Robotics In Percutaneous Coronary Interventions

Interventional cardiologist with Dr L H Hiranandani Hospital Dr Ganesh Kumar has teamed up with eminent international members to develop and test the world’s first robotic equipment for angioplasty. He writes about the advantages of this path-breaking technology.

Percutaneous coronary intervention (PCI) has become the major method of revascularisaion for coronary artery disease, with over two million coronary interventions performed annually. Recently, drug-eluting stents (DES) have shown sustained advantage compared to bare metal stents, with a marked reduction of restenosis rates. This treatment modality is becoming the major method of revascularisation.

The technique involves the use of a coronary guide-wire manipulated under fluoroscopic control across the stenosis, followed by balloon dilatation (optional), stent implantation and additional poststent dilatation (optional).

Hazards Of Using Conventional PCI

PCI is typically performed via the groin artery with the operator standing next to the patient. The catheterisation laboratory personnel operate in an unfriendly environment, subjected to a continuous X-ray radiation throughout life. This has been unchanged since the beginning of the field of interventional cardiology more than 25 years ago. In spite of education for protection and the use of lead shields and lead aprons, a significant amount of radiation is still absorbed by the operators, swith subsequent long-term radiation hazards.

Despite this concern, there is no alternative to the current methodology, where the operator is continuously exposed to radiation. There is growing concern among operators regarding the radiation dose delivered during interventional procedures, particularly in view of the increasing frequency and complexity of these techniques and the growth in the expected number of PCIs. In addition to the radiation risk, spine problems are a major burden on angiographers.

‘Interventionalist’s disc disease’ is a well-confirmed entity with cardiologists reporting more neck and back pain, more subsequent time lost from work, and a higher incidence of cervical disc herniations, as well as multiple level disc disease.

Wearing lead aprons lead to long-term problems with 83 per cent of backache problems, neck pain and shoulder pain. The additional stress on the operator can theoretically lead to degraded accuracy and performance of the operator.

Remote control robotic interventions have been suggested for surgical and radiological procedures and have been used for remote and even transatlantic operations. Increased accuracy has been a focus of such systems in surgical applications.

The Research

It was our aim to develop a remote control robotic manipulation system for PCI that allows the physician to navigate the guide-wire and angioplasty devices, in a convenient, radiation-free environment, and provide him with tools for increased procedural precision. The system developed is a wire and stent/balloon manipulation system that is operated by the physician through a computerised joy-stick and includes wire advance and rotate actuator and a stent/balloon advance/retract module. Below, I have described the system, the preclinical experiments and the first in man (FIM) study in 15 patients with single vessel coronary artery disease.

Device Description

The Remote Navigation System (RNS) is built with a bedside medical device manipulation unit located at the patients table and an operator control unit which is placed at a remote location and can be placed in a different room as required. The bedside unit manipulates the guide-wire and the angioplasty device (balloon, stent etc), and the operator control unit is placed conveniently either within the catheterisation laboratory behind lead shields or at a control room. The medical device manipulation unit includes the guide-wire (GW) base (motor and motion sensors) and a device (stent/balloon) base (motor and motion sensors).

The detachable units include the GW manipulator unit which navigates the guide-wire by advancing, retrieving and rotating and the device manipulator unit, which navigates the angioplasty device by advance/retract modes. In addition, a Y-connector holder interfaces between the guiding catheter and the wire and stent manipulators.

The operator control unit, located away from the patient bed, is the interface between the operator and the bedside unit. It is comprised of a computer, control console (including a touch screen panel to interact with the operator), and a joystick for movement control. This controls the wire motion by a continuous advance/rotate mode. In addition, a discrete angle mode of wire rotation (by 30 degrees steps) is provided. Similarly, the device can be guided by a continuous motion and discrete steps modes. Each of the units works interchangeably, and when either of the device/wire units is functional, the other one is locked in its position.

Preclinical Studies

The system was tested initially in a glass coronary model with visual feedback of the device movements through the transparent glass. The model has shown that the wire can be easily manipulated to any vascular branch by the advance/rotate modes, and that the device could be easily positioned at the desired location.

A normal coronary sheep model was employed to test the safety of the system. Following femoral artery canulation with a 7F sheath, a guiding catheter (6-7 F) was used to cannulate the coronary artery. The RNS system was positioned and the guide-wire and device loaded. The guide-wire (0.014”, variable manufacturers) was navigated within the coronary artery and placed in a distal position.

Following guide-wire navigation and positioning, the angioplasty device (balloon or stent) was navigated to its position over the guide wire. Under fluoroscopy examination, a proper location within the coronary artery was chosen for balloon inflation, stent delivery and dilatation. Following the procedure, an angiogram was performed. The procedure was repeated in each animal for several times and eventually a single stent or more were implanted.

Pilot First In Man Clinical Study

The pilot FIM clinical study was conducted in 15 patients with single coronary artery narrowing. The target coronary artery was cannulated with appropriate guiding catheter. Following baseline coronary angiography, the bed-side unit of the RNS was hooked to the guiding catheter using a Co-Pilot Y connector. Contrast injections were done using standard techniques. The system was then loaded with the coronary guide-wire (0.014”, Floppy wire) that was manipulated to its location distal to the target lesion with the RNS. Following guide-wire placement, the angioplasty device was loaded and driven to its location with the RNS.

Discrete mode was used for precise balloon or stent positioning. Lesion predilatation and post-stent dilatation following stent implantation were performed at the discretion of the operator. Coronary injections and balloon dilatations were done manually. Stents were routinely expanded at 12-14 atmospheres.

Discussion

This is the first report of PCI using a remote control navigation system. We have shown that PCI with stent implantation can be safely done with a remote control navigation system, allowing for accurate guide-wire navigation and precise angioplasty device positioning.

With the computer-controlled mechanical system, the wire can be advanced/rotated and therefore manipulated as needed, and the balloon/stent can be advanced or retracted as required, with a unique discrete motion mode allowing precise and accurate positioning. Robotic manipulation of surgical devices has been reported for several applications, including computed tomography-guided biopsy and surgery. In fact, it has been shown that such procedures can be done with appropriate communications even across the ocean. However, the intravascular application of such a system, aimed to perform coronary interventions has not been described before. While the unique feature of robotic surgery is the ability to manipulate devices in the three dimensional space, based on direct visualisation of the site, the current system uses the tree branching of the coronary system to advance the wire to its desired location based on only two degrees of freedom (advance/retract and rotate).

Guide-wire handling takes place with a combination of these degrees of freedom or either one of them. This is similar to the reality in the catheterisation laboratory, where the cardiologist navigates the wire using these same two degrees of freedom, aided by visual control by the X-ray fluoroscopy image.

In addition to that feature, the device can be advanced and retracted from the site by user-friendly options for precise positioning of the system. In simple terms, the system allows the operator to perform controlled and delicate interaction between two degrees of freedom for the guide-wire and one degree of freedom for the stent, using visual fluoroscopy control in order to remotely perform the PCI procedure.

With the ever-increasing number of PCIs worldwide, the load on the operator is increasing, with rising X-ray exposure and consequences of wearing heavy protection lead aprons for long hours on a daily basis. The potential harmful effects of exposure to radiation are well-known. The maximum recommended exposure by the National Council on Radiation Protection and Measurement (NCRPM) is five rems/year for the total body.

Interventional cardiologists receive 0.004 to 0.016 rem/case. With 500 cases a year, an average interventional cardiologist is exposed to 500x0.01= 5 rems/year. Over a professional life-time of 20 years, the operator may reach a cumulative dose of 100 rems and more.

Beyond radiation effects such as the development of cataracts and thyroid disease, the additional risk of fatal cancer from radiation exposure in the cardiac catheterisation laboratory is difficult to estimate. However, some data from the literature that propose 0.04 per cent increase in cancer per rem , times total cumulative rem exposure, lead to a rough estimate of up to four per cent increase in the risk of cancer. The exposure of ionising radiation to the operators in the field of interventional cardiology is constantly increasing, with increased fluoroscopy time, increased number of complex procedures and the increasing role of PCI in the forthcoming years.

In addition, the effect of back problems on the ability of the operators to perform procedures is already becoming a major factor, with operators refraining from catheterisation procedures either temporarily or permanently due to low back problems. The angiographer spine disease has become a well-known entity. Therefore, due to the factors mentioned above, and with this large number of procedures and its continuing growth, a majority of them having the similar pattern, there is a room to examine the role of remote control navigational methods in the catheterisation laboratory. Such systems that allow remote performance of the procedure according to the operator instructions can increase procedural safety and precision and may eventually include some of the elemental functions of the procedure in a semiautomatic, robotic fashion.

The potential advantages of a remote catheterisation system are:

1. Minimising operator hazards due to radiation exposure and spine problems.
2. Providing a convenient working environment that will increase the ability of the operator to deal with long procedural hours.
3. Enhancing the precision of balloon and stent positioning, which may be an extremely important feature in DES therapy.
4. Including semi-automatic procedures robotically controlled by the system, obtaining continuous image base feedback data.
5. Increasing the efficiency of the operator, by removing the need for an assistant and by making the process more efficient and reproducible. Operator-based errors can be avoided by a computerised system.
6. It is a matter of connectivity. Today we showed that the operator can sit out of the catheterisation room and do the procedure. This can translate in performing procedures from longer distances, probably transatlantic in the future.

This is the first report of a clinical study of a remote control PCI and it is clear that the limitations below will need to be addressed in the future. In this pilot study, the system was applied to relatively simple lesions, avoiding difficult cases, such as total occlusions, calcified lesions and excessive tortuousity. The system is currently limited to visual (image based) feedback and does not provide mechanical force feedback of the instruments. While it is clear that the visual feedback plays a pivotal role in PCI, it is not clear if the forces felt by the operator are important for a safe and successful procedure. In our system, safety limits on the forces are simply introduced by the slippage of the wire or balloon within the driver mechanism. If the guide-wire or balloon meets excessive resistance, a slippage prevents further advancement of the device and the motion is halted.

The current prototype has focused on guide wire and device manipulations by the robotic guidance system. It is clear that future models should include an integrated automated contrast injection ability, as well as remote balloon inflation unit. The on-line communication with the patient is obviously of value in generating trust and confidence of the lightly sedated patient and the medical team. A powerful communication with the patient through a video camera is one alternative. With the remote catheterisation system, we do not expect long time of absence of staff from the room, since a circulating nurse and technician will continue to enter the lab as needed.

The accuracy of stent placement is sometimes hampered by motion of the stent relative to the coronary artery generated by cardiac contraction. While the current prototype is not designed to solve this limitations, future image base control can correct for these in-accuracies by either synchronising the motion of the device to the motion of the heart, or by synchronising a quick inflation within a quasistatic phase of the cardiac cycle. This is a feature that cannot be done manually, but can be done with a computer controlled system.

Conclusion

We have shown for the first time in patients that remote control PCI is feasible and can be safely performed in patients by the RNS. We have shown that stent deployment can be adequately performed in patients with coronary artery stenosis using this system. The RNS offers radiation safety and provides convenient conditions for the operator, and can increase the precision of stent therapy in the catheterisation laboratory. This report opens the door for ergonomic technological developments in the catheterisation laboratory, aiding the physician in achieving his therapeutic goals.