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).