Highlights from SCAI 2014 | CardioSource WorldNews Interventions
A new method for identifying hidden lesions substudy, the benefits of personal radiation monitoring, and more from the Society for Cardiac Angiography and Interventions (SCAI) 2014 Scientific Sessions.
3D (and 4D!) Angiography Helps Identify Severe Coronary Lesions
Three-dimensional quantitative coronary angiography (3D-QCA) accurately identifies hard-to-see coronary artery lesions that merit further evaluation. It's an important issue given that in patients with symptoms or tests suggestive of coronary artery diseasebut visibly underwhelming disease on angiographydiscrepancies in how the angiogram is interpreted can lead to a wide variation in treatment and concerns of over- or under-treatment.
The IQ-CATEGORIZE Lesions Study evaluated the reliability of 3D-QCA as a simple tool to determine lesion severity. (Or 4D-QCA if you include the length, height on angiography, depth, and the fourth dimension of timeor, more specifically, change in shape over the time of a cardiac cycle.) It has become fairly routine to use the caliber of the coronary catheter to determine stent size.
In 3D-QCA, a 3D image is created in a similar way, by using the catheter's size in two or more angled views to create a proportionate 3D image. To evaluate 3D-QCA's accuracy, researchers reviewed 131 suspicious lesions in 79 symptomatic patients, most with functional evidence of significant disease but only 30-70% stenosis by singleview QCA.
They compared average minimum luminal diameter (MLD) from two angulated views to the inlesion percent plaque area stenosis (%PAS), a highly accurate measure taken by coronary intravascular ultrasound (IVUS). Prior studies using IVUS have established %PAS >67% in left main arteries and >70% in non-left main arteries as accurate measures of blockage severity.
However, clinicians commonly use %PAS less than other severity measures because it requires additional equipment to be passed down an artery. 3D-QCA offers potential advantages, because its 3D images are constructed using standard coronary angiogram images without the need for additional imaging or equipment. In this study, researchers used a 6 French (Fr) or 2 mm catheter severity cutoff for small (2.6-3.0 mm) and medium-sized (3.1-4.5 mm) vessels, and an 8 Fr or 2.67 mm cutoff for left main or large (>4.5 mm) vessels.
They found average MLD's less than the cutoffs measured by 3D-QCA were highly predictive of %PAS results. In small and medium vessels, 3D-QCA was highly accurate in predicting severe %PAS >70%, which is likely to indicate severe disease (93% accuracy in small vessels and 97% accuracy in medium vessels). In left main and large vessels, 3D-QCA reliably distinguished severe %PAS >67% and >70% (94% accuracy in left main and 92% accuracy in large vessels).
"In symptomatic patients, 3DQCA using the cutoffs established in this study helps determine the location of relevant severe suspicious blockages that may warrant treatment," said Charles Laham, MD, principal investigator of the study. "3D-QCA appears to be a simple yet reliable tool to help interventional cardiologists distinguish which occult lesions should be further evaluated. The technique can help improve patient care, while reducing variation in care."
For Heavily Calcified Lesions, Are Diamonds an Interventionalist's Best Friend?
Despite advances in interventional techniques, treatment of calcified coronary lesions remains a challenge. Calcified lesions respond poorly to PCI and are associated with a high frequency of restenosis, target lesion revascularization (TLR), vessel dissection during PCI, failure to deliver a stent, balloon ruptures, and undilatable lesions.
When stent placement is achieved in these lesions, the result may be stent underexpansion, malapposition, or procedural complications. With ORBIT II, we have the first study to exclusively investigate severely calcified lesions, involving high-risk patients who are usually excluded from large clinical trials, including those on dialysis or with low left ventricular ejection fraction (>25%).
"Often patients with calcified lesions are more difficult to treat because the calcium can interfere with proper stent placement," said Jeffrey Chambers, MD, director of the cardiac catheterization laboratory, Mercy Hospital, Minneapolis, and the study's principal investigator. "If the stent cannot be placed properly the patient may need additional procedures and even surgery." In the trial, investigators treated patients using the Diamondback 360° Orbital Atherectomy System (OAS). Investigators used the centrifugal action of the OAS diamond-coated crown to modify calcified lesions prior to stent placement. The device received FDA approval in October 2013.
The study, comprising 443 patients at 49 US sites, demonstrated that OAS aids stent delivery, with promising 1-year outcomes: ORBIT II met both the primary safety and efficacy endpoints by significant margins. Preparation of severely calcified plaque with the OAS not only helped facilitate stent delivery, but improved both acute and 30- day clinical outcomes compared with historic controls.
In this difficult-to-treat patient population, the primary safety endpoint was 89.6% freedom from 30-day major adverse cardiac events compared with the performance goal of 83%. The primary efficacy endpoint (residual stenosis <50% post-stent without in-hospital major adverse cardiac events) was 88.9% compared with a performance goal of 82%. Stent delivery occurred successfully in 97.7% of cases with <50% stenosis in 98.6% of subjects.
At 1 year, 94.1% percent of patients were free from target vessel revascularization (TVR) and TLR. Investigators also reported lower rates of 1-year cardiac mortality (97% freedom from cardiac death). (In-hospital and 30-day results of this pivotal trial were published in the May 2014 issue of JACC Cardiovascular Interventions.)
The data presented at SCAI 2014 also reviewed cost differences between patients who received OAS prior to stenting and those who did not. Using a sample of patients derived from 2012 Medicare data, investigators compared typical treatment costs to ORBIT II patients who were pre-treated with OAS.
Mean costs were $3,198 lower (p = 0.003) in ORBIT II patients compared to Medicare patients, with most of the difference due to faster hospital discharge in ORBIT II. After adjusting for differences in age, gender, and comorbidities, mean costs still were 17% (p < 0.001) lower in ORBIT II patients compared to Medicare patients, or approximately $2,600-$2,700. "In addition to patient clinical outcomes, pre-treatment of these difficult-to-treat, severely calcified lesions with coronary OAS resulted in cost savings due to more efficient procedures and lower readmission rates," said Dr. Chambers. "In an era where we are treating more patients while aiming to achieve better outcomes at greater value, these findings are significant. Not only does this procedure improve care, but it can do so more efficiently."
Real-Time Radiation Monitoring Reduces Exposure to Patients and Interventionalists
Radiation exposure during cardiac catheterization often leads to adverse consequences for both patients and operators. A real-time monitoring device that beeps in the presence of high doses of radiation can help reduce such exposure to patients and interventional cardiologists alike. Rather than cumulative doses measured over time, RadiCure investigators monitored physician and patient radiation exposure using a real-time, personal radiation monitoring device called the Bleeper Sv (Vertec Scientific Ltd, Berkshire, United Kingdom).
The Bleeper sounds every 15 minutes in response to normal background radiation and increases its beep rate as radiation exposure increases until it becomes continuous in high radiation fields. All procedures were performed by experienced operators trained in radiation safety and skilled in equipment use.
Researchers measured operator radiation exposure in both groups using a second silent radiation exposure monitoring device, then compared patient and operator radiation exposure between the two study groups.
For the study, 505 patients undergoing left cardiac catheterization procedures were randomized to use or no use of the monitoring device. Procedure times and patient characteristics were comparable in both study groups. Following the procedure, patient and interventional cardiologist radiation exposure was measured.
Researchers found that compared to the control group, use of the monitoring device led to a significant decrease in operator exposure: 0.9 (0.4-1.7) vs 1.4 (0.6-2.5) mrem; p < 0.001 for the first operator (a 36% relative risk reduction in overall radiation), and 0.5 (0.2-1.0) vs 0.7 (0.4-1.4) mrem; p < 0.001 for the second operator (a 29% relative reduction in overall radiation).
Patient radiation exposure did not differ significantly between the two groups; however, there was a trend for lower air kerma (AK) and dose area product (DAP) radiation in the Bleeper group, 0.855 (0.58- 1.507) vs. 0.989 (0.610-1.802) Gy; p = 0.153, and 76.68 (52.98-133.53) vs. 84.61 (55.37-161.20) Gy*cm2; p = 0.125, respectively, for a 14% relative risk reduction in total AK radiation in the Bleeper use group and a 9% relative reduction in patient DAP radiation with the device audibly activated.
The bottom line: "Use of a personal radiation monitoring device that provides auditory feedback helps reduce both the patient and the interventional cardiologist's exposure," according to Georgios Christopoulos, MD, research fellow at VA North Texas Health Care System and the University of Texas Southwestern Medical Center. A huge advantage, noted Emmanouil Brilakis, MD, PhD, director of the cardiac catheterization laboratories at VA North Texas Health Care System, associate professor of medicine at the University of Texas Southwestern Medical Center and the study's principal investigator, is that "the device allows for immediate reaction to limit exposure unlike current monitoring that occurs physicians undergo months after exposure."
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