Medical Device Daily Associate

ATLANTA – New imaging technologies are poised to impact the way cardiovascular surgeons and clinicians do their work, according to a special panel discussion during last week's American College of Cardiology (ACC; Bethesda, Maryland) annual scientific sessions here.

These technologies include the latest non-invasive imaging modalities via cardiac CT and MRI, new intravascular imaging technologies to identify plaque morphology and configuration and new tools to identify vulnerable plaque.

Presenting what he called a “landscape view“ of the future of cardiology imaging was Peter Fitzgerald, MD, PhD, associate research professor of cardiovascular medicine at Stanford University (Palo Alto, California). Fitzgerald said that in the cath lab, physicians are beginning to broaden their focus from just coronary stenosis with an array of technical tools for treating heart failure, vulnerable plaque, atrial fibrillation, patent foramen ovales and new percutaneous valve technologies, to name but a few.

For these, Fitzgerald said, “The one issue that all those new tools have is guidance. Guidance is going to be key to be able to provide not only applications but also extremely safe technologies to our patients.“

He described innovations in optical technology that allow the physician to see through blood, with such systems evolving from initial use in the military. These new systems are important, Fitzgerald said, because miniaturized versions now can be placed on the tip of a catheter to develop true guidance for angiography, coronary sinus navigation and circumferential ablation.

As an example, he described the SPY system, which helps to confirm that a cardiac bypass surgery operation has been as successful as possible, thereby avoiding repeat surgery and reducing complications. Developed by Novadaq Technologies (Toronto), the SPY intra-operative imaging system is an FDA-cleared fluorescent strategy useful for coronary artery bypass graft surgery, the most common open-heart surgery in the country, with about 400,000 such procedures every year.

“This is essentially night vision,“ Fitzgerald said of the technology.

FDA-cleared in January 2005, SPY uses an infrared laser to stimulate a fluorescent imaging agent injected into the blood stream. When stimulated, the agent lights up the blood in the veins and arteries in real time, and the camera – which produces an ultra-high speed image at 30 frames per second – shows live images of the heart. Captured via computer, these images can be saved and printed for reference.

Describing next-generation developments in intravascular ultrasound (IVUS) was Gary Mintz, MD, of the intravascular ultrasound imaging and cardiac catheterization laboratories at Washington Hospital Center (Washington), first asking: “What does the next generation of IVUS technology have to do?“

His answer: “I think we have to work on things like transducer frequencies. There's an issue of mutual resolution with current IVUS frequencies. It is possible to design dual frequency testers that incorporate very high frequencies that allow us to look at fibrous caps.“

Mintz also noted the need for catheters “that perform like a balloon.“ And he emphasized the need for wireless connections in the cath lab, noting that “the rest of the world has become wireless.“ Also important is consistent image quality, “so that you can expect to see the same kind of images from one case to the next.“

An example of the newest IVUS, he said, is the Smart TGC (Time Gate Compensation curve) developed by Boston Scientific (Natick, Massachusetts), a device designed to adapt to individual catheters. Another company development is Dynamic Review that accounts for blood speckle.

And Mintz cited a device from Volcano (Rancho Cordova, California), called the Virtual Histology IVUS system, which enhances intimal border recognition. A clever thing that company did with this system was to “morph the images so that they could do accurate comparison of histology and the IVUS to teach the computer how to recognize plaque characterization.“

Though virtual histology is in early testing, and does not detect all the materials in the coronary artery, Mintz called it “a step beyond grey-scale in looking at plaque composition.“

Another imaging modality he noted, being developed in Japan, is called Integrated Backscatter IVUS, a system for classifying and color-coding plaque as either calcified, fibrotic or lipid pool.

As for catheters, Mintz said that the Medical Positioning System from MediGuide (Haifa, Israel) incorporates a global positioning system that enables real-time 3-D intra-body navigation combined with any medical imaging modality.

For the cath lab of the future, Mintz said that a critical component must be system integration. “This nonsense of having to wheel in the cart, find all the components and put it together is really counterproductive,“ he said.

Such a system, in his estimation, should be easy to use and inexpensive and that a company should be able to sell two and one-half to three integrated units as opposed to one stand-alone unit.

Albert Reizner, MD, of the DeBakey Heart Center (Houston), described the use of magnetic-assisted intervention in the cath lab, characterizing such systems not as “imaging“ technologies but rather as “guidance“ technologies, and that in the future such systems would incorporate both elements.

As an example, he cited the Niobe magnetic navigation system from Stereotaxis (St. Louis), which uses two magnets that orient in a variety of directions to create a magnetic field. The magnetic field then directs and digitally controls the magnetic distal tip of an interventional device such as a catheter. The system is integrated with Siemens Medical Solutions ' (Malvern, Pennsylvania) Axiom Artis flat-panel detector system, allowing physicians to generate remote control of magnetically steered catheters from the control room.

“By changing the direction of the vector, the magnet follows that pathway,“ said Reizner. “The [guide] wire is merely a passive attachment beyond it. Importantly, despite multiple turns, you don't lose the torque in the wire.“

He noted that a key opportunity in magnetic-assisted intervention is the computer merging of imaging, navigation and therapeutics, to create 3-D images. Using this approach, Paieon (Rosh Haaiyn, Israel) is developing 3-D reconstruction by overlaying two 2-D images. This creates an endoluminal view that aids in navigation.

The ultimate “holy grail“ for this type of imaging, he said, would incorporate a technology that provides “true“ 3-D imaging using a CT-based navigational system. “This could be particularly useful in the treatment of chronic total occlusions,“ he said, providing guidance, in tandem with X-ray images to map out the best treatment pathway for a patient.

Ultimately, Reizner said he envisions a cath lab of the future in which the cardiologist will no longer be needed at the bedside. Rather, he believes these new imaging and navigation modalities will enable the cardiologist to perform a procedure from a remote location.

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