. Newer OCT technologies are quicker and allow imaging with a single saline flush. Researchers also have found success with a non-occlusive technique that infuses the vessel with a contrast agent.
“Cardiologists have long been searching for imaging tools to enhance our understanding of vascular disease and guide optimal PCI and other coronary therapeutic strategies,” says Marco A Costa, MD, PhD, director of the Interventional Cardiovascular Center at the Heart and Vascular Institute University Hospitals Case Medical Center in Cleveland. Costa also directs the cardiovascular imaging core lab responsible for analyzing results from many trials using OCT.
Costa and colleagues from the ODESSA (Optical coherence tomography for DES SAfety) trial studied the rate of uncovered and malapposed struts in overlapped versus nonoverlapped stents in 77 patients with long coronary stenoses at six-month follow-up (J Am Coll Cardiol Intv 2010;3:531-539). They used the LightLab system.
While overlapping stents are associated with an increased incidence of uncovered struts, researchers found a similar low incidence of uncovered struts in both overlapping and nonoverlapping sites, suggesting the safety of overlapping DES. However, they found increased neointimal hyperplasia at the overlap stent segments, suggesting reduced efficacy at those junctures. In addition, strut malapposition, coverage pattern and neointimal hyperplasia differed significantly among DES type—sirolimus-eluting, paclitaxel-eluting or zotarolimus-eluting stents.
Researchers did not correlate OCT findings with clinical outcomes. “Nevertheless, the low frequency of uncovered or malapposed struts in DES platforms, even in the sirolimus-eluting stents, matches the reported low rates of very late clinical stent thrombosis,” they said.
The use of OCT to assess left main coronary artery (LMCA) stenting has been limited because of the need for proximal occlusion and OCT’s limited tissue penetration. Gary S. Mintz, MD, chief medical officer of the Cardiovascular Research Foundation in New York City, and colleagues from Florence, Italy, employed a non-occlusive technique with infusion of iso-osmolar contrast agent (Visipaque, GE Healthcare) and determined at six months’ follow-up that DES in the LMCA was safe and feasible (EuroInterv 2010;6:94-99).
“OCT was able to identify LMCA stent struts that were covered, uncovered or malapposed, as well as to accurately measure neointimal hyperplasia thickness,” they reported.
OCT is subject to several limitations such as various artifacts from bubbles, vessel motion and residual blood, as well as out-of-screen phenomenon. In the case of the LMCA, its larger diameter relative to other coronary arteries resulted in out-of-screen artifacts and limited the completeness of some evaluations. Mintz and colleagues agreed that newer, faster OCT technology would overcome this limitation.
Researchers suggest that optimal evaluation of LMCA stent strut coverage may help to assess the risk of stent thrombosis and to guide clinical decision making on the duration of a tailored antiplatelet therapy for individual stent types or for individual patients.
|Top Ten Tips to Initiating a Hybrid OR|
IVUS, which uses sound waves to generate images within coronary vessels, has been extensively validated as a tool to help improve outcomes of stent implantation. “Clinically, the best data show that IVUS helps reduce complications after stent implantation—those complications being stent thrombosis, restenosis or revascularization,” says Mintz. It does this by helping to ensure full expansion of the stent and by imaging potential inflow and outflow track problems, such as large plaque burdens or residual dissections at either the proximal or distal edge. “Those are the only two things that have consistently been shown to have an impact on events within the first year,” he says.
Serruys et al used a combination of IVUS-VH (virtual histology) (Volcano) and OCT (LightLab) to determine characteristics of DES at high-risk bifurcation plaques (J Am Coll Cardiol Img 2009;2;473-482). Overall, the percentage of necrotic core decreased from proximal to distal rim, while thinner caps were more often located in the proximal rim. They also found that patients with unstable clinical presentation showed a high-risk profile of plaque types at bifurcations with a higher proportion of thin cap fibroatheromas and fibrous atheromas.
Interestingly, in a sub-analysis of ODESSA at six months, Costa and colleagues, using OCT, found variable patterns of strut coverage of DES implanted at bifurcations—independent of DES type (EuroInterv 2010;6:69-77). Researchers suggest that flow patterns at bifurcations may have some bearing on strut coverage and neointimal growth.
Hybrid suites & building bridges
Not only are innovative imaging tools expanding the way interventionalists treat coronary lesions, but the “expanded” cath lab, or hybrid suite, is gaining traction, especially given the excitement for percutaneous valve procedures and the growing emphasis on multidisciplinary teams to deliver better patient care. The design of the hybrid suite will depend on the specialties that utilize it. A room used by interventional cardiologists and interventional radiologists will look vastly different from one used by interventional cardiologists and cardiothoracic surgeons. In reality, though, it’s not so much about the equipment as it is about the culture of collegiality.
“We are very strong believers that this type of multidisciplinary approach is the way the world is going and unless you have this hybrid workplace, you will be left out of much cutting-edge cardiovascular treatment,” says Michael J. Mack, MD, medical director of cardiovascular surgery at Baylor Healthcare System and co-director of cardiovascular research at Heart Hospital Baylor Plano in Texas.
Ten years ago, David Brown, MD, director of interventional cardiology and co-director of cardiovascular research at the Heart Hospital Baylor Plano in Texas, taught Mack how to perform heart caths. But not every facility will have such willing collaborators among the varied specialties.
“This lack of collaboration and convergence is a major obstacle in many U.S. institutions that perform cardiovascular procedures,” says Brown. “There are approximately 1,140 U.S. open-heart programs and the idea that this type of collaboration exists in all of them is folly. But that has to change going forward in terms of patient quality and healthcare costs.”
Building a hybrid lab is not for the faint hearted. The cost can be upwards of $2.5 million. Drs. Mack and Brown practice at two facilities. The Heart Hospital Baylor Plano has two three-year-old hybrid suites from Siemens Healthcare and Medical City Dallas has two one-year-old rooms from Philips Healthcare. “It’s important when planning for a hybrid OR to engage the hospital CEO, highlighting patient care and marketing advantages to hybrid procedures, and use vascular volumes and revenue to build your case,” says Angela Riley, RT, executive director of the Cardiopulmonary Research Science and Technology Institute, an independent nonprofit research company in Dallas. The institute emphasizes the creation of an oversight committee, including multiple specialties such as physician users and key department directors from the cath lab, OR, interventional radiology, IT and infection control, among others.
The staff should be a blend of cath lab and OR personnel, and hospital administrative support must be gained to diffuse department conflicts surrounding charging, scheduling and productivity. At the annual meeting in May of the American Association for Thoracic Surgery, a two-day symposium on hybrid technologies drew more than 500 participants. Mack, who was in attendance, said concerns were raised about where to charge the expenses. “Most accounting systems are not set up for this type of cross-fertilization,” he says.
Riley says that someone in administration needs to make the decision whether the costs will be borne by the cath lab or the OR. “CEOs have to accept the fact that these are complicated cases and they need to eliminate stress for directors and managers in those different areas,” she adds.
In many geographic regions, the volume of coronary intervention is diminishing while noncoronary interventions are increasing. Coronary interventions or CABG won’t go away, but new ways of approaching the disease process, such as in the hybrid suite, are going to become increasingly common.
To be successful with this approach, due diligence includes getting all stakeholders onboard and to answer all relevant questions: Will it be used for children, peripheral interventions or electrophysiology procedures, as well as by interventional cardiologists, radiologists, vascular and cardiothoracic surgeons? Is there existing space? Does that space have to be remodeled? Who will staff the new room? Who will bear the charges? The trend in cardiovascular medicine is a multidisciplinary approach and the increasing utilization of intravascular imaging tools. Both approaches improve patient outcomes.