Feasibility, safety and efficacy of Subcutaneous Electrical Nerve Stimulation (SENS) in patients with chronic refractory angina pectoris. A pilot study.

Angina pectoris is the main clinical symptom accompanying ischemic heart
diseases.
The majority of patients suffering from ischemic heart disease can nowadays
adequately be treated by either anti-ischemic medication or by
revascularization procedures such as Percutaneous Coronary Interventions (PCI)
or Coronary Artery Bypass Grafting (CABG).
Despite the development of these pharmacotherapeutic and surgical treatment
strategies, there is a group of patients that remains severely disabled by
their anginal complaints.
Since 1982 numerous studies have demonstrated that neurostimulation by means of
Transcutaneous Electrical Nerve Stimulation (TENS) or Spinal Cord Stimulation
(SCS) is an effective additional tool for these chronic disabled patients.
However, because of some complications (ortho-ergic skin reactions in TENS and
epidural lead migration in SCS) related to these well accepted forms of
neurostimulation (accepted into ACC/AHA guidelines, class 2 indication) it
seems worthwhile to search for new alternatives.
Subcutaneous placement of the electrodes by using Subcutaneous Electrical Nerve
Stimulation (SENS) may be a good option. SENS involves positioning electrodes
just underneath the skin and can be used to target nerves and nerve endings in
very specific regions, including the localized parasternal regions on the chest
where patients usually experience their anginal pain.
The subcutaneous electrode placement, in contrast to the epidural placement in
SCS, creates an easier accessible and less risky route. Moreover, the area for
subcutaneous electrode placement in SENS is larger and small shifts of the
electrode leads will not have immediate consequences for the therapy.
Furthermore, there is no need for fluoroscopy to verify the position of the
electrodes and SENS seems also more suitable for patients with anatomical
abnormalities in the spinal area.
Given the extensive experience in our center with TENS (> 700 patients treated)
and SCS for refractory angina pectoris (>130 patients treated), it seems
unlikely that SENS has a higher complication rate than SCS or is less effective
than SCS or TENS.
In preparation for a large multi-center trial on the efficacy and safety of
SENS for chronic intractable angina pectoris, we want to conduct a pilot,
explorative trial to assess the feasibility, safety and efficacy of SENS
implantation in this patient group.

In preparation for a large multi-center trial on the efficacy and safety of
SENS for chronic intractable angina pectoris, we want to conduct a pilot,
explorative trial to assess the feasibility, safety and efficacy of SENS
implantation in this patient group.

This is a monocenter (UMCG), prospective, open label, explorative study. A
limited total number of 10 patients meeting all inclusion and exclusion
criteria, will be included in the study.

From previous studies with neurostimulation for angina pectoris by SCS, it is
our experience that patients have a learning curve of about 6 weeks to get
entirely familiar with the use of the neurostimulation device. Study period is
therefore fixed at 8 weeks.

The SENS treatment incorporates subcutaneous implantation of 2 octopolar
electrode-leads and an implantable pulse generator (IPG). Implantation will be
performed under anesthesiological surveillance and local anesthesia. Proper
lead placement is verified through intra-operative trial stimulation, in which
paresthesias are experienced by the patient covering the field of chest pain.
A separate subcutaneous pocket for IPG placement will be made at the left
sub-clavicular site.
The two electrode-leads will subcutaneously be tunneled to this pocket site and
connected to the IPG
At the end of the operative procedure the IPG settings (pulse width, frequency
and intensity of the electrical pulses) will be programmed.
The patient is regarded to stimulate three times one hour every day, with
regular periods in between. In addition, if a patient is experiencing an
anginal attack, he/she is advised to rest, to activate the stimulator and
proceed stimulating for 10 minutes. The patient is allowed to stimulate before
the onset of an anginal attack and at circumstances (exercise) at which he
knows anginal attacks are provoked.

A study-visit is planned at baseline and at 8 weeks after SENS implantation.
Patients are in any case candidates for neurostimulation treatment, and usual
care includes a visit prior to implantation and a viste at 6-8 weeks
post-implantation. Extra burden associated with study participation includes
administration of a questionnaire (2x), a patientdiary (2x) and performing a
bicycle-exercisetest (2x).

The risks of implantatie are considered equal to those associated with the
customary SCS implantationprocedure.
Except the risks for operations in general (as infection or bleeding) there are
risks associated with the implanted system, such as:
- repulsion of the implantated devices
- undesirable changes in stimulation through:
o changes in electrode position
o changes in the tissue around the electrodes
o lead defects

These evens may require adjustment of the stimulationparameters or
re-operation.