Multimodal PSOCT-NIRS catheter for guided ablation of atrial fibrillation

Figures

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  Fig. 1. In the CAD cross-section (a), the components of the probe are labeled: (1) glass window, (2) GRIN lens of the PSOCT probe, (3) irrigation ports, (4) radiofrequency electrode, (5) NIRS fiber, (6) thermocouple, and (7) torque coil. Band electrodes are included in the fabrication but are not shown. Panel (b) provides a head-on view of the glued window glass and the circumferential NIRS fibers, which are also labeled as (5) in panel (c). The scale bar measures 1 mm. In panel (d), the entire tip is divided into the insert electrode (8) and the NIRS shell (9). This panel reveals the exposed fibers. In panel (e), the two components are securely fixed together.

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  Fig. 2. Panels (a) and (b) show example birefringence and intensity images, respectively, of a polycarbonate phantom. Birefringence increases along the length of the phantom as taper width decreases, whereas scattering intensity remains unchanged. A strong linear relationship exists between birefringence and the inverse of taper width [red line in panel (c)], with an R2 value of 0.960. Intensity has poor correlation with taper width [black line in panel (c)] with an R2 value of 0.212.

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  Fig. 3. Simultaneous measurements indicate that PSOCT and NIRS can detect tissue contact when the left atrium is submerged in blood. The conventional OCT (a)–(c) and birefringence (d)–(f) images display the blood pool and the tissue as the catheter approaches tissue contact. The blood appears homogenous and nonbirefringent (a), (d). The lower birefringent endocardium (red arrow) and the higher birefringent myocardium (yellow arrow) are partially in frame as the catheter makes partial contact with the atrial wall (b), (e). During complete wall contact, the images show a heterogeneous structure in the myocardium (yellow arrow). The NIRS relative reflectance (g)–(i) is of lower magnitude when the catheter is floating in the blood pool compared with tissue contact. In addition, the absorbance peak from blood constitutes a larger proportion of the signal, as annotated with a blue arrow in panels (g)–(h).

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  Fig. 4. Four lesions were ablated in the swine atrium ex vivo. Each lesion was treated for 60 s, with different powers (5, 10, 15, and 20 W). The patterns measured by optical metrics (a)–(c) and the standard impedance metric (d) follow trends related to ablation power. Birefringence (a) decreases as ordered proteins denature with energy delivery, and the 20 W lesion also decreases the most and the fastest. Intensity increases as the scattering properties of the tissue change (b), and the 20 W lesion increases the most and the fastest. The NIRS LOI (c) increases as spectral changes indicate lesion formation. Impedance (d) decreases more as higher energy is deposited. The TTC staining reveals the treated region in pale white (black arrows), whereas untreated regions appear a deeper red (light blue arrows). All lesions were ablated in the same area of the left atrium in the same swine heart, and the scale bar is 5 mm. However, the 5 W lesion did not leave a visible treated lesion in the atrial wall. The optically derived metrics (a)–(c) show minimal change during the 5 W energy delivery.