SENTINEL Catheter
Another catheter was an optical catheter which was a Sentinel catheter
(SENTINEL Catheter, Catharos Medical Systems, Campbell, California) with
a fiber-optic probe. This designed catheter contains aspiration lumen
and basket tip as well as fiber optic sensors. This Catharos Sentinel
system detected signal changes upon contrast injection to the CS. The
mechanism was associated with signal variation in a way that after CS
administration of the contrast agent, the alteration in hematocrit (Hct)
was detected by fiber optic sensors located in the catheter tip. A
guidewire (Terumo Corp., Japan) was used for engaging CS and the
Sentinel catheter was introduced to the CS through GlideWire.
Fluoroscopic images were used to confirm the proper location of the
expanded basket in CS (Figure 13 ). The contrast removal rate
was calculated using a spectrophotometric assay. In order to assess the
safety of this method, the hearts of two canines were fixed with
formaldehyde. The gross pathology report on CS integrity and other major
branches including great and middle cardiac veins as well as anterior
interventricular vein revealed all lumens were patent and no evidence of
hemorrhage or thrombosis had been observed. Although some places of
superficial endothelial cell disruption were found on histological view,
the underlying stroma was normal. Additionally, they found insignificant
mural inflammation in their samples. Their study was the first in the
literature to evaluate the usage of endovascular detection methods for
contrast removal. By defining signal to noise ratio as s trigger point,
they also indicated this system is an active method for contrast removal
and no interventionist’s attention is required during the procedure.
However, some points should be considered. Despite the reflectance
signal for contrast aspiration being somewhat noisy, signal detection
could be differentiated from baseline signals. The aspiration threshold
was set to sown-crossing four volts in their study, but it was possible
that some portion of the contrast agent escaped from the collection
before crossing this threshold. Therefore, the implementation of exact
algorithms to detect this falling edge in an automatic manner rather
than by noise seems
pivotal (88).