Mapping/ablation catheters are used to treat atrial
fibrillation. Current mechanical catheters can be difficult and time consuming
to operate and hinder reproducible and consistent ablation. This article
describes new electroactive polymer (EAP) technology that provides the basis
for the development of electronically controlled steerable actuators. The EAP
technology will enable standard catheter platforms to incorporate advanced
micro-steerability, reduced procedure times and advanced automation capabilities.
The innovative electrically steered catheters will benefit millions of
Americans who are suffering from atrial fibrillation.
Strategic Polymer Sciences, Inc. (SPS) is developing electrical micro-steerable actuators
with micro-articulation capability for the integration with ablation catheters
for the treatment of Atrial fibrillation (AFib). Arrhythmias are among the most
common disorders of the heart and AFib is the common arrhythmia associated with
significant morbidity. AFib can lead to angina, heart failure and stroke. There are currently more than 2.5 million Americans suffering from AFib and
there are about 160,000 new cases diagnosed each year. The lifetime risk for
the development of AFib is an estimated 25 percent of Americans older than
forty. Treatment of AFib is essential for the patient suffering from severe and
frequent episodes of these arrhythmias. Ablation catheters are used to treat
both ventricular and supraventricular arrhythmia, and there is emerging
evidence that the ablation catheter treatment of arrhythmias is curative whereas
drug therapy and implant treatments are not curative. Although the catheter
ablation is expensive, the cost is still less over time than the cost of drug
therapy or surgical interventions. Based on recent clinical trial results, it
has been recommended that “ablation should not be reserved as a last resort
treatment but is appropriate to consider, in some cases, as first-line therapy.”
However, among the more than 2.5 million AFib patients currently in the US,
less than 1 percent are treated with an ablation procedure due to functional
limitations of current commercial cardiac catheters. Specifically, due to the
lack of reproducibility and precision in controlling the catheter tip position
by the push/pull cable in current catheters, the current ablation procedure
requires a long procedure time (2 to 9 hours), which subjects physicians and
staff to prolonged X-Ray radiation exposure, as well as to the ergonomic
challenge of standing for the duration of the procedure. Although ablation
procedures are minimally invasive, long procedure times mean an increased risk
to the patient as well.
Electro-active polymer (EAP)-based electrical
micro-steerable actuators utilize a breakthrough solid state actuator
technology, invented by one of the co-founders of Strategic Polymer Sciences,
to manipulate the catheter tip position. The linear correspondence between the
applied voltage and the dimension change in the EAP actuator enables precise
control of the catheter tip and its force level, resulting in a significantly
reduced procedure time with the added benefit of a programmable operation
capability. This allows for remote operation, thereby reducing the physician’s
exposure to radiation. The ease of integration of the proposed actuation
technology with current catheter designs will reduce risk and time to market.
Steerable catheters perform the function of mapping and
ablating, which requires precise control of:
- The catheter tip position,
- The force level at the tip, and
- The ability of the tip to reach all the required locations
in the heart.
The mapping and ablation procedures are time consuming and
challenging. The success and efficiency of current procedure are largely
determined by the skill of the operator who uses the manually controlled
catheters with limited flexibility and maneuverability.
Currently, there are active and extensive development
activities regarding improving catheter technologies. For example, using a
multi-sensor array on the tip of the catheter can shorten mapping time.
Steering the catheter tip to the desired position, however, is the first step
in an intracardiac electrophysiological study (EPS) and is critical to the
efficiency and success of the whole procedure. Strategic Polymer Sciences is
developing a steerable actuator tube made from advanced proprietary EAP-based actuators
to replace a portion of the catheter sheath and the mechanical push/pull cables
inside the current catheters. The new steerable actuator tube will be built as
a module that can be seamlessly integrated with the current mapping and
ablation electrical modules. Since the EAP-based actuators can be remotely
steered with electrical signal controlled by a computer, the steerability,
steering precision and procedure time can be significantly improved.
While the proposed EAP-based micro-steerable catheters have
marked advantages over current catheters steered manually with push/pull
cables, there are two recently developed steerable catheter technologies,
namely sophisticated robotic systems and magnetically steered systems. Although
the physician can remotely control the robotic systems, these systems cannot
reach all the heart chambers due to their bulky size. In the magnetic systems,
because a magnetic field gradient originating from magnets outside of the body
creates the force exerted on the catheter tip, the force level is low and
consequently it has low load capability. As such, ablation lesions are often
not deep enough and ablation points must be redone manually to create the
necessary lesion depth. The SPS micro-steerable actuator based catheters
largely avoid these issues.
From the EP perspective, “new ablation technologies need to
show shorter procedure times, increased efficacy, and improved safety in order
to drive widespread adoption.” SPS’s electrically, micro-steerable catheters
will combine the high strain, tunable force levels (via electric signals), and
computer controllability, which represents a revolutionary approach.
There are several ways in which the SPS design’s potential
is acknowledged to benefit EP physicians and their patients. Because of the
electrically actuated nature of this technology, the actuator system can be
operated remotely to reduce the radiation exposure of the procedure operators.
In addition, the extremely resolute level of spatial control and positioning
repeatability lends itself to quicker positioning of the catheter tip for mapping
and ablating with the potential to significantly reduce the procedure time.
Furthermore, this enhanced position control suggests that physicians with
broader range skill levels may be able to effectively operate the catheter
creating the opportunity to treat more patients over time. Finally, the
piezoelectric feature of SPS’s EAP can also be used as a force transducer to
monitor the force at the catheter tip, providing feedback to avoid damaging the
cardiac tissue. SPS EAP actuation technology in a mapping and ablation catheter
form has the potential to accommodate all of the above requirements, and makes
these procedures available to a wider group of patients giving them access to
treatments, which previously have been due largely to cost and time.