Reducing Lead Apron Wear Time and Radiation Exposure with Remote-Controlled PCI: The Corindus CorPath

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PCI Evolves, Bringing New Problems for Operators

PCI has evolved significantly during the last quarter century. According to a market report prepared by Morgan Stanley, the number of global PCI procedures is expected to exceed 2.6 million cases by 2008.2 With advances in diagnostic tools, pharmacologics, and revascularization therapies, nearly four times as many patients are being referred to PCI rather than to surgery.³ Patient and/or physician preference, as well as shorter time delays between angiography and PCI (compared with time delays between angiography and CABG), may have contributed to selecting PCI over surgery. ³ Furthermore, a trend toward primary PCI over CABG as a means of treating patients with single-vessel and multi-vessel disease is on the rise. The availability of drug-eluting stents has also impacted the treatment strategy of coronary artery disease (CAD) ⁴ and contributed to increases in PCI. With the increased demand for PCI, physicians are placed at increased risk of exposure to x-ray radiation. ¹ The demand for PCI procedures has left many practitioners, over time, with orthopedic and other health-related problems. These problems are not uncommon and have been reported by Ross et al. ⁵

Leaded aprons are worn to minimize the interventionalist’s exposure to radiation. Although leaded apron technology has evolved over the years, a 2004 study by Goldstein and colleagues in Catheterization and Cardiovascular Interventions on the prevalence of occupational hazards of interventional cardiologists reported that 50% of operators suffered from orthopedic spine problems, primarily of the lower back, in addition to nearly 30% of interventionalists reporting hip, knee, and/or ankle problems. ¹ Disturbingly, many [operators] have personally experienced or are aware of colleagues who have suffered orthopedic problems, particularly those related to the spine, not uncommonly resulting in missed days of work, surgery, or, in some cases, curtailed careers. ¹ The investigators observed a correlation between annual caseload and years in practice as the main predictors of spine problems. This incidence is dramatically higher than that reported in the standard population by the CDC National Center for Health Statistics, which in the year 2000 documented an age-adjusted rate of chronic back conditions of 23 per 1,000 population (2.3%) among persons ages 25 and older. ¹

Additionally, the prevalence of orthopedic disease is the result of the dramatic evolution of the workday lifestyle of busy interventionalists. ¹ Prior to the surge in PCI demand, interventional cardiologists would work a few days in the cath lab, primarily performing diagnostic cases, or perhaps performing three or four cases per day with fluoroscopy times not exceeding 15 minutes per case. ¹ However, in the modern cath lab, interventionalists are spending more days per week (in some cases twice as many days per week than in previous years), performing five or more cases/day (fluoro time 20-30 min/case). Orthopedic complications to the cumulative effects of bearing the weight of leaded aprons and poorly designed catheterization laboratory environments promote awkward orthopedic ergonomic postures (e.g., monitors placed out of the line of natural working sight views). ¹ Although there have been significant improvements in leaded apron design in the last decade, over an operator’s lifetime, the cumulative exposure to radiation, in addition to wearing heavy leaded aprons, can lead to debilitating problems, a problem diagnosed as interventional disc disease.

A study by Ross et al hypothesized that there was a higher prevalence of spine problems in interventional cardiologists as compared to orthopedic surgeons and rheumatologists. ⁵ Ross’ group surmised that the higher rates of spine problems observed by interventional cardiologists were related to the use of leaded aprons. Cardiologists reported more neck and back pain, more subsequent time lost from work, and a higher incidence of cervical herniations. ⁵ All findings were statistically significant. Similar findings were observed by Goldstein’s group with regard to orthopedic back problems and time lost from work. ¹

However, back and joint problems are not the only occupational hazards interventionalists should be concerned about. Several studies have examined the effects of radiation exposure. Invasive cardiologists generally consider radiation to be the chief occupational hazard. ¹ Goldstein queried physicians regarding radiation-associated problems, ¹ such as cataracts and cancers. Other studies have indicated that physicians, particularly those who practice interventional cardiology, receive noticeable radiation doses. ^6,7 An editorial on how to reduce radiation exposure, published in the British Medical Journal in 2003, suggests that cath lab personnel should limit their exposure to radiation to 100 micro Sieverts in a consecutive five-year period. ¹⁷ Furthermore, cath lab personnel should not be exposing themselves to more than 50 micro Sieverts per year.

Radiation safety within the cath lab remains a concern even with the availability of improved leaded aprons and strict adherence to radiation safety protocols. Changing the protective measures and modifying the parameters of the x-ray tube can lead to significant changes in radiation exposure and the resulting risk. ⁷

A paper published by Clark, entitled How Much is Too Much? and cited in the Goldstein study regarding the concerns over radiation exposure to the modern interventionalist, calls attention to the ravages of x-ray exposure, particularly the effects x-ray exposure might have on younger interventionalists with long careers ahead of them. ¹

Early Experiences with CorPath

Reports of robotically-driven interventions, such as robotic valve surgery and robotic tool holders, date back to the late 1980’s. ^8-14 Robots have been used in surgery to help solve problems of holding and controlling instruments. ⁸ Solomon and colleagues used a robotic arm to perform robotically-guided CT fluoroscopy biopsies. The robotic arm held and advanced the biopsy needle. Since the physician’s hands did not need to be in the scanning plane at all, physician radiation exposure was dramatically reduced. ⁸ This experience was partly the inspiration behind the CorPath system.

CorPath was developed by Corindus, Inc. The system’s first experience was reported in EuroIntervention in November 2005. The aim of the study was to demonstrate that the technology, known as a remote navigation system (RNS), could be safely used to perform computer-controlled, remote PCI. ¹⁵ The investigators of the pre-clinical RNS study demonstrated that remote control, stent-assisted PCI was feasible. Corindus then sponsored a first-in-man (FIM) study, which took place at three sites: Haifa and Jerusalem in Israel and in Bucharest, Romania. The study’s Principal Investigator was Professor Rafael Beyar, MD, DSc, head of the Division of Invasive Cardiology, Rambam Medical Center in Haifa, Israel.

The results of the CorPath system’s FIM study were published in 2006 in the Journal of the American College of Cardiology. The study objective was to test the feasibility of performing remote controlled PCI in humans using off-the-shelf guide wires, catheters, and coronary stents. ²⁰ The FIM RNS study included 18 patients. The study endpoints included successfully navigating across single lesions and precisely positioning and deploying a stent. Procedures were successful if the operator did not have to revert to manual PCI. RNS PCI was compared to 20 manual PCI cases. Successfully crossing the lesions occurred in 17 out of 18 RNS cases. A stent was placed in 15 out of 17 RNS cases. Two RNS PCI cases were completed manually, due to a system malfunction. No statistical difference in total fluoroscopy times (TFT) was observed between the manual PCI group (9.1 min +/- 3.5) and the RNS PCI (8.8 min +/- 4.8). The FIM RNS study demonstrated the capabilities and relative safety of remote-controlled PCI, while allowing the operators to perform PCI procedures in a virtually x-ray-free environment.

Why Remote-Controlled PCI?

According to Tal Wenderow, CEO and co-founder of Corindus, the CorPath remote control catheterization system allows interventional procedures to be performed in a conventional manner from a remote location within the cath lab. The system not only reduces the amount of x-ray radiation to which an operator is exposed, but may also help reduce/ eliminate neck, back, and joint ailments associated with wearing leaded garments. Wenderow points out that for nearly 30 years, PCIs have been performed using radiographic guidance. Because this is the only way to perform PCI, operators are exposed to high levels of radiation over time. Adopting CorPath in the cath lab could reduce x-ray exposure significantly.

System components. The CorPath system consists of two units: a bedside unit, mounted directly to the cath lab table near the femoral access site, and the physician’s workstation. The system can use any conventional, off-the-shelf angioplasty devices and is compatible with standard 0.0014 guide wires. The workstation allows the operator to manipulate wires and other angioplasty devices from practically anywhere in the lab. Coronary injections, cath lab table and C-arm directives are features that Corindus intends to incorporate into workstation iterations. The workstation is tethered to the bedside unit through a standard communication line. The CorPath can be used once femoral access is achieved. The sequence of events is very much like a manual PCI where the operator begins by loading and exchanging wires, catheters, and stent systems into the Bedside Unit. Contrast injections, C-arm directives, table movements, and balloon inflations remain at the operator’s control. Most these actions can take place in a radiation-free environment, states Prof. Beyar.

The bedside unit electro-mechanically maneuvers angioplasty devices through patients’ arteries, explains Wenderow. He notes that the bedside unit can perform a combination of axial and rotational device movements using both the system’s continuous and discreet modes.

The CorPath system’s dual mode capability allows to operator to select the degree of precision needed to complete a procedure. In continuous mode, the interventionalist operates the system by continually using the system’s joystick. In discreet mode, the operator uses the discreet wire and stent icons located on the physician’s workstation touch-screen panel. In discreet mode, the operator can advance a wire or a stent in 0.5 mm increments.

With the CorPath system, an interventional procedure is performed in the traditional manner, moving devices from the femoral access site toward the heart and then into the coronaries, states Prof. Beyar. The system was developed with manual PCI in mind. Therefore, performing a CorPath procedure is very similar to performing a manual PCI procedure. More importantly, at any time during a remote control procedure, the operator can easily revert to manual PCI. Since we are using ‘off-the-shelf’ devices, it makes changing out devices easy.

Remote Controlled PCI: Advantages

The CorPath provides many advantages over manual PCI. First, since procedures can be performed from a remote location within the cath lab, CorPath PCI cases can reduce occupational hazards associated with daily cath lab activities. Second, transitioning from manual PCI to CorPath requires minimal training. Transitioning to CorPath PCI from manual PCI is relatively easy, as the CorPath does not change the way the PCIs are performed nor the devices the physicians use. Prof. Beyar says The decision-making process and the way the physician performs the procedure remains the same.

Other features built into the CorPath system include real-time device positioning, computer-assisted maneuvering for enhanced accuracy, workstation touch-screen features, such as large touch on-screen icons for stent and wire manipulation, precise positioning and discrete wire rotation, and a safety stop feature. Wenderow stresses that the most important benefits making the system unique are the potential to reduce procedure times, reduce cath lab staff’s exposure to harmful x-ray radiation, system compatibility with conventional angioplasty devices, and the potential to eliminate operator fatigue and injury associated with wearing leaded garments.

Jim Wade, Administrative Director of The Indiana Heart Hospital, Indianapolis, IN, sees potential value in having a CorPath system in his cath labs, commenting, I would invest in a technology that reduces radiation exposure to our physicians and staff as long as it is cost-effective and doesn’t overly interfere with productivity. Physicians and staff are increasingly concerned about the effects of years of radiation exposure and the physical burden of wearing heavy lead garments.

What’s Next?

Corindus is about to file a U.S. IDE for the CORRECT (Coronary Remote Control Catheterization Trial) clinical trial. CORRECT will take place at five centers in the Boston-Washington, D.C. corridor and the company anticipates beginning the trial by the end of 2006. CORRECT’s Principal Investigator is Dr. Ron Waksman, of the Cardiovascular Research Institute at Washington Hospital Center, Washington, D.C. The company has begun training CORRECT investigators on the CorPath system. This training is taking place at the Corindus office outside Boston, MA. Barring any setbacks, Corindus anticipates receiving FDA clearance for marketing the CorPath in the U.S. sometime in the second half of 2007.

Corindus is also exploring ways to expand the technology into other applications, such as electrophysiology and neurovascular interventions. The company’s EPPath system will be based on the CorPath core technology, while its primary function will be electrophysiology. The neurovascular application has yet to be officially titled. A neurovascular remote controlled system makes sense due to the longer duration of neurovascular procedures and the need for precise manipulation of equipment, notes Wenderow.

Corindus will unveil the CorPath system at the Transcatheter Cardiovascular Therapeutics meeting (TCT) 2006 in Washington, D.C. (October 23-25). The company has teamed up with Simbionix, a global leader in medical simulation technology, to provide hands-on, 15-minute simulated PCI case demonstrations using CorPath. For more information on the CorPath Simulation Experience, visit www.corindus.com [10].