News | April 15, 2007

Physicians Speak Out on Role of IVUS in Wake of ACC Trial Data

April 16, 2007 - Volcano Corp. asserts this week that data from the COURAGE and SPIRIT trials presented last month at ACC suggest the need for more detailed imaging and diagnosis to optimize stent placement with technologies such as intravascular ultrasound (IVUS) and fractional flow reserve (FFR).

"Noninvasive imaging modalities, like CT angiography (CTA) and other screening tests, are very effective at guiding patients with coronary artery disease into the cath lab, and allowing interventional cardiologists to treat the patients that would clearly benefit from interventional therapy, said John McB. Hodgson, M.D., FSCAI, a past president of the Society for Cardiovascular Angiography and Interventions, and chief of Academic Cardiology at St. Joseph's Hospital and Medical Center in Phoenix, AZ.

"However, these first-pass screening tests also bring patients into the lab with less severe disease," he continued."These patients may also benefit from medical therapy alone and effective follow-up. In many cases, physicians are presented with the dilemma of balancing a positive CTA with a negative angiogram, then having to choose between intervention and medical therapy. Technologies like IVUS and FFR provide important objective measures of disease severity - essentially serving as the 'tie breaker' in these patients as the data supporting lesion significance related to IVUS and FFR measurements has been well studied."

The COURAGE data showed that angioplasty and stenting did not reduce the risk of heart attack or death in the 2,300 patients who participated in the study with stable coronary disease versus medical therapy and lifestyle changes alone. Although the design of the study has been vigorously debated, the COURAGE data highlights a lack of clarity as to which patients benefit from stenting, and that angiography alone may not adequately or reliably triage these target patients.

"Most heart attacks do not occur because of a blood clot at the site with the worst narrowing in the coronary, said Steven Nissen, M.D., president of the American College of Cardiology, in a national broadcast interview. "Most heart attacks occur at a site with relatively minor blockage in the coronary, and so the very sites where you put a stent are not the ones likely to cause the next heart attack or sudden death. Putting a stent in the most narrowed area in the artery doesn't really address the underlying problem"

Scott Huennekens, president and CEO of Volcano Corp. commented: "Angiography alone is severely limited in this regard as it can only diagnose vessel narrowing in 2D, and delivers no detail as to atherosclerotic plaque present or state of the disease at the narrowed, or the visually 'clear' parts of the artery. IVUS on the other hand provides a 3D 'slice' of the diseased artery so physicians can quickly and accurately measure minimum lumen diameter, remodeled vessel size, and cross sectional flow area. Volcano's proprietary VH IVUS technology also provides a snapshot of the tissue type along the length of the artery, again providing more detail to supplement angiography. This technique - used as part of the PROSPECT trial - may deliver important insights into what a vulnerable lesion looks like before a heart attack."

Dr. Hodgson continued, "We learned from the DEFER study that FFR can be an effective way to assess lesion severity. By measuring the pressure gradient across a questionable blockage, FFR provides a key objective benchmark from which to guide appropriate therapy. If the FFR is below 0.75, data suggest that the lesion will likely be associated with ischemia. In these cases, PCI should alleviate symptoms. If the FFR is above 0.75 data suggest the patient may benefit from medical therapy, follow-up and no stenting. FFR provides the physician an effective diagnostic tool to determine the appropriate treatment of the lesion and patient."

An additional important observation of the COURAGE data, according to Volcano, was that 34 percent of patients in the stent group continued to experience angina 12 months after stent implantation.

"This observation underlines the fact that in many cases we are either treating the wrong location because we didn't use FFR to measure lesion severity, or we are placing the stent sub-optimally because we are not using IVUS to ensure full apposition and expansion post intervention," said Huennekens. "The data is starting to add up."

Gregg W. Stone, M.D., of Columbia University Medical Center and the Cardiovascular Research Foundation, presented IVUS data from the Abbott SPIRIT III US Pivotal study where the Xience drug eluting stent was randomized against Taxus. The data from the core lab showed that despite the importance of optimal stent placement as part of this key pivotal trial, of the 133 stents guided by angiography alone, stent mal-apposition was observed by IVUS in 34.4 percent in the Xience group and 25.6 percent in the Taxus group.

Marco A. Costa, MD, PhD, FACC, FSCAI at the University of Florida, Shands Hospital in Jacksonville FL, commented, "The prevalence of sub optimal drug-eluting stent deployment in patients guided by angiography in today's clinical practice is staggering. The STLLR study sponsored by Johnson & Johnson using angiography guided DES treatment in 1,419 patients showed that current DES deployment techniques lead to some form of geographic miss in 66.5% of patients. What is more alarming is that geographic miss has in turn negatively impacted patient outcomes, with significantly higher TLR, TVR, and myocardial infarction rates in patients where the stent was not placed properly. A re-examination of stent placement technique including the use of IVUS is certainly warranted."

IVUS was used in live case broadcasts throughout the ACC to optimize stent placement.

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