Imaging Partners with Robotics: Minimally Invasive Cardiac Surgery

Through innovative technologies - such as robotics and intravascular ultrasound - surgeons are developing and employing less invasive techniques to heal patients and make their recoveries less traumatic.

For coronary disease, the treatment mainstay for years has been bypass surgery or percutaneous coronary interventions - with the lines between the two procedures increasingly blurred as percutaneous interventions became more complex with stent placement and other related applications.

While some form of intervention is the rule rather than the exception in the great majority of cases, physicians agree that less invasion is always the most prudent route.

"One of the important concepts may be that as procedures become less invasive, we also have more patients who may not need anything at all," says Jack A. Ziffer, PhD, MD, director of cardiac imaging for the Miami (Fla.) Cardiac & Vascular Institute and chief of radiology at Baptist Hospital of Miami.

The first step in making surgery less invasive is to have a patient's work-up become less invasive by avoiding procedures such as coronary angiographies whenever possible. Unfortunately, when it comes to assessing cardiac disease, there is seldom a way around a coronary angiogram or diagnostic catheterization prior to either percutaneous intervention or minimally invasive cardiac surgery.

In the next few years, however, Ziffer believes that will change, particularly with CT-based approaches for coronary angiography. Between the ever-expanding technologies of multislice CT and electron-beam CT (EBCT), faster scans and higher-resolution images will offer physicians and surgeons more insightful views into the cardiovascular system. Whether multislice CT or EBCT will be the premier technology, Ziffer says it is too soon to say, but adds that both forms of CT will be beneficial to coronary imaging.


IMAGING BEFORE AND AFTER

Using CT and MRI, surgeons can follow the success of interventions. MRI and positron emission tomography (PET) are regarded as the best tools to assess myocardial viability and whether a patient would benefit from revascularization.

While the hybrid combination of PET and CT has been used extensively for oncology imaging, Ziffer says Miami Cardiac & Vascular Institute soon will ramp-up its two PET-CT systems for cardiac work.

"PET has phenomenal sensitivity and specificity," Ziffer adds. "What it doesn't tell you is what the vascular anatomy is. CT will let the cardiologist and surgeon know whether the patient is a surgical patient or non-invasive patient."

Ziffer emphasizes that diagnostic catheter procedures will not disappear completely, because there always will be patients for whom a surgeon needs to be completely sure about what he or she is about to encounter in the operating room and the highest possible resolution is necessary. However, he adds that it is "realistic to expect in the next three years that we will get the quality of non-invasive coronary angiography sufficient so that diagnostic angiography won't be required in many patients."


NANO NANO

Being able to see and anticipate what they are about to encounter is an obvious - albeit preferable where possible - requisite for any surgeon.

"Traditionally for surgeons, if they can't see it, they can't do it," notes Randall K. Wolf, MD, professor of surgery and biomedical engineering at the University of Cincinnati (UC) and director of UC's Center for Surgical Innovation. "Our unaided human performance is limited by a 200-micron accuracy due to our visual discrimination or motor coordination. If we use sophisticated, computer-assisted or robotic systems along with imaging, we can do a lot more. We can get down to almost the nano level."

For more than a decade, Wolf has collaborated with companies such as Intuitive Surgical Inc., Ethicon Endosurgery and ArtiCure Inc. to develop new devices. About eight years ago, he began to develop a technique to perform heart surgery using what he describes as a "remote telemanipulator." That robotic device today is known as Intuitive Surgical's da Vinci surgical system. Wolf aided in the U.S. trials to gather clinical data for the da Vinci's FDA clearance. The first da Vinci was installed at Ohio State University in 1999 under Wolf's direction.

The da Vinci takes a surgeon's hand motion, turns it into a binary code, and transmits that information through servomotors to tiny instruments in the patient's chest.

"One of the things we would like to do is take a CT or MRI scan the patient had before surgery, put the disk in the machine and see the CT scan, as we are looking through the [da Vinci's] 3D vision," Wolf says. "Then we have a navigational device. We have turned it into a GPS [global positioning system] for the body."

The UC Center currently is working on a technique that would allow a surgeon to simulate an operation beforehand, based on the pre-op imaging results.

"We would like to use [the da Vinci] to simulate the surgical environment and train surgeons the same way pilots learn on a flight simulation machine," Wolf says. "We have an extraordinary opportunity to change the paradigm, teaching surgeons how to operate. We can use images taken pre-operatively and use a virtual reality system to create the environment."


BRANCHING OUT

The Minimally Invasive and Robotic Heart Surgery Center at North Shore University Hospital in Manhasset, N.Y., launched its da Vinci system in February. Cardiothoracic surgeon Robert Kalimi, MD, is a specialist in minimally invasive and robotic cardiac surgery. Kalimi joined North Shore University Hospital in January after serving as a clinical instructor in minimally invasive robotic cardiac surgery at Columbia-Presbyterian College of Physicians & Surgeons.

In his experiences, Kalimi says that "although use of the robotic technology adds to the length of a procedure, patients' benefit from smaller incisions, less postoperative pain, and earlier return to normal activity. Kalimi adds that, "the operation is performed through tiny incisions without the need to split and spread the breastbone. In addition, using a minimally invasive approach means there is less bleeding, less morbidity and patients are able to return to work sooner. In younger women, there is a significant cosmetic result. Some incisions are hidden under the crease of the breast."

North Shore expects to perform 25 to 50 cardiac robotic cases in the first year of operation. The hospital handles approximately 1,400 procedures annually. "There is a good chance that 5 to 10 percent of those operations would eventually be performed using the robotic system," Kalimi says.

Most recently, the FDA cleared the system for mitral valve surgery, atrial septal defect repairs, and thoracic procedures. With improved technologies in the future, Kalimi sees the potential for the da Vinci to be employed in operations for atrial fibrillation and for totally endoscopic coronary bypass surgery.

UC's Wolf estimates there are approximately 55 da Vinci systems installed in the United States being used for cardiac surgery, general surgery and urologic procedures.


PATIENTS BENEFITS

Johns Hopkins Medical Institutions (JHMI) installed two da Vinci systems three years ago. Since then, JHMI has performed almost 100 robotic surgeries, the majority of which have been in general surgery, predominantly abdominal procedures. Only recently have cardiac-related applications been conducted.

David Yuh, MD, assistant professor of surgery in JHMI's division of cardiac surgery, has used the da Vinci to place pacemaker defibrillator leads in patients. Traditionally, the leads have been inserted via a thoracotomy - an incision through the chest wall - which is an extensive and painful incision. With the robotic device, incisions are much smaller and, theoretically, are less painful for patients.

"If there is less of an incision to heal, the chances for wound complication or infection is reduced," Yuh notes. "From an anecdotal and clinical standpoint, it has been observed that patients are not nearly in as much pain."

Still, Yuh says, minimally invasive surgery violates one of the primary tenets of surgery, which is exposure. He says there must be a "generational turnover" in traditional surgical philosophy for minimally invasive robotic surgery to gain popularity.

"The forefathers of modern day surgery always espoused that maximum exposure leads to better operations and better outcomes," says Yuh. "In many respects, that is true. On the other hand, if one can perform the same operation with a device that enables the same benefits of wider exposure - that is, excess visualization - one can do a safe operation with a small incision."


NEW TECHNOLOGY

The 400-bed Texas Regional Heart Center (TRHC) in Plano, Texas, recently added the CrossPoint TransAccess catheter from Medtronic Inc. to its technology portfolio. The facility performs approximately 200 complex vascular procedures and approximately 1,000 coronary procedures per year.

The CrossPoint incorporates Jomed Inc.'s intravascular (IVUS) imaging technology to view images that help surgeons guide the catheter inside a patient's artery. The catheter received FDA 510(k) clearance in 2002 and is indicated for the positioning and placement of catheters within the peripheral vasculature. The device became part of Medtronic's product portfolio through its acquisition of TransVascular Inc. in September 2003.

David Prewitt, MD, TRHC's director of peripheral vascular medicine, is one of three physicians in the state now qualified to use the CrossPoint. He performed his first procedure with the device in late January.

The catheter tip is designed to, among current and potential applications, aid cardiologists to perform intravascular procedures, such as the delivery of therapeutic agents, such as cells, genes and drugs, to locations in a patient's vascular system.

The catheter with its IVUS tip can cross a total occlusion (100 percent total blockage) in an artery and reconnect at an area further downstream or distally where the lumen (the space in the interior of an artery) becomes visible again.

"Technically, we can cross most of these with a wire, but there are frequent instances when we can't get back into that lumen, where you are basically under a piece of tissue that will not allow you to gain access back into that artery," says Prewitt. "This catheter allows you to see where the true lumen is and position the catheter. It incorporates a needle, which pierces the covering of artery back into the lumen. Once you can do that, you gain access back into the lumen."

Other potential applications include the repair of heart tissue that results from heart attacks. The CrossPoint TransAccess would be used to deliver cells to regenerate and restore the tissue to damaged portions of the heart.

Before the advent of the CrossPoint, if physicians entered the small channel where they could no longer gain access distally, they were unable to complete the procedure.

"It would have meant open bypass surgery," Prewitt says. "Sometimes we would bring a patient back two or three times before we got lucky for a second or third attempt before we were successful."

Prewitt spends one day a week educating other physicians on the CrossPoint technology, which also is expected to reduce procedure times. The center is expected to become one of the training centers for this technology in the central United States.

The learning curve to learn how to use the technology will depend, in part, on a physician's previous experience, but Prewitt does not anticipate a lengthy ramp-up.

"It will cut down the learning curve, because you don't have to be as good to try to get in the lumen," he says. "If you don't get in the lumen, you have this catheter. Beforehand, if you were unable to get in the lumen, you had to have a lot of experience getting in the right places. Now you don't have to have that experience; you can get in the wrong place and this [catheter] will get you to the right place. It will help people with less experience get out of trouble."


MAPPING PROCEDURES

Massachusetts General Hospital (MGH) early this year began to offer digitally controlled catheter-based procedures with the installation of an Axiom Artis dFC magnetic navigation system from Siemens Medical Solutions USA Inc.

Siemens developed the system by combining its Axiom Artis dFC flat-panel detector system with Stereotaxis Inc.'s Niobe magnetic navigation system to direct and control catheter- and guidewire-based devices within the heart and coronary vasculature.

"The purpose of this combined imaging system with permanent magnets is to allow clinicians - electrophysiologists and interventional cardiologists - to navigate through the body's vasculature to very specific anatomical points to do interventions, such as electrophysiology ablations or placements of stents in coronary vasculature," says Kelly Feist, Siemens' segment manager for the Axiom.

The Axiom has been available commercially since the first half of 2002. Siemens expects to have 15 to 20 installations in the United States by the end of this year.

The system uses computer-controlled permanent magnets for orienting the magnetic tip of specially designed catheters and guidewires. The approach is designed for 360-degree rotation of the catheter.

Jeremy Ruskin, MD, director of MGH's cardiac arrhythmia service, says the technology is an important first step toward the use of computerized controls in cardiac electrophysiology.

Feist adds that the technology potentially could "do some of the mapping procedures that are required in electrophysiology to determine where the arrhythmia originates from. If doctors can pinpoint that through mapping, then they can intervene using ablation techniques."